Strange Audio Tone from HVAC Control Unit Area
 

Have a 2000 GM LS with 83K miles. Driving today and after a few miles I started to get an intermittent, but constant, audio tone coming from around the digital HVAC control panel. They has never happened before. The tone is not mechanical.

I though it was the radio. No. Then my cell phone, no. I turned off the HVAC control and the tone stopped. Turned it back on and it started a few miles later. Turned it off and the tone stopped. Kept it off and the tone started again-- even with the HVAC controls in the off position. All heat, AC, vent, temperature adjustment and outside temp controls work as the should.

Just for kicks, I stopped by my dealer and asked them. They had no clue-- other than the HVAC control module was going bad.

Does anyone have any idea what's going on.

I had a very similar problem with my MGM as well. It turned out that one of the vacuum control motors that control the vents in the HVAC system had gone bad, and was leaking vacuum every now and again. It sounded very much like an alarm or electronic noise at the time, and it took me a while to pin point it. I basically disassembled the center portion of my dash, and then had an assistant drive the car while I listened inside with a small piece of hose. Once I found the vacuum control motor, I put my hand on it and felt it vibrating to the same frequency as the audio tone. I replaced the vacuum motor, and never had any trouble with it since.

I made up some instructions on how I replaced the vacuum motor, send me an email if you want me to forward to you.

Thanx Freedom . . . it was a vacuum motor $29 dealer part and four hours labor to install.

Replace Idle Air Control Valve
 

How difficult is it to replace the idle air control valve on a 2000 MGM?
Is the valve located at the rear of the air intake?

A very simple repair. The only thing that could possibly go wrong would be overtightening or cross threading a bolt, other than that everything is exposed and easy to reach.

is it this problem?

http://www.youtube.com/watch?v=i9FsrPrGqXI

My grand marquis beeps, stops when i turn off the air controls or turn down the heat under 22 degrees but sometimes still beeps and i have to keep playing with the air controls tilll it stops.

Hello yurigrandmarquis,

Yes that is the same exact noise that my car made, when one of my vacuum controlled actuators began to fail. The actuator is located inside your dash, behind the climate control unit. There are actually three actuators located inside the dash, used to control the HVAC vents. One of the actuators (the one that is most likely to be causing trouble) is a bidirectional, (moves air into one of two possible chutes) while the other two actuators are simply open or closed. I think that the bidirectional actuator is more prone to failure due to the fact that its armature must travel (to cover both chutes) and that is why this problem is so common. I replaced mine with one that I got from a police car in the wrecking yard, and I've not had any problem since then. I will try to post a picture of the actuator, or if you send me an email upal_2@yahoo.com, I will send you a picture of it.

Picture of vacuum actuator
 

Here is a picture of the actuator that failed within my MGM, and caused the same noise as within the above youtube video. The actuator that failed, is the one with both the yellow and red vacuum lines attached to it.

Picture of vacuum actuator
 

Here is a picture of the vacuum actuator removed from my car, and sitting on work bench. Note the two 1/4-20 studs located on diaphragm housing. These nuts are a little tricky to get to with open end wrench, but you can do it if you are patient. Like I always say, if you're not sure what you're doing, go out to the wrecking yard and perform surgery on a car similar to yours. BTW, this thing is approximately located behind the climate control and ash tray assembly.

Hey thanks a ton, I'll probably just get a mechanic to do it because I don't feel like messing around with cars but ya just no mechanics i talked to not even the ones at ford could tell me what the sound was. Thanks and happy holidays