Questions and Answers

Plymouth Acclaim Heater Q. Hi, If I am understanding this correctly you will answer questions that I have about fixing my car. I have an 1989 Plymouth Acclaim with a 2.5 liter engine and air conditioning. My problem is I get no heat from my heat setting. The blower motor works fine but no heat will come out. I have tried back washing the coolant in the system to see if the heater core is plugged but that did nothing.

I tried forcing the water both ways and it flows quite rapidly both ways and doesn't appear as though it is clogged anywhere. Also the water is totally clean once the coolant is flushed out. I also tried a "GUNK" 10 minute system flush but it did not help. Funny thing though, when I was running the car for the 10 minutes while the chemical was in the system, I would turn my heat on an just for a few seconds it would blow nice warm air and then immediately turn cool again.

Other than that I can think of nothing. A friend suggested maybe the thermostat was stuck open and not allowing the water to heat properly but I would still get slightly warm air if this happened wouldn't I? Let me know if you can think of anything.

Thanks,
Dean

A. Both heater hoses should be HOT to the touch (coolant return hose should be slightly cooler than the supply hose). Now, first thing to do is to see if you have vacuum at the heater control valve when the lever is in the HOT position. If there is no vacuum, then you have a problem with the heater control panel or vacuum supply.

If you do have vacuum, then it's probably a bad heater control valve. If you supply vacuum from a hand vacuum pump and there is no change in hose temperatures, then the heater control valve is bad. You can take it out and look inside to see if it opens and closes.

If the heater control valve is fine, then you probably have a clogged heater core. The construction of a heater core is such that if it is 95% clogged, water will still pass through the remaining 5% and come out clean.

If everything checks out fine, then you have to look inside the heating vents for an obstruction.