1990 Accord - what is turning on the cooling fan?
Tom Karolyshyn
ultimately drains the battery. This happens even after the car has been
sitting for a couple of days, so this is not the normal scenario where the
fan runs after turning the car off. By the way, the reason it sits for a
couple of days at a time is because I can't drive it until I fix this
problem.
I've been through the factory service manuals and electrical troubleshooting
manuals (and I'm very comfortable with a voltmeter), but unfortunately the
manuals are vague enough in this area to keep me puzzled. Everything seems
to work ok otherwise, i.e., when the car is running, both fans turn on when
I press the A/C button on the dash.
There is a module called the "cooling fan timer" under the dash which
supplies +12v to the cooling fan relay. And the ground side of the relay
can be generated from multiple sources. When this problem is happening
(which is intermittent), I see +12v on the relay connector coming from this
timer, so naturally the cooling fan relay engages, which turns on the fan.
I'm trying to determine if the timer is at fault for supplying +12v for no
reason at all, or if it's being told to supply +12v by something else. I'm
inclined to replace the timer, but I don't have any hard proof that it alone
is the culprit.
Anyone have any stories or insight to share on this topic?
Anderson, Ryan Drake
My fan comes on and off several times - instead of one time like it should.
I think maybe the culprit is the ECT switch B??
"Tom Karolyshyn" <tkar...@cisco.com> wrote in message
news:1000131049.895924@sj-nntpcache-3...
Tom Karolyshyn
I'm asking for help.
In your case, you'll need to determine whether it is your cooling fan (pass
side) or condenser fan (drivers side) which is turning on at random. In my
case, it's the cooling fan.
I believe ECT switch B drives the condenser fan, but I don't have my manual
with me, so I can't say for sure.
"Anderson, Ryan Drake" <dra...@bellsouth.net> wrote in message
news:2d6n7.41486$VX3.1...@e3500-atl1.usenetserver.com...
Arthur Russell
Here's some info I posted to another fellow having trouble here not
long ago...it's almost verbatim from the service book:
> If the coolant temperature is above ~108C (226F) when the ignition is
> turned off, the condenser fan will run for ~15 minutes to cool the
> engine. The coolant temperature sensor involved (it's actually a switch,
> "switch B") is behind the water outlet cover beneath the distributor.
> With the car off, disconnect the 2-pin connector from the switch, and
> jump the wiring harness side. The condenser fan should come on. The
> timer control box is located in the driver's foot well area, on the left
> wall, it's a small, stand alone relay box with an 8-pin connector.
I just went out and played with my 91 Accord to verify this info, and
here's what I found:
The car's been sitting for a day. I opened the hood, and jumped the two
pins on temp switch B (this switch is easy to get at, it is on the metal
housing attached to the engine that couples with the large, upper,
radiator hose. It's pink, and the mating connector on the wiring harness
is green. It's below the distributor, but more towards the front of the
car). Nothing happened. Then, I switched the ignition on for a moment,
and turned it back off. I re-connected the pins on the connector, and
the engine cooling fan came on. I learned two things:
1) The book didn't mention it, but apparently once the timer has
expired, switch B won't turn any fans on.
2) The fan timer unit turns the engine fan on, with the ignition off and
switch B closed, not the (A/C, sic) condenser fan, as the book suggests.
This was so strange, I read on a bit in the book, and also looked a bit
longer at the wiring diagram. Then I went back out to the car, and made
the following discoveries:
I disconnected cooling switch A, and jumped the two pins inside (this
switch is under the distributor as well, but towards the firewall. It is
on a different metal housing, which accepts the large, lower radiator
hose. It also has a pink shell and a green mating connector) Then, I
turned the ignition on. Both the engine cooling fan, and the condenser
fan switched on. I switched the ignition off, and, while leaving switch
A shorted, I jumped the two pins on temp switch B. This time, the
condenser fan did NOT run, and instead the engine cooling fan did (which
is consistent with what the manual says). From a temperature standpoint,
witch A engages before switch B, so my first test was something the
system doesn't expect.
In any case, based on this info, you should be able to quickly home in
on whether either of your switches are faulty, or if the timer control
is bad. By the way, when your car is sitting and the fan comes on all by
itself, which fan is it? The engine fan in on the passenger side, and
the condenser fan is on the driver side.
Good luck,
Arthur
Arthur Russell
confusing...but the data is right (just not my conclusions.) The short
story is that both times (with or without switch A shorted) the engine
cooling fan came on by itself. So, unless someone sees something I'm
doing wrong, the Helm book has an error here. Switch B turns on the
engine cooling fan, not the condenser.
As far as I can tell, the only wires that connect this system to other
electronics are the A/C clutch signal (an input to this circuit), the
wire to the A/C diode (an output from this circuit), and the switched
ground from temp switch A (which is most likely only an output from this
circuit) The timer should ignore the A/C clutch input with the ignition
off. (BTW, if the clutch were engaging with the ignition off, it would
also drain the battery)
I see from your subsequent post that it's your engine fan that's coming
on at strange times. I'd definitely see if switch B is doing it, and if
not, try to get a replacement fan control timer.
Good luck,
Arthur
P.S. Additionally, it's possible that there were some changes in the
control of this stuff from the '90 to '91 years, but I'd bet they're the
same.
Tom Karolyshyn
language".
You've given me a few things to explore. I'll try some things tonight.
Unfortunately, I believe I already verified that thermo switch "A" is
correctly the one closer to my firewall and thermo switch "B" is the one on
the radiator hose gooseneck (towards the front). It is possible that Honda
swapped them between 1990 & 1991, yet the 1991 manuals weren't updated. My
manuals are definitely 1990. However, I must also say that I've tried sooo
many things that I've lost track. I'll double-check.
As for what could possibly trigger the fan to start, there is another wire
on the schematic - feeding the BLU ground connection - from the computer.
Yet another variable. I'm very confused as to why both the +12v AND the
ground are "controlled". In other words, I don't know if Honda simply uses
the timer to toggle the +12v on/off to control the fan, or if the ground
connection somehow factors into the equation. You'll notice that the ground
side of the relay is not a hard-wired ground; it (BLU) must be delivered
from one of a few different sources. No ground, no completed circuit. This
is what I mean about another variable.
I did pick up the Honda "Electrical Troubleshooting Manual". I don't know
whether it's a help or a hinderance. For one thing, it states that the
cooling timer should only run for 2 minutes after shutting off the car.
This conflicts with the 15 minutes printed elsewhere.
And lastly, I don't know if a conversation this deep warrants moving it
off-line or if other folks find this helpful. I'm new to this newsgroup.
I'll let you (and the other users) be the judge.
Regards,
Tom
"Arthur Russell" <a...@NOSPAMbellatlantic.net> wrote in message
news:3B9D0888...@NOSPAMbellatlantic.net...
Anderson, Ryan Drake
> I did pick up the Honda "Electrical Troubleshooting Manual". I don't know
> whether it's a help or a hinderance. For one thing, it states that the
> cooling timer should only run for 2 minutes after shutting off the car.
> This conflicts with the 15 minutes printed elsewhere.
The 2 minutes is definetly incorrect.
> And lastly, I don't know if a conversation this deep warrants moving it
> off-line or if other folks find this helpful. I'm new to this newsgroup.
> I'll let you (and the other users) be the judge.
Please keep posting online! This is exactly what the newsgroup is here for!
Arthur Russell
you mean. The manual for the 91 also states that the timer interval is 2
minutes. The section that discusses the condenser fan talks about an oil
temperature switch, which I don't know of (don't think it exists) It's
also pretty hap-hazard describing how things work. No mention of why the
fan timer would want to pull the blue wire to ground, for example, but
they say it can do this.
It does state that if a relay coil has power supplied (controlled by the
timer unit exclusively), the blue wire will fire the relay if it is
pulled to ground. Switch A can pull blue to ground all by itself.
Similarly, the combination of the A/C button being ON and the blower set
to some ON position will pull the blue wire to ground through the A/C
diode. The timer can ground blue (perhaps it runs the fans for a bit of
time after switch B opens, or in case switch B calls for cooling, but
switch A is defective?) Finally, the ECU can pull blue to ground, as
well as monitor blue for something else pulling it down. The interesting
point here is that the only thing that can supply +batt to the other
side of the two fan control relays is the fan timer unit. When I went
out and tried shorting switch A, and switch B, nothing happened until I
cycled the ignition on and off (thus setting the timer). It seems like
the problem must be your fan timer unit.
-Arthur
P.S. How's your cruise control working? It uses the same ground as the
fan timer. Faulty ground could cause some of these problems, by the way.
Tom Karolyshyn
But let me first say thanks for the info about the 2 minutes being
incorrect. And I agree that a bad ground can cause weirdness like this. I
hope to explore that further as well. And lastly, I have no idea if my
cruise control works; I haven't had the car on the road for any amount of
time.
Here are my findings from last night in no particular order:
1) The car was idle all day. I connected the battery and the cooling fan
turned on immediately. I figured Aha! I'll catch it in the act. My problem
is intermittent, making it more difficult to troubleshoot. I disconnected
the battery as a knee-jerk reaction. I then removed the connector to the
frontmost thermo sensor ("B", but more on that later). Reconnected the
battery. No fan. Then I reconnected the thermo-sensor and still no fan.
So my test was not productive. I think disconnecting the battery "undid"
something. I'll try again another day.
2) After that, I duplicated your (Arthur) first test with the same results.
Jumpered front sensor B and nothing happened. Then turned the IGN on/off,
rejumpered front sensor B, and cooling fan came on. Continued to stay on
til the timer expired.
3) To confirm/refute your suspicion about the manual being wrong with regard
to sensors A & B, I got out my ohmmeter and tracked down the path of the BLU
wire which is common to both relays and the "A" sensor. The "A"
thermo-sensor is *definitely* the one in the rear. It has the common wire
to both relays. It's possible that your 1991 is different, but my 1990 is
definitely this way.
4) I confirmed that the reason the cooling fan comes on after the IGN
on/off, with the B (front) sensor jumpered, is becuase the timer is
supplying +12v YEL to the cooling fan relay. The +12v disappears after it
times out.
5) This lead from sensor B (front) into the timer normally sits at +6.84v
relative to GND when the sensor contacts are open (normal mode).
6) The BLU wire which connects a few different things has no relative
voltage to GND normally. It does measure approx 3.74v from the pos battery
terminal nominally. It gets grounded obviously when the rear A sensor
closes.
Tom
SASCHOCH
<tkar...@cisco.com> writes:
>And lastly, I don't know if a conversation this deep warrants moving it
>off-line or if other folks find this helpful. I'm new to this newsgroup.
>I'll let you (and the other users) be the judge.
>
>Regards,
>Tom
Yes, Tom this IS appropriate NG usage. Keep it going so the rest of us will
learn.
-Steve
Anderson, Ryan Drake
engine off. I'm in Alabama and this summer has been in the 90s - the fan
should come on almost after every drive, but it hasn't been. And when it
does, it stays on for maybe 20 seconds and then goes off. And usually comes
back on a few seconds later. Sometimes, when it shuts off, you can hear it
try to start back up - like somebody flips the light switch on and back off
real quick.
I turned the ignition on for a few seconds then turned it off. Then I
unplugged switch B and jumped it. Nothing happened. From what I've been
reading, it should have came on. Since it didn't, what does this indicate?
"Tom Karolyshyn" <tkar...@cisco.com> wrote in message
news:1000216034.61490@sj-nntpcache-5...
billk...@snotmail.com
"Anderson, Ryan Drake" <dra...@bellsouth.net> wrote:
> Ok, I have been having problems with my fan coming on after I turn the
> engine off. I'm in Alabama and this summer has been in the 90s - the fan
> should come on almost after every drive, but it hasn't been. And when it
> does, it stays on for maybe 20 seconds and then goes off. And usually comes
> back on a few seconds later. Sometimes, when it shuts off, you can hear it
> try to start back up - like somebody flips the light switch on and back off
> real quick.
>
> I turned the ignition on for a few seconds then turned it off. Then I
> unplugged switch B and jumped it. Nothing happened. From what I've been
> reading, it should have came on. Since it didn't, what does this indicate?
>
You might check to make sure you don't have air trapped in the cooling system.
With everything warmed up, crack the bleed bolt near the thermostat
housing. I think it takes a 12mm wrench. Make sure you get a steady stream
of coolant, then close tight.
This may not be the problem, but it is free and easy to check.
--
To email me, change snot to hot
Tom Karolyshyn
mind off things) I hooked up the battery and the cooling fan started right
up! Rather than take a chance of losing this scenario by disconnecting the
battery, I immediately jumped into unplugging things to eliminate the
source. I unplugged:
1) thermo sensor "A"
2) thermo sensor "B"
3) cooling relay
4) condenser relay
5) diode
6) A/C pressure switch
Unplugging all of these items had no effect. The fan continued to spin!!!
And it continued to spin until I unplugged the fan timer unit itself. This
supplies the +12v, so I fully expected it to stop. When I reconnected the
fan timer, the fan started up again.
But before jumping to the obvious conclusion that my fan timer is bad and
potentially spending money on one for nothing, I'd appreciate your opinions.
Option 1) Replace the fan timer - Any idea what a fan timer costs?
Option 2) There is 1 remaining source that could pull down the BLU wire, and
that is the ECU. Could it be suspect? There appear to be 2 ECU
connections, which is bizarre, but removing the diode only killed one of
them. I have no idea why the ECU even plays a role here.
Option 3) There is a BLK ground wire to the fan timer. Could a bad ground
contribute to this particular problem?
So in your opinions, is it worth checking into further or after
disconnecting almost everything, is this an open and shut case?
Thanks,
Tom
Tom Karolyshyn
give any confirmed "correct" information. Anything I say about how my car
works could be totally wrong.
You may want to provide us with some add'l info and we'll see what we can
do.
- Does your car have A/C?
- Are you clear about which fan is which? It's unclear if you use the word
"fan"; there are 2 of them. The "cooling fan" is on the pass side and the
"condenser fan" is on the drivers side.
- I'd like to also confirm that when you reference "switch B" that you mean
the front-most thermo switch?
I've been into this so deep that I've come to realize these distinctions are
pretty critical.
Tom
"Anderson, Ryan Drake" <dra...@bellsouth.net> wrote in message
news:TPAn7.179421$ZJ.15...@e3500-atl2.usenetserver.com...
Anderson, Ryan Drake
> I'd love to offer an answer, but until I get my problem resolved, I can't
> give any confirmed "correct" information. Anything I say about how my car
> works could be totally wrong.
>
> You may want to provide us with some add'l info and we'll see what we can
> do.
>
> - Does your car have A/C?
Sure.
> - Are you clear about which fan is which? It's unclear if you use the
word
> "fan"; there are 2 of them. The "cooling fan" is on the pass side and the
> "condenser fan" is on the drivers side.
I'm very clear. It's the passenger side fan.
> - I'd like to also confirm that when you reference "switch B" that you
mean
> the front-most thermo switch?
I don't really know exactly what a 'front-most thermo switch' is. I call it
ECT Switch B - what my 93 Accord Service Manual refers to it as.
> I've been into this so deep that I've come to realize these distinctions
are
> pretty critical.
I just got back from town and popped the hood. After about a minute, the
fan came on. Maybe 20 seconds later it went off and before it completely
stopped spinning it was like someone switched the power on to it for a split
second because you could hear it spin back up then immediately cease.
> Tom
>
Tom Karolyshyn
it
> ECT Switch B - what my 93 Accord Service Manual refers to it as.
Sorry. There are 2 thermo/temperature switches on the engine which monitor
coolant temperature. Relative to each other, one ("B") is located towards
the front of the engine compartment and the other ("A") is located behind
it. Arthur did an excellent job of describing them in one of the early
posts.
> I just got back from town and popped the hood. After about a minute, the
> fan came on. Maybe 20 seconds later it went off and before it completely
> stopped spinning it was like someone switched the power on to it for a
split
> second because you could hear it spin back up then immediately cease.
I honestly cannot say if this behavior is normal, because as I said, my
system is messed up and I'm still trying to learn how it should work.
I just ordered a fan timer from Honda. But all parts deliveries are
obviously impacted by the airline/airport status, so I don't know how soon
I'll get the part. I'll let you know if it solves my problem, and I may
possibly be in a position to answer some questions about what "should" and
"shouldn't" happen at that point.
Regards,
Tom
Arthur Russell
agreement with you. Switch A is towards the firewall, and switch A
serves to short the blue node to ground.
> 3) To confirm/refute your suspicion about the manual being wrong with regard
> to sensors A & B, I got out my ohmmeter and tracked down the path of the BLU
> wire which is common to both relays and the "A" sensor. The "A"
> thermo-sensor is *definitely* the one in the rear. It has the common wire
> to both relays. It's possible that your 1991 is different, but my 1990 is
> definitely this way.
>
Now I see your post from 10:38AM today (9/12/01), so I'll comment on
that here:
1) with the radiator fan relay removed, (it looks like that's one of the
items in your list,) there should be no way for the cooling fan to be
running, since the current path for the fan motor is through this relay.
That's a real puzzle.
2) In any case, even with the diode, condenser relay, and switch A
removed, the ECU can pull down the blue wire to ground. If the timer is
supplying +12 to the relay coil, and the ECU pulls down the blue wire,
the fan will run. When you remove the timer, the fan stopped; any other
outcome should be impossible, since the fan timer unit is the only thing
that can supply hot to the radiator fan relay's coil (unless you have a
short or open in the control wiring, I believe this has to be the case.)
Would you look carefully through your wiring diagram again, and see if
there is anything that can supply +12 to the radiator fan's relay coil?
(yellow wire in my book) If not, the timer is definitely supplying power
when it shouldn't be. If you can just prove that the timer considers no
additional external inputs in determining whether to power the fan relay
coil with +12, you have your problem solved...get a replacement timer
from somewhere.
Good luck,
Arthur
Tom Karolyshyn
job; I appreciate the proofread. Obviously I've been in a flurry of
troubleshooting activity and posting the results are non-trivial. Not to
mention that my heart is in NYC & Washington D.C. All of this Honda talk
can seem trivial at times, but then again, life must go on.
> 1) with the radiator fan relay removed, (it looks like that's one of the
> items in your list,) there should be no way for the cooling fan to be
> running, since the current path for the fan motor is through this relay.
> That's a real puzzle.
The error, or omission that I made was relative to your point #1. With the
cooling fan relay removed, as you said, it is *not* possible for the fan to
run. This is very true. What I failed to mention was that I improvised a
bit, in an effort to spare my battery, which has been discharged and
recharged possibly too many times already. Immediately after seeing my
cooling fan spin, I substituted a +12v test light to indicate whether the
fan would be "on" or "off". I did this at after removing the cooling fan
relay. I connected this test light to the YEL +12v lead coming out of the
timer. Physically, I grounded the test light on a body bolt near the engine
fuse compartment, and plugged the test light into the connector that the
cooling fan relay normally sits. This way I was able to monitor the +12v
signal YEL from the timer that would be otherwise energizing the relay, and
thus turning on the fan.
> Would you look carefully through your wiring diagram again, and see if
> there is anything that can supply +12 to the radiator fan's relay coil?
> (yellow wire in my book) If not, the timer is definitely supplying power
You are correct. There is nothing else that can supply +12v to the cooling
fan relay coil. If the cooling fan relay is removed, the cooling fan can't
operate.
But your questions have raised a question with this test light technique I
used. Is it valid for me to connect the test light GND to body GND, or
should I have attached the test light GND to the BLU wire? I think the BLU
wire would be the more accurate test.
Regardless, I've gone ahead and ordered the fan timer from Honda. The last
thing I did was check for continuity in the black ground connection from the
fan timer to the body (GND point G401), and it checked out ok. Everything
seems to point to the timer. And I've spent enough time on the analysis at
this point. The ROI of my personal time is diminishing. There's a much
bigger return on investment for me right now if I replace this component and
check the results. I'll let you know.
Tom
Arthur Russell
> cooling fan relay removed, as you said, it is *not* possible for the fan to
> run. This is very true. What I failed to mention was that I improvised a
> bit, in an effort to spare my battery, which has been discharged and
> recharged possibly too many times already. Immediately after seeing my
> cooling fan spin, I substituted a +12v test light to indicate whether the
> fan would be "on" or "off". I did this at after removing the cooling fan
> relay. I connected this test light to the YEL +12v lead coming out of the
> timer. Physically, I grounded the test light on a body bolt near the engine
> fuse compartment, and plugged the test light into the connector that the
> cooling fan relay normally sits. This way I was able to monitor the +12v
> signal YEL from the timer that would be otherwise energizing the relay, and
> thus turning on the fan.
I would recommend connecting the test light to the plug to the engine
cooling fan. If you insert the test lamp between chassis ground and the
YELLOW wire from the timer, you're only going to get half the story
(that is, whether the timer *would allow* the engine fan to run if the
coil (-) were grounded. Again, the negative side of the coil can be
grounded by a few things, probably Switch A, and the timer unit itself
(possibly in conjunction with switch B) are the most likely candidates.
The fact that the timer puts +12 on the yellow node does not mean that
the relay would be energized. Furthermore, you can't measure the voltage
on the blue node without a relay present and know what would happen to
the fan relay, since the relay coil presents an impedance between the
nodes, and allows current to flow. With no current flowing into the Blue
node from the relay coil, it's very possible that node's voltage will be
near ground, even though the relay wouldn't fire were it plugged in.
> > Would you look carefully through your wiring diagram again, and see if
> > there is anything that can supply +12 to the radiator fan's relay coil?
> > (yellow wire in my book) If not, the timer is definitely supplying power
>
> You are correct. There is nothing else that can supply +12v to the cooling
> fan relay coil. If the cooling fan relay is removed, the cooling fan can't
> operate.
>
> But your questions have raised a question with this test light technique I
> used. Is it valid for me to connect the test light GND to body GND, or
> should I have attached the test light GND to the BLU wire? I think the BLU
> wire would be the more accurate test.
I think you're right. If you want to use the test light between the
yellow and blue nodes, then make sure the light draws at least 10mA or
something. You can check it out with a (series) ammeter when you hook it
up to the battery. If it doesn't (high impedance light) then I would put
a ~1.2kohm resistor in parallel with the light. This will remove any
concern that various pull-up and pull-down resistors in the various
components hooked to those nodes are falsely causing the light to
illuminate.
Good luck,
-Arthur
P.S. I know what you mean about posting on RAMH in times like these. I'm
starting a new job Monday, but I've had too much time sitting around
watching Peter Jennings and listening to NPR. RAMH can be a nice way to
get away.
Tom Karolyshyn
Got it from the dealer. Around $90. I left the battery connected overnight
and all weekend, along with every relay, etc. attached.
The battery did not drain!
This is the first time I've made it overnight, nevermind an entire weekend,
without killing the battery. Over the weekend, I drove the car about 5
times and a couple of times the cooling fan continued to run after I shut
off the car. I waited anxiously for it to shut off, and both times it
eventually did. The times varied between 2-5 minutes. A couple of other
times, when I thought the engine was pretty hot, the cooling fan didn't run
after shutting it off. So about all I can say is the cooling fan activity
is that it may be logical when analyzing the schematics, but it isn't
particularly predictable from the owner's point of view, i.e., standing
outside the car while waiting and listening.
Arthur, your point is right on the money about where to attach the test
light. I should have plugged it into the actual cooling fan connection.
That would be the best and most accurate place to test. Unfortunately, that
particular connector (if you're familiar with it) is very difficult to
access, so I took the easy way out.
Thank you all very, very much for your feedback and support. Hopefully my
endeavor has shed some light on things, and my solution will help someone
else out. I suspect there was a leaky diode or some other component
breakdown within the fan time unit. I popped open my old one (easy to do)
and inside is a circuit board with a couple of IC's (chips), and many
diodes, transistors, and capacitors. I couldn't begin to figure out how it
works without a schematic. And I've run out of time and energy.
So though I haven't completely profiled the action/reaction of the fan timer
circuit (and probably will never completely understand it), I think the
dialogs we have had can certainly provide someone with a step up on
diagnosing their own problem.
This is a terrific newsgroup and I hope to contribute in the future. I
thank you again.
Regards,
Tom
billk...@snotmail.com
>
> Thank you all very, very much for your feedback and support. Hopefully my
> endeavor has shed some light on things, and my solution will help someone
> else out. I suspect there was a leaky diode or some other component
> breakdown within the fan time unit. I popped open my old one (easy to do)
> and inside is a circuit board with a couple of IC's (chips), and many
> diodes, transistors, and capacitors. I couldn't begin to figure out how it
> works without a schematic. And I've run out of time and energy.
>
PN on the timer was 37740-PEO-661 made by Shindengen.
Was yours the same?
Ricky Spartacus
If, IGNITION OFF
then, +0V outputs to (yel) condenser fan relay.
then, +0V outputs to (yel/wht) radiator fan relay.
If, IGNITION ON
then, +12V output to (yel) condenser fan relay regardless.
then, +12V output to (yel/wht) radiator fan relay regardless.
IF, SWITCH B CLOSES (with IGN OFF)
then, GND outputs to (blu) or, all relays for 15-1/4 min.
then, +12V output to (yel) or, condenser fan relay for 15-1/4 min.
then, +0V outputs to (yel/wht) or, radiator fan relay.
If, SWITCH B CLOSES (with IGN ON)
then, Nothing happens.
If, SWITCH A CLOSES (with IGN ON)
then, Both fans run
If, SWITCH A CLOSES (with IGN on start, ACC or OFF)
then, both fans stop
Fan only runs 15 min once. Turn on ignition resets timer.
Disconnecting any timer power supply stops fan. After connecting
battery, switch B has no effect until ignition turn on and off. Static
electricity can alter the IC. In some cases the IC can come back to
life a week after properly grounded.
In short, if you catch your radiator fan on, blue and yel/white should
be off when igniton is off. If not, timer is bad but only if you
contain it by removing pin blue and yel/white and then conduct the on
car test or do it all on a test bench. You should do in a controlled
enviroment like a test bench.
-RS
PS> disconnecting relay should stop fan unless something has changed.
*Data obtain from timer was hooked into a mini-lab on a test bench.
Ricky Spartacus
Instead of using a test light, I simply used an LED. Works fine.
By the way you said, "I switched the ignition off, and, while leaving
switch
A shorted, I jumped the two pins on temp switch B. This time, the
condenser fan did NOT run, and instead the engine cooling fan did
(which
is consistent with what the manual says)."
This isn't what the Helm manual printed, please let me know the page.
Doing the above should only turn condenser fan on.
-RS
Tom Karolyshyn
> PN on the timer was 37740-PEO-661 made by Shindengen.
> Was yours the same?
The part # on my timer is 37740-PT3-A01, by Shindengen as well. I checked
D7 but there are no obvious signs of distress to it or for that matter any
of the components. My symptoms were intermittent so I'm not surprised I
didn't see anything fried.
Arthur Russell
Yeah, you're right. My manual says the timer will fire the condenser fan
(p. 23-99) also. However, I believe that when I have looked to see which
fan was running after parking the car, the engine fan was the one
running (without unplugging anything etc.) I had a bad bearing in that
fan, and as I recall, I noticed the bad bearing both while driving, and
when the car was parked. I figured the book description to have a typo
or an error about this. It's been awhile since I looked in to any of
this though, so maybe I'm remembering wrong.
I posted a follow up post (9/10/01 3pm) that clarified what I had meant
to say. However, the fact remains that my timer does not appear to run
the condenser fan, only the engine fan. That's why I said I thought the
book had an error. Can you verify that your condenser fan is the one
running with the ignition off?
-Arthur
P.S. The LED is fine to use, except you also need a biasing resistor.
Otherwise your LED will draw too much current as it attempts to limit
the voltage across it to a volt and a half or so.
