[AElayyat]

Im my 85 FWB w/ 4100 the heater is not working the way it should. I replaced the heater water valve (the one located by the trans. dip stick) with no success. The temp door is operating the way it should be.

If I set the temp to 80 or 90 the cabin will get warm, but when I turn the fan on (set at the above temps) the air is not warm. Could this be a heater core problem or am I looking at something else?

Any help is always appreciated guys. Thanks in advance.

 

[sizanjdf]

sounds like the door that opens to let fresh air in isnt closing like its supposed to when u turn the fan on. probably an easy fix if u can find the motor that opens and closes it.

 

[Katshot]

Check your heater hoses. They should both be HOT, not warm, but HOT. If they aren't:
1. If both are cool or only warm, most likely cause is a bad thermostat.
2. If one is hot, and one is only warm, most likely cause would be a clogged heater core.
You should also make sure the coolant is up to the proper level since this too, can have an affect on the heat.

 

[AElayyat]

Those sound like very good suggestions, I will check into both of them and report back. Thanks for the help guys.

 

[N0DIH]

Cadillacs for some reason seem to have a higher than usual heater core plugging problem than other GM cars that I have owned. But then again, all my cars I have owned and maintained since low miles, and the Cads were much older. Likely just lack of maintenance. I typically backflush my cars once a year with the Prestone kit. And refill with distilled water!!!