2000 bonneville hvac

You have to remove the lower dash trim to access the area in question. First check for a loose vacuum hose on one of the vacuum control motors.

Do you have sufficient air flow out the dash vents, floor, & defroster vent when the selector lever ( buttons ) are set?

If you do there may be a another reason why you are always getting warm air - the dreaded loss of refrigerant.

You may be able to peak inside the firewall area and see if the AC Evaporator Core is plugged with dirt & leaves. You can remove the blower resistor to see inside.

Good Luck.

========= Harryface =========

1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~283,383 miles_~_~_

~_~_~_~_U.S.A._~_~_~_~_~_

~~~The Former Fleet ~~~

89 Cavalier Z 24 convertible 78 Holiday 88 coupe 68 LeSabre convertible 73 Impala sedan

Thanks, harryface.

I did all that but no luck. It just seems like the heat never shuts completely off. I think they just use a damper door to regulate the air across the heater core. The AC comes on OK but is warmed by the heater and when the heat is 'off' it is never all the way off. I removed the lower plastic and unscrewed the heat control door from the mount. I can hold the door closed manually and still get warmed air. I think the door seals poorly or has a 'bypass' hole in it. I could put a water control valve in the line (I don't think this vehicle has one) but it just irks me that there is not a solution to the factory engineering deficiency.

This doesn't sound like an engineering deficiency, it sounds like a malfunction inside your heater box. You could install a heater control valve like you suggested, but the proper way to fix this issue (provided your diagnosis is correct) is to remove the heater box, take it apart, and find and repair the specific problem inside. This is enough work that you will want to make specially sure you original diagnosis that the air is being warmed by the heater is correct.

had a similar problem with my 99 Grand Am.

My Heater Control knob turned a potentiometer hooked electrically to a motor that follows the Heater Control position and opens and closes the heater door. Pot became "noisy" (or dirty inside) and would not control the door. Door hung open about half way, heater was on half way all the time. Turning Heater Control full CCW or CW sometimes resulted in heater OFF or ON full blast. If your Heater Control knob is mounted to the shaft of a small square block (3/8" x 3/8") with 4 contacts, and the entire block (potentiometer) is mounted on a PC board with transistors and at least one IC your set up is the same as mine.

To clean the pot put 1 or 2 drops of pot contact cleaner on the pot by the 4 contacts (cleaner is available at Radio Shack). I took the cheap way out and used 91% Isopropyl Alcohol.

Larry

hyundaitech wrote: