Chumley

Where would you start to troubleshoot blower motor not working when fan switch is turned on? I thought I would pull the switch first and check it with ohm meter, but once I got contorted and under the dash, I could not get the harness connecter off. Enough energy spent for one day. Is there an easier way to get access (and hand) to the switch that I am not seeing? I can see I will also need magnetic screw holder if I get that far. Chumley

steverw

First I would check the fuse in the fuse box, even if they look good they can be bad. Cheap and easy. If that dosent get it pull the motor and check it, if its never been replaced chances are its bad. There is a high speed blower fuse under the hood. It runs at the top of the firewall/cowl. I think its usually a heavy gauge orange wire with an inline fuse holder, whiteish or black. Switches can go bad, dirty contacts. Try switching it from low to high numerous times to "clean off" the contacts.... maybe.
Some others may have some suggestions too

Steve

Allan R

Chumley, it's not the fan switch. It's the heater resistors that are screwed up. If your car has AC, the resistors are accessible from the engine compartment and are located on the fibreglass casing that runs from the fan to the heater door. If your car is non AC the resistors are located inside the car above the heater plenum chase. Great pic of it in the Cutlass Assembly Manual. Note: different resistors for AC and non AC

AC resistors (this one from Supercars Unlimited)


non AC resistors (this from Inline Tube)

joe_padavano

The very first thing I would do is to apply +12V to the blower motor and see if it spins. If not, either the ground is bad (particularly common for the A/C cars with the non-conductive fiberglass housing) or the motor is bad. If the motor spins, work backward along the wiring diagram.

You DO have a CSM with a wiring diagram, don't you?

Chumley

Thanks for all the input, guys. Yes, I DO have a wiring diagram. I'm familiar with the high speed resistor, replaced one in my Chevy truck, although that affected high speed operation ONLY as I recall. Will check fuse again(last time it looked good) and resistor. Chumley

Allan R

When the resistors on my 72 decided to go, it was the low speed first, then the mid range till all that was left was the high speed. At first I thought it was the switch, but after replacing it and getting the same result, it was easy to pinpoint the resistors. Much easier to work on a non AC car with column shift.

Hope your fix is easy, if you have any of the speeds left it could be the resistors. If you have nothing it could be the fan itself as Joe mentioned. IF it's the fan?? You have a decent sized job ahead because to access it on AC cars you need to remove the RS inner liner to get at it.

Chumley

I discovered that the heat /cool lever has to be slid over to heat/defrost for the switch to work. Don't remember that from 40 years ago with my first Cutlass. Anyway, I have all speeds except high. Is there not just one resistor for high speed only? I thought GM used the same setup on most of its vehicles. This was the case for my 72 Chevy truck. Replaced the high speed resistor and all was good. Anyway, now I can see clearly on those cool mornings, (although its not as much of a problem with summer here) I will pull the high speed resistor and replace it.