I located this unit under the dash, passenger side of my 72 Maverick 4 door. It was unplugged and when partially plugged in, the unit vibrates and buzzes. I am trying to get my interior fan switch to operate the different speeds again but came across this. Also, if anyone has a recommendation on what to check for my fan speed selector not working anymore, that would be great. It just stopped working one day a couple years ago. I replaced the red resistor on the blower housing and that didn’t fix it.
Part number search indicates it's the buzzer for the seat belt and ignition key. It was probably intentionally unplugged. That's one of the first things I did on my '73 when I got it many years ago.
There is some air flow through the vents/defroster but does not change with speed selector switch on dash.
Oooh, save that, it's rare! Mostly because everyone hated that buzzer so much one of the first things they did was find it and get rid of it.
If you're in a boneyard, pluck one out of a newer car that has the chime tones instead of the buzzer. They swap right in, same plug.
Most commonly, when the fan speed doesn't change, it is due to a defective resistor. These are usually a plug in module under the dash not far from the fan. They're often attached to the back of the heater box. Haven't ever replaced one in a Mav so I'm going by other cars.
I replaced my resistor a few years ago when I had similar issue as CalifMaverick. I did have hi-speed only -- fan worked on hi-speed. Replacing resistor solved my issue. CaliMav. replaced his resistor -- didn't solve his problem. Maybe the motor is bad?
It doesn't sound like your fan is working at all. You should be able to hear it/feel it when it is working and turned on. I bet it is the fuse.
If fuse is bad, most likely, has a short circuit or motor drawing to much current. If replacement, blows a 2nd fuse, that is where I would concentrate my research efforts.
Agreed, if resistor is bad, HIGH will still operate. High bypasses resistor, lower speeds have a voltage/current drop through resistor.