1996 Deville

[DHO]

When I got Appa (96 Deville), barely anything worked on her, and month after month I have been very fortunate in diagnosing and fixing her problems. I am no mechanic, but i love my car and want her to work like a Cadillac should. My next project is the heater, and it's a real head-scratcher. Here's what is happening....

First of all, My heater is not blowing hot air at all

Also, with the heater setting on, it will not blow out of the main vents and only scarcely blow out of the defrost and foot vents, while on the cold setting it will blow out of the front vents at full blast.

I have changed out the thermostat ( which was nonexistent). I was sure that would fix my problem, but it seems as if it is a little bit more complicated than that.

I checked my fuses

My radiator fluid is good.

I got no clue what to do for my next step, any advice would be much appreciated

[Cadillac Jim]

First, you should run your on-board diagnostics (OBD) trouble codes, list them, and post them here. That will tell us what is causing any messages or turning on any warning lights and possibly much more, and will point the way toward repairs. To run the OBD codes, turn on the key and, on the A/C console, press <Off> and <Pass Warmer> together for a few seconds until all the dash lights come on like you just turned on the key, then release them. The message display will show the codes, one at a time. When they are done, you will get the prompt "PCM?" at which time you turn off the key. Write them down and post them here.

There are several things that can be causing the no-heat condition. The heater hose or heater core can be blocked or clogged, the HVAC controller can have a bad connection or a bad vacuum hose, or one or more of the mixer doors or their vacuum-operated actuators can be sticking. Problems with the HVAC controller or mixer doors will throw an OBD code.

You can do a quick check of whether vacuum is getting through the HVAC controller by starting the engine, pressing the emergency brake, and then shifting out of Park into Reverse. If the emergency brake doesn't automatically disengage, the vacuum line is disconnected or kinked somewhere between where it goes through the firewall on the passenger side, through the HAVAC controller, and then to the emergency brake release.

[joeb]

No thermostat is almost always a sign of overheating issues. What else would it signify? Thank ur stars ur car is not overheating after installing thermostat.