heater blower motor not working - 86 Monte Carlo with LS Swap

[paradigm]

I have an '86 Monte SS with an LS swap. The prior owner removed the A/C and installed a heat only system. When I turn on the heater fan, nothing kicks on.

Where should I be checking for the actual blower motor, the relay and any fuses? Any other common connections to check for?

 

[86 Salon]

Do you have power and ground at the motor?

 

[paradigm]

I checked the 25A fuse in the A/C location and it looks fine. Is there a different fuse to check?
Also where is the heater relay located?

Would terminal B on the below photo be the positive lead, and terminal A be the ground lead? Would the resistor be behind C?

Do you have power and ground at the motor?

I am not sure where to check that - is that at terminal A and B shown in the above photo?

 

[86 Salon]

I checked the 25A fuse in the A/C location and it looks fine. Is there a different fuse to check?
Also where is the heater relay located?

Would terminal B on the below photo be the positive lead, and terminal A be the ground lead? Would the resistor be behind C?

I am not sure where to check that - is that at terminal A and B shown in the above photo?

Yes, connect a test light between power A and ground B. IIRC, there is no blower relay on a non AC car, but there is one on an AC car. Maybe the previous owner just removed the AC and installed a non AC control. If that's the case, you would need to do some rewiring. If you don't have power at the blower motor, see if you have power to the orange wire at the fan switch. If you have power at the switch, you would need to connect that wire to the blower resistor. You should get a factory service manual. It's a simple system, but there are differences between a non AC and an AC car. I'm going by my 1986 Cutlass manual. A MC may be different.

 

[paradigm]

There is 12V at the orange wire leading into the switch. Is the brown wire at the top of the switch harness ground? It wouldn't serve as ground when I tried to check the orange wire against it.

The heater resistor seems badly corroded, I will replace it. I put 12V straight from the battery to the blower motor positive lead, and there was nothing. The housing of the motor is corroded so I am not sure if it was getting ground.

I am going to replace the blower motor too; I am hoping I could get it with a new housing to eliminate any rust issue. The heater box has some sort of old foam between that and the blower motor housing - what should I use there to reseal the blower motor housing?

 

[86 Salon]

Make sure that you have a good clean ground on the motor. Even if you get a new motor, you'll still need to clean the ground at the motor. That ground, according to my 86 Olds manual, is grounded at the right lower instrument panel. Pull the ground off of the terminal at the blower motor. Then remove the terminal on the motor and sand it clean. If the terminal looks bad, replace it. Don't replace anything until you diagnose it. Remember, the Chinese replacement parts will probably fail after a short period of time. Your resistor looks pretty rusty, but it doesn't mean that it's bad and even if it is, you would still have high speed.

 

[paradigm]

Would you happen to know what this black wire is attached in series with the orange power wire leading to the blower motor? Looks like a resistor?

 

[ELCAM]

That's a feed through capacitor to keep the motor brush noise out of the 12V power supply.

GM # 3906187 and other numbers.