I have a '71 442 that is new to me. The wiper switch is set to high and the fan blower motor switch is set to high and all is off. However if you set them to off, then the wipers kick on high and the blower motor runs on high. Exactly the opposite of what should happen, of course. Not sure if related, but maybe it is, the fuel gauge pegs all the way to the right peg. I'm not familiar with GM cars but am trying to learn. I've looked at wiring schematics and have not deciphered a clue. Where do a I start to try and fix this? Any help from someone here would be much appreciated! Thank you.

 

The blower fan and wiper switches are not related.

The wiper switch switches the ground side of the wiper circuit. The GM wipers use a shunt winding that is would opposite of the high speed winding. With the wiper switch on high speed, the high speed winding is energized. On low speed, both the high speed and the shunt windings are energized and the reverse-wound shunt winding negates the strength of the high speed winding to slow the motor. In the off position, the high speed winding is disconnected and the shunt winding remains energized until the blades move to the park position, at which point a cam in the motor opens a set of contacts to turn off the motor. The symptoms you describe could be a bad wiper switch, short in the wires, or a bad motor. None are related to the blower problem.

As for the blower switch, is this an A/C car or not? Does the blower work in the lower speeds?

In both cases, the Chassis Service Manual has the troubleshooting info, especially for the wiper circuit, which is not obvious to most people.

 

Thank you Joe. You are getting me in the right direction, and I am grateful. I've got the blower to where it works as it should except for high. On high, nothing happens. It is a factory A/C car, but the A/C is no longer under hood if that matters.

The wipers are confusing. Off is high, low is low, and high is off. I checked to make sure someone did not install the plug into the back of the switch wrong, and of course it can only press in one way. I would doubt the wires were removed from the plug for any reason, but on a car this old, I guess anything is possible. I will check the Service Manual and keep on going. Thank you.

 

A/C cars use a high speed blower relay that has a separate power supply from the one used for the other speeds. This power is fed by a 30 A fuse that is in line in a wire from the horn relay power stud to the blower motor relay. Check this fuse. If the fuse is good, check the high speed blower relay itself, which is mounted on the firewall.

Make sure the plug on the wiper motor isn't installed backwards. This would have the same effect as installing the plug on the switch backwards. The plug should be installed with the dark blue wire to the passenger side, double yellow in the middle, and light blue to the driver's side.

 

The picture helps a lot. Thank you. Looks like the wiper motor is wired correctly. The plug above is opposite of your picture so I flipped it around and that did not make a difference, but I wasn't expecting it to. The high speed on the blower motor, I think you have got my problem diagnosed. Again, thank you. The wipers has got me stumped.. I'll work my way thru a schematic and sooner or later the problem has to surface. These cars are not that complicated. As mentioned before, I really appreciate your help.

 

Joe has provided good info on blower motor. My 72 has AC and the Hi speed on blower didn’t work. The 30 amp fuse and holder was bad. Found a new one on eBay. A GM New old stock part.


s

This part, probably 50 years old, came with a 30 amp fuse. Getting it apart to check took a little prying! I’m sure it has not been opened since it left the factory.


I bought a new blower relay At Oriley. Was like 15 bucks and they had them in stock. These two parts fixed my blower and it now works all speeds.

I am sure you will figure out the Wiper thing too.

 

On the wiper motor, the yellow wire is power and is hot with the key in the RUN position. The two wire connector is just for the windshield washer, so don't worry about it at the moment. First thing to check is that the motor is properly grounded to the firewall. The motor mounts in three rubber bushings. One of them has a brass strap that runs from the motor body to the screw through the center of the mount. Be sure this is in place. You can temporarily run a jumper from the motor body to a good ground as a test.

Next, pull off the three wire connector (actually two connectors, one with two wires and one with a single wire). Jumper the yellow wire to the center terminal on the motor to provide power (or just run +12V directly to the center terminal). Now ground the terminal on the passenger side. You should get high speed. Now simultaneously ground both the RH and LH terminals. You should get low speed. Finally remove the high speed ground on the passenger side and the wipers should park. If this test works correctly, the wiper motor is good. If not, you need a new motor.