Cadillac Heat 1990 Seville
 

I notice if I start my 1990 Seville with the heat on, or start the car and turn the heat on right away, I get a really loud, nasty sound. From outside the car, the sound is louder. The first time it happened, it sounded like the air mix vent was a little sticky. Times afterwords, it sounds like a rogue elephant is running through my dash. Can anybody tell me exactly what this is, and is it possible to spray some silicone on the actuator door (if that is what it is? and where is it located?) I had heard somebody else have a similar problem in another forum. I also talked to a cadillac guy and he said this was a common thing.

I notice when I turn the heat on after the car has warmed up or run for a minute or so, it does not produce this sound. Why is that?

I don't believe my heater core is plugged up, but can someone assure me that these cars just don't produce heat like the new cars? It gets warm, but it doesn't get HOT.

so it creeks a little.... its old enough......lol....... is the sound coming from under dash, or in the engine compartment?..... does the heater work properly?.... ac?
rickyd

It may be old, but only has 55,000 miles. That's what happens when you buy a car to replace your old one and don't expect an AMC to last another 7 years.

The A/C works fine. The heater works fine.

Because the sound is louder from outside the car, I presume it is coming from the engine compartment nearest the firewall, driver's side. If it were under the dash I would imagine the sound to be as loud as if I were standing outside the car when it made it.

It is not a creek. It is a loud, scary sound. My only concern is that if I do not remedy this, something is going to break.

id try to pinpoint from where under the hood is the sound is coming.... could it be a belt?
let us know
rickyd

The blower bearings going bad?


.

It's not a belt. If the blower bearings were going, I'd imagine that I'd hear the noise more or less continuously. I only hear the noise when the heater is first turned on immediately after a cold start, or performing a cold start when I had left the heat running when I last shut down. The sound only lasts about 3 seconds and is in conjunction with the sound of a vent door opening, but I can not imagine a vent door alone making this kind of a noise. Once again, only seems to be happening on cold starts.

Is it possible that a sticking vent door could make the electric motor that opens it strain very hard? That would make sense to me, but I am not familiar with what the actuator motor looks like/functions. Is the vent door run by vacuum or electric motor?

Doesn't quite sound like a gear stripping, but more like an electric motor making a growl. From outside the car, was loud enough to make a friend of mine go "WHAT WAS THAT" from about 20 yards away.

*Update: Let me add so far it only does this when the heater is on and set to AUTO. I haven't tried other settings. I understand that the compressor runs in this mode (or at least when the defrost is on), however, the compressor and clutch check out fine. No noise when turning A/C on. It's not the vent door opening, I can hear that and seems fine. It's not the blower fan, it turns on. Just after it turns on, then something else turns on, RPMs drop a tad and then the noise. What other device can be running? I looked under the dash and in the center console area I found a 3 or 4 wire connector disconnected. I will investigate that this weekend. Not sure if that has anything to do with it.
I also noticed that if I set the temp to 90 degrees, then bring it to 60 and let the A/C come on, then bring it back to 90 degrees, the sound happens again. Not as loud. After 2 or 3 times doing this, the sound doesn't happen again.

How about the water valve?