heater help please

[G Winter]

I have an 89 Riviera with a heater problem. One day I couldn't control the heat , couldn't turn it off. The following day the heat was gone. Air cond. works. I checked under the hood and all vacuum lines seem to be intact.I really don't want to dig into the dash without some info on it.
I hope that someone can give me some info on this system or point me to a place with information on it.

Thank you
Glenn

[JohnZ]

The GM factory shop manual would probably be the best place to start - they go into LOTS of detail on heating & A/C systems.

[G Winter]

I really don't care to buy a manual for an 17 yr old car with 230k + on it.
I am not sure how much longer the car will live. I did some more checking on it
directs airflow correctly to dash vents , defrost and heater ducts.This says it isn't a central vacuum problem.. I can't find a water control anywhere under the hood. I am a little afraid it is in the temp control unit,which might be a cumputer in itself because this car does have the onscreen controls.
Thanks for responding though.

Glenn

[gmjunkie]

I had a 90 Buick Lesabre Limited do the same thing!! It wound up being a electronic control module under the hood about the middle of the cowl on top of A/C heater case,it was held in the case with 2 or 3 screws and had a gang of wires plugged in to it! (8-9) My cost was about $75 at the Buick Store!!It controlled the door for the heater core and a/c evaporator!! It don't have a water valve, it moved the door to mix hot air with cold to get the temp for the Climate Control!! It also dose other functions too, like speed up and slow down fan!! Mine started out like yours is doing but finely it got so the fan would run all the time,even with the ignition off!! Hope this helps!!

junk!!

[G Winter]

That sounds like really good info. I actually have a junk Riv the same yr setting out at my brothers farm. Have harvested about $800 worth of parts off of it in 4 yrs. Now if I can locate it on my car I should be in good shape.
Thanks a bunch junk
Those of us that drive junk need lots of help.

Glenn

[G Winter]

I just went out and checked. There is something attatched into the top of the heater box with two plugs in it. One is a heavy gauge red and the other has 3 or 4 wires. I suspect this might be the fan speed control resistor. The only other thing I found was a huge mass of wires going into the firewall on the passanger side. I am afraid what you talked about may be under the dash.
I will check it out some more after work tomorrow.

Glenn