View Full Version : Cold heat in my 91 Brougham

02-03-09, 08:38 PM
So it was really cold today, about 20 degrees. The inside of my car never would get warm, it was maybe 50-60 degrees in there.

I had the temp set on 90, econ. There was air coming out of the lower vents like it should, although it was kind of cold. Definetly a lot warmer than the outside air, but probably 50-60 degrees. The fan kept running on high, so the auto-climate knew it wasn't the right temp, it was trying to warm the car up by dumping maximum heat.

This is a new problem, the heat has worked great all winter long. I have a few theories.

1. Thermostat stuck open, so the engine isn't heating up.
2. Plugged heater core(can you flush it, or do you replace it?)
3. Flapper/damper under the dash is stuck and isn't letting air pass by the heater core.

02-03-09, 08:55 PM
I pick #1. I just dealt with the EXACT same thing in my Roadmaster. Ten bucks, and about ten minutes to change. If nothing changes, then flush the heater core.

02-03-09, 10:21 PM
The Econ setting doesn't turn on the heat; it only turns on a fan in the vent. Try AUTO and see if you still have a problem.

02-03-09, 10:27 PM
The Econ setting doesn't turn on the heat; it only turns on a fan in the vent. Try AUTO and see if you still have a problem.

I've gotten pretty good heat using the econ setting. I thought the difference between the econ and Auto setting is that Auto will always run the a/c compressor, while econ shuts it off. The temp display is what determines the damper on the heater core.

02-03-09, 11:30 PM
AUTO will only run the AC compressor when it's warm out or when you are using the window defrosters (and the engine is cold). I believe ECON also opens the vents to the outside air, where AUTO recirculates the air from the cabin, but I'm not sure.

My car used to have a vacuum leak in the climate control circuit, and I could drive all day in ECON with out a problem, but if I used AUTO and tried to accelerate, the air would stop coming through the dash vents, and start coming through the floor heater vent. So I'm sure ECON is venting from outside air that comes through the engine bay.

02-04-09, 12:08 AM
Aron9000 is correct. Econ simply keeps the computer from providing a ground to the A/C compressor to complete the circuit and turn it on. The compressor engages in auto to provide drier air regardless of temperature set by the driver. In the winter auto mode keeps the windows from fogging up by providing dry warm air. The system is designed to be in the auto mode 98% of the time all year long. The temperature of the air entering the car is determined by the climate control module comparing inside vs. outside air and adjusting the interior temperature to what the driver has set on the dash display. Yes, replace the thermostat first. Should be a 195 degree one. If still not warm enough, remove the glove box and watch the blend door rod move from max cold (60 degrees displayed) to max heat (90 degrees displayed) with car running of course. This rod should move slowly and smoothly thru its entire travel. If it is jerky or stops at all, the climate module is faulty.One thing to check before anything else is the level of coolant in the radiator. If low, the heater will be lousy. Pressure test to find the cause of the low fluid. The only time I use econ is when the sunroof or any window is open. No use trying to cool or warm the entire earth.

02-04-09, 11:03 PM
guys , does the heat only come out of the floor and windshield vents , and not the middle vents , I have a 90 fleet brougham , not sure if this is normal , my heat takes a long time as well

02-04-09, 11:45 PM
Yes, this is a climate control system, not a heater and air conditioner like a Chevy. New owners of Cadillacs, for some reason, want to operate the system rather than setting it somewhere around 72 to 75 degrees and leaving it alone in auto year round. The system will give less problems left alone. I rarely change the temp setting on my Cads.(maybe 5 degrees at the most) I will switch to low if outside temp is comfortable or if I open a window. Letting the system gently raise or lower the blower speed and move the blend door in regards to the in car temp sensor will prolong the parts of the system. The whole point of owning this type of car is to have the headlights come on when needed automatically, the parking brake to release simply by moving the gear shift, and the climate to adjust itself all year round. Thats the meaning of luxury, very little driver involvement. A slow to warm heater is most likely a wrong thermostat (180 instead of the 195) or a thermostat that doesn't fully close when cold.

02-05-09, 12:22 AM

02-05-09, 12:43 AM
The reason I run it in econ is to keep the a/c compressor off when I don't need it. Improves gas mileage, and the inside windows fogging isn't a big deal if you keep them clean.

02-05-09, 09:32 PM
According to my OEM Cadillac factory Service Manual, "When the ambient temperature is above 32 F, the compressor operates to ensure dehumidification of the air even though it is not required for cooling." Beyond that there is no mention of compressor operation during heating.

You live in Nashville, and think 20 F is "really cold," so there may be nothing wrong with you cooling system. ECON works great around the freezing point, but may not be able to function below that. I would not begin to change parts until you did a performance test on another cold day using AUTO.

02-06-09, 01:12 AM
I'm going to change out the thermostat tomorrow and report back. Although its supposed to be 60 degrees all weekend, might have to crack open the sunroof:D