dkdj98

My '95 Suburban is starting to have a few electrical issues. Most I have been able to resolve, but this one I am not sure of. The rear blower motor would come and go for several months. No one hardly ever rides with me so I didn't worry about it. It has now quit completely, so I decided to go ahead and check it out. I assumed it was a grounding issue. I pulled the rear panel to get access to the blower motor and I ran a new ground wire and nothing. So then I ran a wire from the battery to the blower motor just to put 12 volts on the motor and see if it would spin up and it spun up just as it should. So I got my DMM out and checked the voltage going to the motor. In the off position, the voltage is zero, which is to be expected. On low, medium and high settings, the voltage is around 2.5V. I then pulled the resistor, and I didn't see any issues with it. I put a volt meter on each of the inputs to the resistor and back to the motor ground and again, I just had about 2.5V. I checked the 50A fuse under the hood and it was good, I pulled the relay an put it back in, but I don't have a good way to check to see if it's good, but I'm not sure that a relay would cause a drop in voltage like that. Any ideas of where to go from here?

in2pro

Actually the relay could cause the drop, if the contact inside the relay has a lot of carbon or arc build up it can cause a very poor connection....
See if you can walk it with another one in the under hood fuse block, be sure to mark it so you don't get it mixed up....

dkdj98

Thanks for the quick response. I'll check that out and let you know if that works.

73shark

Did you check the input voltage to the relay contacts? The input and output to the contacts (not the coil) should be nearly the same except for a very minor drop across the contact.

You could also jumper across the contacts and then check at the motor to confirm or rule out the relay.

Typically the relay is only in the circuit on High due to the higher current. If that's the case, then you should have 12V at the input to the resistor and a lower voltage at each of the output legs as the different resistor values step-down the voltage for the different speeds.

dkdj98

OK, So the relay I pulled earlier was not the relay for the Rear Blower Motor. And I'm not able to find the relay for the rear blower motor. I've found several Fuses controlling the rear AC, but no relay anywhere. I have a spot under the hood in that fuse box for Aux Fan, but it is not pinned out and there is no relay there. There is also a relay hanging off the side of the box which is not labeled on the map of the lid of the fuse box, but I disconnected it and I'm still getting the 2.5V to the motor. Can someone direct me where to find the relay that controls the rear motor? I've spent about an hour researching online and I've looked everywhere but I can't seem to find it.