New Thermostat, Still No Heat

[kcac]

Got a new thermostat, so the engine is running warmer now - around 160 - 180 degrees, which is odd because it was a 195 degree thermostat.

 

Anyway, the car is a 95 Cutlass, 3.4 L with the electronic climate control. When I set the temperature for the warmest setting, the air coming out of the heater is unheated. It only gets slightly warm if the car sits and idles up to around 200 degrees.

 

Has anyone dealt with symptoms like this before? My guess would be a clogged heater core because it does put out a litte heat, but only when the car gets around the 200 degree mark.

 

I'm going to look at the actuators that control the temperature doors for the heater core tomorrow. I just want to see if they are moving, at all, and if they are in the right position. On the other hand I can't see it being the heater core doors, because how would that explain the slight amount of heat when the engine gets around the 200 degree mark? If the doors are stuck closed, no heat should get through. .

 

If this sounds like something you've come across, please let me know what you did to fix it.

 

Thanks in advance for any ideas on this.

[Slade901]

Is your cruise control working?

 

Cruise control and the cold/hot air vent selector switch is usually controlled by the same vacuum for both cruise control and cold/hot air vent selector.

[musthavemuzk]

when you replaced the t-stat did you bleed the air from the system?

if airlocked this could cause no or minimal heat.

 

slade has another fair option. you could have bumped a vacuum line loose when you were changing the t-stat. this is a common thing

 

Monty

[Brian P]

I think it could be your climate controller. If you want to you could pull off the little motor that operates the heat output control "door" and open it up fully by hand. It isn't too hard but you'll need to be up under the dash. Let me know if this interests you.

 

EDIT: I just reread the bottom of your post. It's a possibility that either the controller won't command the motor to move to the extreme, or the motor physically can't do it even though it's trying.

[kcac]

System was bled, although I guess I should take another look to be sure, and recheck the vacuum lines just in case.

 

Brian is probably on track with his guesses it's either the controller or the motors. I can't see two electric motors going out at the same time, but I'm praying it's not the controller - it's a $500 part.

[Brian P]

2 electric motors? What year/model vehicle?

[kcac]

It's a 1995 cutlass with the automatic climate control unit that has separate controls for the driver and passenger. There are two doors for the heater core, one is controlled by the driver, the other by the passenger. Or the driver can elect to just control both.

 

I've got a service manual, and it shows (and states) just both motors, no vacuum. Vacuum is used on actuators that direct the air to the different outlets.

 

The manual outlines a trouble shooting sequence using a digital volt ohm meter at the connectors for the two motors. I'm hoping it's either the motors or air in the system. That controller is expensive $$$.

[god910]

Yeah, motor should control heat, the vacuum controls the mode doors. This exact problem is why God created zip ties.

[DiscoStudd]

Before you spend 5 Bills on a new HVAC control, take it apart and re-solder the pins on the main IC chip. I did this to the HVAC control from my old LeSabre when it was acting goofy. The controller worked beautifully right up until I traded the car (about 2 1/2 years afterward.) An electronics tech friend of mine told me that sometimes the small wires inside the IC chip break contact with the pins on the outside, and usually a little bit of heat on those pins will melt the wire back onto the pin. He was right, BTW...

[Brian P]

well...I can locate a digital controller if that is your prob. But I didnt realize you had a '95. The controller shouldnt be at fault but anything's possible. The heater core or lines going to the heater core could be built up and/or blocked with crud. Noone converted that car to dexcool, did they?

[kcac]

Brian

 

Yea DexCool was in the car when I bought it. I have no idea how long it was in there, or if they flushed the system before adding the DexCool.

 

I changed it back to the green stuff {ethylene-glycol). Thanks for the offer to locate on the controller

 

That's the thing with used cars, you never know what the person before you did or did not do..

[Brian P]

I'm in your boat trust me. I bought my '95 thinking that the coolant was just really old green stuff (resevoir was brown) but when I drained the coolant it was all orange, it was like 100% coolant too, no water added. And of course I got the typical "Dexcool is eating my damn intake gaskets" sludge on the radiator cap. I was so pissed. I did a flush, running water thru the radiator and thru the engine till it was all clear, then refilled with green within an hour of owning the car. I had only asked you about whether or not your car was converted to dexcool because there's an increased possibility that you have heavy amounts of sludge in the heater core and lines. I've seen this happen on occasion where I work.

[93CutlassSupreme]

if all else fails, and you really need heat, just get a few cans of baked beans, and a box of matches

[91oldscutlass]

My Cutlass has no heat. There was a clicking sound coming from under the dash. Driving me crazy I pulled the cover off the bottom of the dash and was following where the noise was coming from. There inside the heater box was the noise. Theres a plug...I think 4 pin deal... I disconnected it and the noise stopped. So did the heat. So whatever is in there controls the heat. Maybe this is your problem. You may not have had the noise I had... but this is a possibility of your heat problem.

[kcac]

Is there a chemical flush that clears out the sludge? I did remove the right dash insulator to take a look at the heater door motors. I guess based on what 91oldscutlass is saying, I need to confirm whether those doors are working in order to confirm whether the core is plugged.

 

Didn't go any further than remving the dash insulator because to see more I would have had to take apart the ductwork and didn't feel like getting into that.

 

I looked up the procedure (below) for changing the core. IF it is the core, what a pain this is going to be.

 

Remove/Disconnect

 

Air cleaner and duct assembly.

Drain coolant.

Upper intake manifold.

Fuel lines.

Upper radiator hose at engine.

Exhaust crossover pipe.

Transmission dipstick tube.

Both heater hoses at heater core.

Right and left instrument panel sound insulators.

Rear compartment heat duct adapter bolt/screw and adapter.

Heater outlet duct bolts and duct.

Heater core cover.

Heater core.

[Brian P]

Wholly Hannah! That's definetly the 3.4L instructions. Eek. Well if you want to do a quick test without removing more under-dash panels than the outermost one, locate and unbolt 1 of those control motors (should just be 2 7mm bolts) and twist the little pin thats attached to the heater door (which the motor grabs) and see if heat suddenly comes out thru the vents full force (with the vent on of course) that's what I'd do personally.