QuestionAFTER REPLACING BOTH THERMOSTAT AND HEATER CORE, I STILL AM NOT GETTING HEAT. I THINK I CHECKED ALL VACUM LINES. BLOWER WORKS,A C WORKS, BUT TEMP CONTROL DOES'T SEEM TO CHANGE TEMP. CONTROL WAS FINE PRE HEATER CORE REPLACEMENT. WHERE COULD MY PROBLEM BE.
AnswerHello Michael,
On your next question, it would help me if you can give some information such as year, make, model, engine, etc. as well as any work you have done concerning the problem,(Which you did fine here).
Depending on the vehicle, you may not have any type of coolant control valve to the heater core, and coolant runs through it all the time.
I expect you know by now if coolant is flowing through your heater core, and will assume it is.
Next is air flow in the heater box.
Again, vehicle dependent.
But in most GM vehicles, all the air is directed through the air conditioner evaporator all the time.
Then, beyond that, there is an airflow control door that either directs the air through the heater core, or around it....or a mixture of both, depending on the temp selector position.
Then there is a third door that directs air to the defroster.
Here's the rub....
Older vehicles used cable controlled doors that the operator actually moved as desired.
Then came vacuum, or vacuum/cable mixed, where some of the functions were selected by a rotory knob, and it controlled vacuum to vacuum motors on the doors.
Later comes electronic controls to vacuum control solenoid valves, and the doors still operated by vacuum.
And another form of control is full electronic, where the controller is all electronic, and it operates little electric "stepper" motors that operate the doors.
So type of vehicle is imperative.
Here is a little link you might find useful.
I don't especially buy many parts from AutoZone, but their website, www.autozone.com allows you to fill in your vehicle information, and then for most vehicles, they have complete service and repair manual access. All free.
Also troubleshooting techniques.
Van
