perl200

Hey guys. In about the last month, I noticed that I have a buzz that has started either in one of the relays on the firewall or behind the dash. (my 1990 200TQ) I wonder if anyone has had this happen before. My first thought was that what I was hearing was the fuel pump taking a dump, but I was able to verify that it is coming from the front of the car. Do I have a relay or some module that is planning on dying? Any thoughts on this?

Thanks,

Paul

Will Ng

See if the buzz is coming from the middle of the dash, specifically, the lower temp sensor for the climate control. There is an annoying little fan that can be a noisy and irritating PITA as it gets worn. Usually loud when the temperature is below freezing.

perl200

I'm thinking that it is coming from close to the center of the dash, and it is really noisy when it gets real cold outside.

I didn't realize that there was even a little fan for that sensor...

I'll investigate further.

Thanks,

Paul

CARSNPLANES

When I did my heater core, and had the blower box out of under the dash, I decided to look at my noisy sensor fan too. It was something that squealed, buzzed etc. It certainly was annoying. I was searching for a new one but since i had room to work under there with the climate box out(it's almost impossible to get to it with everything in place)I decided to remove it and see what's what.
After removing the assy from the dash underside, the motor and fan/sensor sits in a shell that can be split. What I've found is the motor sits suspended in the shell halves between foam pads. The fan, being attached to the motor, being very exact in the it's opening, has through the years "drooped" as the foam compresses and drops a little allowing the fan to rub the bottom of the opening. Think of the fan as a radiator fan in it's fan shroud and the engine mounts have dropped allowing the fan tips to rub the bottom of the shroud.
I placed a more denser foam in there to "raise" the motor on the high side allowing for a slight drop eventually from gravity. I checked the brushes and blew all the brush dust out and reassembled evrything.
Nice and quite now! No more banging on the dash. All that did was change the "pitch" of the squeal!!
Hope that helps.

boxerfan

So that's what that noise is... thanks.

perl200

I can hear this humming when the climate control is off or on, it makes no difference. This morning I did an experiment. When I fired my car up for the first time today, I just turned the ignition on but didn't start the car. I did notice a really faint humming coming from the dash, (the small fan I think?) then I started the car and I could hear the loud hum. I don't know for sure but I think it might be something else. It does sound like an electrical hum for sure. Maybe like a pump, but I can't think of a pump mounted on the firewall?

Thanks,

CARSNPLANES

The fan is on all the time. There is just little voltage with just the ign on. Start the car, more voltage =louder.