AC Blower Issues

[uhhair]

So I pretty much have all the electrical gremlins from our car fixed except for one: the AC blower. Currently, it only works on speeds 2 and 3. All the relays have been replaced, as well as circuit breakers, fuses, ect. Fairly sure it is a bad switch but I am wondering if anyone has had similar trouble and maybe has an easy way to 100% diagnose the problem. I don't want to buy a new switch if I'm not certain that is the issue. Thanks!

[thegovernor9912]

replace the transistor inside the blower motor. Speeds one and two run thru this. Its near where the power wires attach to the blower motor. I would clean all the wires with contact cleaner as well.

The switch is not expensive and its easy to replace if you have any doubts about it. Again I would at least try and clean the contacts inside.

[DMCMW Dave]

replace the transistor inside the blower motor.

?????

You can feed power directly to the resistor bridge at the blower and see if you get all 4 speeds there, but based on the symptom it's the switch.

Speeds 1 and 2 run from the switch and are fused, 3 and 4 are on relays and are on a breaker. It's common to lose 3 and 4 or 1 and 2, but not 1 and 4. If the resistor fails you generally lose 1, 1 and 2, or 1,2, and 3 but never 4.

[Bitsyncmaster]

Speeds 3 and 4 run the power off the blower circuit breaker. Do you read voltage on both sides of that breaker (the 30 amp breaker)?