The blower motor is inop on my 77 w/AC. The fuse is good, as is the blower resistor. I checked voltage to the relay and I have power to the left wire on the two wire connector. (The wire looks brown to me but the wiring diagram calls it pink). On the three wire connector I have power to the red and dk blue wires. No power to the purple, which looks a little melted. Which wires do I jump to check the relay?

 

I would check the ground first.

Ron

 

The relay only comes into play oh hi speed.

 

There are some simple tests you can start with to try to narrow this down.

First and foremost, I always like to test the motor. It take only a few minutes and takes it out of the picture or places it in the picture instantly.

I would disconnect the power wire from the blower motor. (Leave the ground on it) and then run a 12 volt jumper to the blower terminal... Make sure the blower is working. If it fails to run, I would then run a second jumper for ground on the motor and test with positive again.

You state you have power on the blue wire but not on the purple. Are you positive because you should have power there if the switch is in the second position? The relay is just a basic switching device. Pull the relay from the car, and pry off the top, you can do this by un-bending the fingers that hold it. It won’t hurt anything. Inspect the contact points top and bottom.. Clean, file the points and make sure if you file them to file them flat when closed. The contacts should not burned.

Then with a voltage tester, power up the relay with a ground and see if it switches.. if it fails toss it and replace.

The two wire side of the relay is what actually makes it switch so you can put power and ground here and the relay should switch. The connector is pictured below



Notice the orange wire... this is what makes the relay pop for the high speed. When people have no high speed, usually this is the first place they should check for an issue. But as 75 stated, this only comes into play when you are in high blow position. When in High the relay pops.. switches the power supply to the red wire instead of the dark blue. All power feeds on the dark blue are based on which position you have the speed switch in... from the resistor.

So using the picture of the relay below as a reference.

2 and 101 are your power feeds to the blower motor through 65. 65 should have continuity between itself and 101 at all times if the motor is not in high speed.

150 and 52 are your electro magnet power and ground.

65 is your "Out" power wire to the blower motor.

So..
With power on high speed (orange) the relay, 65 should be feed power by 2
With power on any other speed, 65 should be feed power by 101.

Make sense?? I hope so.. heck I'm getting lost.

 

Great, that's just the info I need. One more Q though, where is the blower motor ground located?

 

Ground is attached to one of the screws that holds the fan against the firewall, the other end should be attached to the frame.

Ron