: Heat blows only after engaging compressor

02-21-05, 04:14 AM
Hey all, I searched the forums but didn't see anything enough like my situation, so here I am. I have an '89 Brougham that I just picked up from a local car dealer we know and trust. The car is nearly flawless.


I can drive for 20 minutes or more, set at 80 degrees, and the heat won't blow from the lower vent. I have to turn on either the A/C or the defroster (thereby engaging the compressor) and wait for the fan to spin up. Once the fan is going, I can switch it back to heating and the air will blow from the lower vent. Even pressing "HI" doesn't cause the fan to blow until I've engaged the compressor. After that, everything works fine, until I turn off the car and come back to it later.

I read about all these vacuum hoses and stuff...could that be part of the problem? I know he paid his mechanic to work on some vacuum hose responsible for setting the temperature correctly...any connection that you can see?

I appreciate any information or suggestions anyone might have. I've been a member here for about a year and have saved myself a lot of trouble (and money) by following others' advice. Thanks in advance.

By the way: anyone interested in an '83 Seville in good condition? Heh.

02-21-05, 04:01 PM
This is a climate control system, not a heater and an air condtioner. Setting the temp to say 75 degrees and engaging AUTO will allow the system to work as designed. interior colder than 75? heater comes on after a short delay to allow engine to warm up, then heats interior to 75. Interior hotter than 75? then cold air conditioned air comes from the dash almost immediatly. The reason for compressor engagement almost all the time is to de- humidify the air entering the interior so as to not fog up the glass. If ECON is used then the system is less efficient but will attempt to warm or cool the interior as best it can. In ECON the fan seems to stay on high longer because its less efficient. This system will NOT allow heater air from the dash vents. Some people dont like this but thats how its designed. One other thing, if the engine is running too cool then the blower will delay longer on cold start. Verify engine temp. should run 195 to 220.

02-21-05, 11:51 PM
Thank you for your reply, however, I am aware of what you've said. I think the nature of my problem was not made clear in my first post.

Example: The car's interior is 65 degrees. The engine is warm enough to produce adequate heat, take my word for it. The "Climate Control System" is set to 75 degrees (or even 90), on "Auto." Heat does not issue forth from the heating vent. It trickles in, is definitely warm or hot, but does not "blow" at the capacity of which it is capable.

If I lower the temperature setting to 60 degrees the fan engages and blows cold outside or air-conditioned air from the appropriate vents. Similarly, if I depress "HI" while at the coldest setting (or anywhere below the actual interior temperature) the fan will engage. Pressing the "Defrost" button forces air to blow through its appropriate vents. I can even adjust the temperature upwards at that point, if I so desire, and the defrost vents will blow out WARM air, with heat blowing from the lower, heating vent as well. THEN I press "Auto", with a temperature setting of, say, 75 degrees (when the car's interior is still below that) and warm air will blow from the heating vent, below the dash board. The air will continue to flow until the cabin reaches 75 degrees. Once I have followed this procedure the "System" will function normally. I can press "HI" or "LOW" and warm or hot air will blow from the heating vent at the specified speed. (Incidentally, warm air will blow through the dash vents if set to "Econ," depending on how high you set the temperature. Air of up to 75 degrees seems to come from the dash vents when set on that mode.)

So, to sum up: in order for the fan to blow heat when the interior is cold and the engine is warm, I must first engage the compressor, then switch to "Auto" (or "Econ") and allow the system to do its blessed job of making me happy, warm and fuzzy. :halo: Hopefully this clarifies the issue I'm having.

02-22-05, 12:52 PM
It sounds like your Climate Control system mode doors or the control unit itself is acting up. There's very little vacuum lines in these cars compared to my old 1968, and from reading, it appears that when "tricked" the control unit is activating the proper mode doors, etc. The fact that you can trick it into blowing hot air through the bottom vents seems to tell me that lines are ok and that the control unit is having a difficult time figuring out what to do until you thwack it on the head :want: by adjusting the temp setting.