Blower Motor Won't Turn Off

[Fairbs]

I've read other threads, but didn't see a problem quite like mine. I have a 68 Bonny that has decided to have the blower motor on even when the key isn't in the ignition. The dash switch appears to operate the blower correctly on all settings.

This problem is one that I am just getting back to after numerous other more important repairs. I reinstalled a relay. Could it be wired incorrectly and cause this problem?

Thanks for your help.

[randman1]

If you are using a standard automotive relay, it has one lead that we"ll call the input (30) and two outputs (87 and 87a). 87a is a normally closed circuit and the fan would run continously if there is no voltage across the coil. When voltage is present across the coil though, the fan would turn off because the circuit is now interrupted.

You might have the coil contacts connected incorrectly. You will need to verify the polarity from the climate control head. I"m guessing it will be +12 volts. If so, the relay should be wired in this manner:

85... ground
86... fan wire from control head
30... output to fan motor
87... fused +12 volts

Your car is a couple of years older than me so this might be a bit vague for your application. Can you let us know how you have the relay wired now?

[Fairbs]

Originally Posted by randman1

If you are using a standard automotive relay, it has one lead that we"ll call the input (30) and two outputs (87 and 87a). 87a is a normally closed circuit and the fan would run continously if there is no voltage across the coil. When voltage is present across the coil though, the fan would turn off because the circuit is now interrupted.

You might have the coil contacts connected incorrectly. You will need to verify the polarity from the climate control head. I"m guessing it will be +12 volts. If so, the relay should be wired in this manner:

85... ground
86... fan wire from control head
30... output to fan motor
87... fused +12 volts

Your car is a couple of years older than me so this might be a bit vague for your application. Can you let us know how you have the relay wired now?

I've dug into the blower motor circuit a bit more and have found that there are two relays involved. Each relay has three contacts (case grounded I believe).

The blower is connected to the left terminal of the relay 1. The left relay 1 terminal is also connected to one of the resistor block terminals. The far right terminal of relay 1 is connected to the resistor block as well as the left terminal of relay 2 and also continues toward the inside of the car (three wires come together and continue inside).

The right terminal of relay 2 is connected to the alternator. The middle connector of both relays go toward the inside of the car on separate wires. I believe these are the control inputs.

There are also two other wires that lead from the resistor block to the inside of the car.

I guess my next step is to see whether the relays are working. How do you go about testing them? Also does anyone know what the specific relays should be (like part #)? I checked the one relay wiring against a salvage yard car and the color coding matched up. The other relay has a connector block so I don't think that one could be wrong.

Thanks for the help so far. -Andy.

[randman1]

Depending on how you are looking at the relay, your description can mean several things. Look for a pin configuration like this:
and the terminals labled with the numbers. Note the different direction that some of the pins are oriented. This will help in determining the pins if they happen to not be numbered. This is a standard automotive relay and is a generic part. There are some relays within vehicles that are application specific and therefore have a GM part number. I would think that your relay(s) are of the generic type though. Link to relay basics

If your relay(s) do not resemble the above, can you snap a pic for us?