1992 Cadillac STS Heater blows warm air out passenger side

TSHAWNW

MEMBER
1992 CADILLAC STS
V8
FWD
AUTOMATIC
132,000 MILES

No trouble codes but I have a list of problems that could be related. When it is VERY cold out (0 or less), my cooling fans for the radiator will kick on. However, if it is above 0, the fans never turn on and the car will almost overheat on hot days. Heater blows fairly warm air out the passenger side but ice cold out the drivers side. Cooling system has been flushed and flows well, All vacuum hoses are hooked up. It is almost like there is a door in the heating part that is staying open causing the cold air to come in. AC works so-so in the summer but takes awhile to cool down. No complaints there though. Thermostat works, engine reaches running temps. I'm a fairly gifted mechanic but am clueless here. Spent 900$ last winter trying to get this problem fixed and the GM dealership said they had no clue and passed over a bill to me. Please help. It's -10 here.

1 Reply

JASONRAY

MECHANIC
213 POSTS

Is the DEFROST on? That uses the A/C compressor automatically. That could explain the fans coming on.
It sounds, though, like maybe the control head is at fault. That's what controls each door. Does it have Dual Climate Control? If so, there's 2 doors in the evap. Case. 1 for the driver's side and one for the passenger side. One could be opening partially(kinda warm air on Pass. Side) and the other could not be at all(ice cold on Driver's side) Since we're having trouble with both, I'd blame the control head. I'd have a hard time thinking BOTH door actuators went bad at the same time. Be sure to check ALL fuses. A single fuse may control both so check 'em all. Repost and let me know what you come up with.