Hit-or-Miss Heating
J.B. Wood
unusual heating behavior: With the passenger compartment temperature
set at 85F I only get cold air coming out of any of the ducts even when
the engine temp is nominal (mid range on the temp gauge). The weird
thing is that after I drive the car to work and it sits outside all day
I always have loads of heat available when driving home. The coolant
level is where it should be and the water pump and thermostat were
recently replaced. Does anyone have an idea? Thanks for your time and
comment. Sincerely,
--
John Wood (Code 5550) e-mail: wo...@itd.nrl.navy.mil
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337
m6onz5a
> Hello, all. My 1990 Mercury Sable has lately been displaying some
> unusual heating behavior: With the passenger compartment temperature
> set at 85F I only get cold air coming out of any of the ducts even when
> the engine temp is nominal (mid range on the temp gauge). The weird
> thing is that after I drive the car to work and it sits outside all day
> I always have loads of heat available when driving home. The coolant
> level is where it should be and the water pump and thermostat were
> recently replaced. Does anyone have an idea? Thanks for your time and
> comment. Sincerely,
> --
>
> Naval Research Laboratory
> 4555 Overlook Avenue, SW
> Washington, DC 20375-5337
maybe a sticking heater/exchange box unit
hls
"J.B. Wood" <john...@nrl.navy.mil> wrote in message
news:hg59bg$52u$1...@ra.nrl.navy.mil...
> Hello, all. My 1990 Mercury Sable has lately been displaying some
> unusual heating behavior: With the passenger compartment temperature
> set at 85F I only get cold air coming out of any of the ducts even when
> the engine temp is nominal (mid range on the temp gauge). The weird
> thing is that after I drive the car to work and it sits outside all day
> I always have loads of heat available when driving home. The coolant
> level is where it should be and the water pump and thermostat were
> recently replaced. Does anyone have an idea? Thanks for your time and
> comment. Sincerely,
Was it like this before you had the thermostat replaced?
J.B. Wood
Hello, and thank you and others for the quick response. I had drafted
my OP up last week and while it was true I've since stopped getting
heat going home as well. A couple observations:
1. I'm not sure if the '90 Sable has a heater core flow control valve.
Even if it does and it's intermittent would that explain:
2. There have been several isolated instances where the temperature
indicator (engine has been running for a while) has gone to its maximum
value and just as quickly dropped down below below the midpoint before
returning to the midpoint. My conclusion here would be low coolant but
the coolant appears to be full. I'm speculating that something is
restricting coolant flow such as a partially-blocked radiator or
somewhere else other than the heater core but before the thermostat.
Any further insights are most welcome. Sincerely,
jim
You could have air in the system. That could have happened when the
thermostat was changed. I didn't see where you gave an answer to the
question in the post you are responding to:
"Was it like this before you had the thermostat replaced?"
-jim
Tim Wescott
> Hello, all. My 1990 Mercury Sable has lately been displaying some
> unusual heating behavior: With the passenger compartment temperature
> set at 85F I only get cold air coming out of any of the ducts even when
> the engine temp is nominal (mid range on the temp gauge). The weird
> thing is that after I drive the car to work and it sits outside all day
> I always have loads of heat available when driving home. The coolant
> level is where it should be and the water pump and thermostat were
> recently replaced. Does anyone have an idea? Thanks for your time and
> comment. Sincerely,
Your shiny new thermostat is a piece of s***?
Just a stab in the dark; whenever I replace something and things get
worse it always seems to be one of three things: I broke something else
during the 'fix', I put in a faulty part, or what I fixed overstressed
some part of the system that was on the hairy edge, and it broke.
hls
"Tim Wescott" <t...@seemywebsite.com> wrote in message
news:RfmdnX6b3-kJHrvW...@web-ster.com...
Some thermostats can be put in upside down, I seem to remember.
Also some GM variants had special side flow thermostats or some such,
and even though they might fit similar cars, they did not work
interchangeably.
I dont think Ford went this route, but if the problem came on after he
changed
the thermostat, air in the system, or a thermostat malfunction is certainly
to
be looked at.
I have worked on older Fords that I had to take a hose and blow the crap
out of the heater core and make sure the heater valve was working. Havent
worked on a Sable or Taurus however.
dsi1
I don't think there's any problem with coolant flow through the heater
core. I'll bet your problem is the blend door in the heater box. I don't
know how you would check/repair something like that.
dsi1
> 2. There have been several isolated instances where the temperature
> indicator (engine has been running for a while) has gone to its maximum
> value and just as quickly dropped down below below the midpoint before
> returning to the midpoint. My conclusion here would be low coolant but
> the coolant appears to be full. I'm speculating that something is
> restricting coolant flow such as a partially-blocked radiator or
> somewhere else other than the heater core but before the thermostat. Any
> further insights are most welcome. Sincerely,
>
You should verify that your coolant level is OK and there's no leaks. If
that's the case, change your thermostat. I think that your heater
problem is unrelated to your coolant problem.
hls
"dsi1" <ds...@humuhumunukunukuapuapa.org> wrote in message news:jKxVm.46756
> I don't think there's any problem with coolant flow through the heater
> core. I'll bet your problem is the blend door in the heater box. I don't
> know how you would check/repair something like that.
I dont know about Sable. On some cars you can get to them well enough
to manually operate the doors. If they are vacuum operated, you have
another burden to bear.
If the doors are stuck, you can sometimes free up the mechanical pivots
of the blend doors with a little shot of aerosol lubricant.
A Sable mechanic would likely know all the systems.
I dont understand why this system would work in the afternoons, but not in
the mornings,and now wont work at all. I am sure it will make sense once
he gets into it
Really helps to have a good manual when you are trying to DIY something
like this.
Steve B.
>Hello, all. My 1990 Mercury Sable has lately been displaying some
>unusual heating behavior: With the passenger compartment temperature
>set at 85F I only get cold air coming out of any of the ducts even when
>the engine temp is nominal (mid range on the temp gauge). The weird
>thing is that after I drive the car to work and it sits outside all day
>I always have loads of heat available when driving home. The coolant
>level is where it should be and the water pump and thermostat were
>recently replaced. Does anyone have an idea? Thanks for your time and
>comment. Sincerely,
First thing to do is make sure the engine temp really is up where it
needs to be. I don't think this is your problem but it is an easy
place to start. Also check your heater hoses and make sure both of
them are hot. Two hot hoses tells you there is coolant circulating
through the heater core.
You said you set the temp to 85 which tells me the car has an
automatic climate control system and I think this is probably where
your problem actually is. Most common is a blend door that is
sticking. When that door doesn't move the air isn't directed through
the heater core so... no heat. It could also be a problem with the
temperature sensors not knowing the temp of the car or just a general
fault with the automatic system.
If you aren't used to working under the dash and you don't have arms
with five elbows I would probably find someone that does a lot of this
type work
Steve B.
dsi1
>
> "dsi1" <ds...@humuhumunukunukuapuapa.org> wrote in message news:jKxVm.46756
>> I don't think there's any problem with coolant flow through the heater
>> core. I'll bet your problem is the blend door in the heater box. I
>> don't know how you would check/repair something like that.
>
> I dont know about Sable. On some cars you can get to them well enough to
> manually operate the doors. If they are vacuum operated, you have
> another burden to bear.
I don't know anything about these systems because in the past, if it
went bad, I'd just run without the heater. The idea of working under the
dash is pretty unappealing - thank God I live in the tropics. My guess
is that the Ford uses vac servos to operate the doors and one could do
an initial check with a hand held vacuum pump. I'll bet the system tends
to leak when the rubber hoses are cold.
hls
"dsi1" <ds...@humuhumunukunukuapuapa.org> wrote in message news:d5AVm.80866
>
> I don't know anything about these systems because in the past, if it went
> bad, I'd just run without the heater. The idea of working under the dash
> is pretty unappealing - thank God I live in the tropics. My guess is that
> the Ford uses vac servos to operate the doors and one could do an initial
> check with a hand held vacuum pump. I'll bet the system tends to leak when
> the rubber hoses are cold.
There are different systems and you really have to know what you are doing.
Some GM systems, for example, us a vacuum modulator module that is a little
difficult to diagnose without the proper tools,and is DAMNED expensive to
replace. This system operates blend doors, etc.
Sables and Tearasses are just something I dont know anything about, and
really dont want to learn.
I wish it were as simple as it used to be, with just a manual linkage to the
blend doors, a simple valve, etc. But it isnt always that way.
mvh
Jack Myers
It certainly sounds like an air bubble. Just to be sure, are you checking
the coolant level in the cooling system itself rather than in the
overflow tank? Wait until the engine is dead cold and then remove the
remove the pressure cap. Top it up. After the initial fill you need to
"burp" it--run it through a full temperature cycle with the heater on--
then top it up again. After that you can leave the cooling system
sealed and simply watch the fill lines on the overflow tank.
then "burp" it. h
--
Jack Myers / Westminster, California, USA
An expert is a person who has made all the mistakes that can be made in a very narrow field..
- Niels Bohr
dsi1
> dsi1<ds...@humuhumunukunukuapuapa.org> wrote:
>
>
>> On 12/14/2009 6:51 AM, J.B. Wood wrote:
>
>>> 2. There have been several isolated instances where the temperature
>>> indicator (engine has been running for a while) has gone to its maximum
>>> value and just as quickly dropped down below below the midpoint before
>>> returning to the midpoint. My conclusion here would be low coolant but
>>> the coolant appears to be full. I'm speculating that something is
>>> restricting coolant flow such as a partially-blocked radiator or
>>> somewhere else other than the heater core but before the thermostat. Any
>>> further insights are most welcome. Sincerely,
>>>
>
>> You should verify that your coolant level is OK and there's no leaks. If
>> that's the case, change your thermostat. I think that your heater
>> problem is unrelated to your coolant problem.
>
> It certainly sounds like an air bubble. Just to be sure, are you checking
> the coolant level in the cooling system itself rather than in the
> overflow tank? Wait until the engine is dead cold and then remove the
> remove the pressure cap. Top it up. After the initial fill you need to
> "burp" it--run it through a full temperature cycle with the heater on--
> then top it up again. After that you can leave the cooling system
> sealed and simply watch the fill lines on the overflow tank.
>
> then "burp" it. h
It's surprisingly tricky to fill radiators these days because they tend
to be lower than the top of the engine. On my Taurus, I can tell if it's
full by squeezing the top radiator hose. The first time I changed the
coolant in the car, I loosened the clap on the hose that went to the top
of the engine. Now days I don't bother - I'll just run it through
several heating a cooling cycles and purge air bubbles by squeezing the
hose.
m6onz5a
> unusual heating behavior: With the passenger compartment temperature
> set at 85F I only get cold air coming out of any of the ducts even when
> the engine temp is nominal (mid range on the temp gauge). The weird
> thing is that after I drive the car to work and it sits outside all day
> I always have loads of heat available when driving home. The coolant
> level is where it should be and the water pump and thermostat were
> recently replaced. Does anyone have an idea? Thanks for your time and
> comment. Sincerely,
> --
>
> Naval Research Laboratory
> 4555 Overlook Avenue, SW
> Washington, DC 20375-5337
I just read a couple of TSB's on the blend door having issues with the
cable etc.. It also mentioned something to the effect if you are
having a problem with the blend door turn the key off and back on and
see if it works then.
Mark
I had a heat problem in a Taursu casued by a clogged heater core.
There is a bypass hose right across the input to output of the core
located on the firewall so just becasue you have flow through the
heater core hoses doesn't mean the flow is actually going through the
core, if the core is clogged, the flow will go through the bypass
hose.
I carfully pinched the bypass hose with vise grips to force flow
through the core and back flused the core. that fixed it for me....
YMMV.
Mark
ben91932
> Hello, all. My 1990 Mercury Sable has lately been displaying some
> unusual heating behavior: With the passenger compartment temperature
> set at 85F I only get cold air coming out of any of the ducts even when
> the engine temp is nominal (mid range on the temp gauge). The weird
> thing is that after I drive the car to work and it sits outside all day
> I always have loads of heat available when driving home.
There is an in car temp sensor behind the glove box and a sun temp
sensor under the left side of the dash.
If there is no air in the system, I'd take a look at those.
HTH,
Ben