Help, A/C blower motor won't turn off
np6
day I turned the car off and the a/c blower motor (fan) kept running
even after I took the key out. I had to pull the fuse to shut it off.
The a/c and heater seem to work ok, it's just that the fan won't turn
off. I took it to a local mechanic who said I need a new HVAC control
head. The dealer has to order it, and it costs $700! Can it really
be that big of a problem to fix a blower motor that won't shut off?
I'm now popping the hood and putting the fuse in before I drive, then
pulling the fuse when I'm done. For $700, I'm thinking of building
some kind of switch that runs from the fuse to outside the hood so I
don't have to pop the hood. Any ideas?
DougW
np6 did pass the time by typing:
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
Tell the mechanic to get bent. :)
From your description and the base Limited, prolly the auto. So let's
start there.
I'm betting you have a stuck blower motor relay. That's the most
likely failure point.
Problem is I think the relay is in the control head. Should
be real close to the fan speed switch. Follow the trace back from
pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times
it might free up.
This schematic is very poor on that module, it almost looks like a
replacable 5 pin style relay, like a fog relay.
My scanner is down, but if you want the schematic just post a reply
with "DougW" in the subject line and I'll catch it easier.
--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Mike Romain
Maybe the sensor has failed?
Try a multimeter on it to see if it has a connection when cold, if so
replace it.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Lon Stowell
The blower motor is controlled by the ATC controls with
speed feedback. You may want to disconnect the battery
as it resets the control completely. This *could* be
as trivial as the high speed relay.
With the fuse in, turn it on, then turn the motor off.
Then pull the A/C fault codes.
Push AC and RECIRC at the same time. While doing this,
rotate the Temp knob one click Clockwise. This should
light all indicators as long if you keep your fingers
on the AC/RECIRC.
Take your fingers off the AC/RECIRC and the display should
go to 00, ready to pull codes. Push *either* the AC or
RECIRC but not both. The little stickman appears indicating
you are now in Diagnostic Mode. If the display stays at
00, the thing doesn't *think* the ATC module is bad. Push
the same button AC *or* RECIRC to step codes.
If you see fault 25 or 29, the ATC is bad and the rest of
any codes are bogus. Code 08 would indicate motor feedback
is too high, possibly not the ATC. 12 means the fan control
knob is bad. 16 means not enough motor feedback.
40 means at some point the feedback was too high but not
at the present. 48 is historical feedback too low. 61 means
the ATC was bad but thinks it is ok now.
To clear codes, push AC *or* RECIRC and hold for 3-4 seconds
until 2 bars appear on the display. Only clears codes
33 and higher.
You can pull detailed status by starting all over, push
AC and RECIRC, one click CW. This should turn on the stick
man and set to 00 or an uncleared fault code.
Step the tests by rotating the knob CW. OC is open ckt,
SC is short.
As you step the display with the knob, to read the inputs,
press either AC or RECIRC.
To actually test the outputs, go back to Diag Mode with
the AC/RECIRC trick and one CW click.
Then select the test you want to run by turning the Temp Knob
CW and when it displays the number you want, push the AC
button to see the result.
Test No. What is checked Display
------- --------------- -------------------------
01 Blower Ctl Switch ?, OC, SC, 00-255
02 Blower Feedback ? 00-255
03 Blower Speed 00-255
04 Hi Speed Relay 00= off 01= on
If you push the RECIRC button during these, the value will
step and the motor should speed up/down.
And your warranty on this advice is roughly the same as
you paid for it.
Lon Stowell
> np6 did pass the time by typing:
>> I have a strange problem in my 94 Grand Cherokee Limited. The other
>> day I turned the car off and the a/c blower motor (fan) kept running
>> even after I took the key out. I had to pull the fuse to shut it off.
>
>
> Tell the mechanic to get bent. :)
>
> From your description and the base Limited, prolly the auto. So let's
> start there.
>
> I'm betting you have a stuck blower motor relay. That's the most
> likely failure point.
Note that this relay ain't thar unless the unit has ATC. And
caution that this is from a 95 FSM, so YMMV. Fuse 11 goes to
the high speed relay. If the relay is on, it feeds a full
battery voltage to the motor. If the relay is off, the motor
speed is controlled by battery voltage being fed to the
motor thru the Blower Power Module, which could also be bad.
Variable speed is controlled by
the BlowerPowerModule which gets its feed from the ATC
controller.
The Blower Power Module is allegedly along the right side
of the Instrument Panel, fairly near the Auto Temp Controls
on that panel.
The High Speed relay is located along the right hand side of
the HVAC under the dash. It gets a one-line feed from the
Auto Temp Controller.
Unfortunately neither the FSM nor the Body Diag has any
better location info or pictures or even remove and repair
for those two items.
L.W. Hughes III
DougW
L.W. (ßill) Hughes III did pass the time by typing:
> http://www.billhughes.com/blower.pdf
That's the relay.. It shows in my service book like
a relay on the control head but the numbering
indicates a much larger relay that would be mounted
to a board. The numbering in that diagram matches
and I'm fairly sure the guts didn't change from
93-95. Only some minor things like 4wheel disc brakes.
L.W. Hughes III
Lon Stowell
Bill's picture exactly matches where the FSM says
it is.... so swap that sucker. From the wiring
diagram, if you can get your hand in there it
should be possible to just pull the sucker to
test, since if you have ATC [which we forgot to
ask] the only thing that relay does is kick in
high speed, aka full battery voltage.
np6
have ATC, I forgot to state that. Unfortunately, I tried the various
suggestions and I still have the problem.
Lon Stowell <Lawn.S...@Komkast.net> wrote in message news:<JBpcb.570779$o%2.256178@sccrnsc02>...
>
> The blower motor is controlled by the ATC controls with
> speed feedback. You may want to disconnect the battery
> as it resets the control completely. This *could* be
> as trivial as the high speed relay.
I disconnected the battery and reconnected it, but the problem is
still there. I also tried to find the relay and hit it lightly. Not
sure I actually found it, but nothing I hit made any difference.
> With the fuse in, turn it on, then turn the motor off.
> Then pull the A/C fault codes.
I followed your detailed instructions (thanks) and this is what I got:
Code 08 and 48.
I then did the output tests you mentioned and this is what I got:
Test number 01 display 11
Test number 02, display 28
Test number 03, display 28
Test number 04, display 00
I then pushed the RECIRC button and the fan did speed up/down.
This is greek to me, but maybe it will tell you something.
I did see a fat juicy red wire going into the blower motor, just under
the glove compartment. I'm tempted to cut that and put an online
switch there, but when I mentioned this to the mechanic he said I
could produce a voltage spike that might screw up the computer that
controls everything and costs $2000. So, I'm hesitant to do anything
there but still thinking about putting a switch in place of the fuse
under the hood, that might be a safer thing to do.
I just hate paying $700 to turn off a #%@^$ fan. Just last month I
took it in to repair the CV joints, and they replaced both axles for
$800, which I was told was actually not too bad, but now for about the
same price I get to turn a fan off. Go figure.
Lon Stowell
> You guys are a wealth of information, thanks a lot. Oh, my Jeep does
> have ATC, I forgot to state that. Unfortunately, I tried the various
> suggestions and I still have the problem.
>
> Lon Stowell <Lawn.S...@Komkast.net> wrote in message news:<JBpcb.570779$o%2.256178@sccrnsc02>...
>
>>
>> The blower motor is controlled by the ATC controls with
>> speed feedback. You may want to disconnect the battery
>> as it resets the control completely. This *could* be
>> as trivial as the high speed relay.
>
> I disconnected the battery and reconnected it, but the problem is
> still there. I also tried to find the relay and hit it lightly. Not
> sure I actually found it, but nothing I hit made any difference.
>
>> With the fuse in, turn it on, then turn the motor off.
>> Then pull the A/C fault codes.
>
> I followed your detailed instructions (thanks) and this is what I got:
> Code 08 and 48.
08 means the feedback from the motor is too high which is wierd
unless there is a typo in my FSM, as it claims 48 means that at
some time in the past it was too low.
Purely a WAG, but if that relay was shorted or the power control
module was fried, I would expect solid fan speed and probably
an error because the commanded speed wouldn't match the actual
speed. Real jeep mechanics feel free to jump in any time here...
I'd pull the relay if you can...
>
> I then did the output tests you mentioned and this is what I got:
>
> Test number 01 display 11
> Test number 02, display 28
> Test number 03, display 28
> Test number 04, display 00 [it thinks the drive to the high
speed blower relay is off...]
>
> I then pushed the RECIRC button and the fan did speed up/down.
Hmmm. So whatever is wrong is such that the fan can be
controlled. To me this would eliminate the relay, but
I'd still pull it just because I am such a sceptical cuss.
And it looks like the power controller may indeed be able
to change the amount of battery voltage available to the
motor.... unless it is interacting with the high speed
relay which is easily checked by yanking the relay.
If the fan speed is still changeable, either the power
control module has a blown position in it [dunno likelihood]
or the output of the ATC module is tweaked, or the motor
itself has a bad feedback pickup, causing the ATC to freak
out.
To narrow it down, the only way I can see is to get under
there and check the voltages at a coupla points from the
ATC to the motor and back... after pulling the relay of course.
> I just hate paying $700 to turn off a #%@^$ fan. Just last month I
> took it in to repair the CV joints, and they replaced both axles for
> $800, which I was told was actually not too bad, but now for about the
> same price I get to turn a fan off. Go figure.
I actually bought the extended warranty [from a competitor yet]
on a used ZJ on the recommendation of the service manager
at the Jeep dealer [the ZJ itself was bought elsewhere] when
he told me how much it typically costs to make repairs on
the air conditioner, seat controls, etc. compared to the
more reasonable prices for running gear repairs. Worse than
a darned cadillac.
Stephen Cowell
"Lon Stowell" <Lawn.S...@Komkast.net> wrote in message
....
> Worse than
> a darned cadillac.
Having messed with a '93 Taurus with ATC, I'll never
own one again. Simple switch and resistor pack for me.
On topic, I'll bet it's the motor speed feedback, since
it did slow down during test and popped that code.
I wonder if that's replaceable, without changing the blower.
__
Steve
.
np6
> To narrow it down, the only way I can see is to get under
> there and check the voltages at a coupla points from the
> ATC to the motor and back... after pulling the relay of course.
After considering all the alternatives suggested on this board, I went
to a different mechanic (factory guy) and was able to talk with him
more intelligently about the problem. He diagnosed it as a bad blower
motor resistor, part #4720046. He replaced it for $127.05 parts and
$77 labor. And I thought only Uncle Sam would pay $127 for a
resistor. Imagine if it would have been a capacitor. Better than the
$700 the other guy wanted to charge to replace the entire HVAC control
head.
Thanks again for all your advice.
Lon Stowell
Parts is expensive, but on the ATC system, I'd be very surprised
if that motor resistor pack wasn't in the speed feedback chain
pretty much as the diags showed.
Stephen Cowell
"Lon Stowell" <Lawn.S...@Komkast.net> wrote in message
With continuously variable speed blower, it's not a simple
resistor pack... more like a speed controller, like the robots
on Robot Wars use. $127 sounds a *lot* more like a
speed controller module than nichrome wire coils and
a thermal fuse. That's what my '93 Taurus LX (POS)
used... now an obsolete part.
__
Steve
.
96JeepOwner
I know this makes no sense, but it is the blower resistor. Yes, I know it
doesn't compute that a bad resister would deliver power to the blower with the
key off and out of the ignition. My 96 Grand had the same issue and I figured
it must be the relay (behind the glovebox on the end of a cable) - but swapped
that out and it made no difference. I presented the problem to the Jeep
Dealership mechanics ( 3 in the shop at the time) and they were stumped -
suggested the 'electrical diagnostic test' at $135 for the first hour. Well,
I bought the $200 Mopar resister and TaDa - everthing works perfectly.
--
for full context, visit http://www.motorsforum.com/jeep/re-help-a-c-blower-motor-won-t-turn-off-9095-.htm
miner_aaron
im have the same problem with a 1994 jeep grand Cherokee limited
--
for full context, visit https://www.motorsforum.com/jeep/help-a-c-blower-motor-won-t-turn-off-9040-.htm