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I drove my car this morning and I have no heat at all. The heater valve is newer and looks perfect, any advice on where to start searching. Coolant level is fine and air in the system should not be an issue, since the system has not been opened in a year or so.
Ok, just messed with it a bit. I disconnected the valve under the hood and no differnce. Checked the defrost and no difference. I disconnected the rod at the box after trying to adjust the heat with no change. Once I disconnected the arm on the box on the driver side and pulled the arm manually, I got heat.
I assume this could be the servo on that arm or the head unit. How do I check the head unit and or servo?
First of all we miss having you around here. I hope you are enjoying the Az son.
I believe this door has a servo, at least that is what it looks like. I don't think it is vacuum operated, although I could be wrong as this is my first time messing with anything on the hvac system at all.
Do you have any thoughts on how to test it? I have already checked clark's garage and there is no info. on there for lack of heat.
When switch 1 is pressed, the outside-air openings are closed and conversion is made to air- circulation.
When switch 2 is pressed, irrespective of the sliding switch position (4 and 5), the footwell flap is closed and the defrost flap opened. At the same time, the heater is turned all the way up, the outside air blower switched to level 4, and the A/C compressor switched on.
The outside air switch 3 has 5 positions. In position 0, the outside air blower starts upon ignition at the lowest speed.
Slide switch 4
Left stop - defrost flap closed
Right stop - defrost flap open
Slide switch 5
Left stop - footwell flap closed
Right stop - footwell flap open
Temperature setting switch 6
Left stop - maximum cooling
Right stop - maximum heating
When switch 7 is pressed, the A/C compressor is switched on.
That should give you some places to start checking for proper operation. They don't offer up any further info on the climate control system for diag purposes. If you find they are electric servos, then check for power etc, also make sure all the linkages are hooked up, as the clips on the back of the climate control head are known to break. At least they are only like $3
Hey Doug,
I have checked the operation of all the above mentioned items. Everything works perfectly with the exception of the heat. When I hit the defrost button the vents close, the ac turns on, and the fan turns up, but no heat. Every other item is working as well.
The clip is fine, I actually disconnected it to get the heat on, however the servo or what ever type of actuator is not moving. I will try a multimeter and see if the servo is bad.
The heater control valve is vacuum operated, I know you said it's new-ish, but make sure the valve lever moves when vacuum is removed, and then reapplied, also make sure there is vacuum present when you unhook it with the car running.
If your clip is good, and your valve is opening with hot water flowing into the heater box, the only thing left is the blend door/actuator or the linkage to the climate control head. There isn't anything else in the system really
Does anyone know a test procedure for the unit or servo? I find it strange that I can not make the servo do anything at all.
Yes! If you pull the connector to the servo motor, you will see six pins. If you apply 12V to pin 4 and 5, the motor should move in one direction. If you reverse the polarity, the motor should move in the opposite direction. If that works, then your climate control unit is probably faulty.
I had this no heat issue four times over the last 25 years and three times it was a faulty interior temperature control sensor.
Part 944 624 013 00.
Once it was the main dash control unit.
01-08-2015, 10:37 AM
No heat.
