The blower on my '71 no longer comes on at any speed. I kept on hi all the time and used the upper lever to switch the system from Max to Off. I got in the other day and flipped it to Max and the blower would not come on. The next trip, it did come on and has not come on again since I shut it off. The compressor does engage. I have the service manual, but don't know where to begin troubleshooting this. All replies appreciated, its in the high 90's here and this is my daily driver!

First have you checked the fuses?

Including the one under the hood? 71s have a weird set-up.

I checked all the fuses in the underdash block and the inline fuse that is near the hi blower relay. They are ok. I shook the wiring around the relay and unplugged and replugged it with no effect. What next? Thanks.

Do you have power going to and coming from the blower switch?

There's a purple wire that runs up to the high speed relay under the hood. If you apply 12 volts to the purple wire, does the blower motor spin?

I will check the purple wire at lunch today and report back. Dean, I have poor diag skills, so I don't know how to tell if there is power at the blower switch unless someone gives me direct instructions like check the purple wire ;) I can build a car but if something doesn't work, especially electrical, then I have a problem!

Ignition on, a/c switch on, blower switch on, I got nothing from the blower when I applied 12 volts to the purple wire via a test light. I tried the blower switch on all speeds and got nothing. Next step? Thanks!

Ignition on, a/c switch on, blower switch on, I got nothing from the blower when I applied 12 volts to the purple wire via a test light. I tried the blower switch on all speeds and got nothing. Next step? Thanks!

Well, I'll try again. What I meant was give the purple wire 12 volts. That is use a jumper wire, maybe 16 gage or better. Touch one end to the battery (+) and the other end to the purple wire.
The purple wire goes to the motor. The motor should spin. I think it will but that's an easy place to access the wiring to check things.

I clipped the testlight to the pos post on the battery and pierced the purple wire with the end of the light, would that be sufficient to power up the motor?

OK, Dave we'll make this really simple. :p

... That is use a jumper wire, maybe 16 gage or better. Touch one end to the battery (+) and the other end to the purple wire.


No a test light will not cut it. You need to use a larger wire.

This is a professional grade test light, the wire gauge was larger than the purple wire I was testing! I'll try some bulk wire tonight when I get home.

Yeah, but test lights are not made to flow amps, just to check that there is a complete curcuit.

I'll try some bulk wire tonight when I get home.

Cool. That will make a good jumper or link to the battery. Careful not to short the wire to the car body. Might be able to jam the wire up the rear of the connector instead of poking into the purple wire.

I rigged up a few feet of 12 ga wire with a spade on each end, plugged one into the purple wire end and the other to the pos post on the battery. The blower is still dead. What to try next? Thanks. I do have a schematic plus a shop manual but it gives no trouble tree to follow like the newer ones do. I guess it assumes a certain level of knowledge that I lack.

Did you make sure the ground wire had a good connection to the blower housing?

If so, sounds like a bad motor.

Thats kind of what I thought. Looks like the purple wire goes straight to the blower. I can replace the blower this weekend. Thanks for the advice.

Ya know, it's a little strange that the motor just stopped working. Usually they start making some noise before they die.
Just for grins and giggles, might want to check to see if there is power on the purple wire before you pull the motor.
Select heat or AC on the slide levers.
Set the fan speed to HIGH.
Put one lead of the test light on the purple wire.
Connect the other lead of the test light to a known good ground.
The test light should light up if there is power. (12 volts)

Thats what I thought too. All the ones I've had go bad in the past were noisy first. I will check the wire for power when I get home tonight and post back. Thanks.

Now I'm really confused! With the a/c on, high blower on, key on, the test light does not come on at the purple wire. I even pulled the connector loose and checked it at the spade on the hi blower relay that the purple wire fastens to, and no power there either. I doubt that the switch and blower both failed at the same time.

Me too. See anything on the relay control wire? That should be a blue wire. Use your test light to ground with everything selected and the switch to high.

Finally I have power somewhere! With all the switches on, the blue wire lights the test light. It looks like the switch is good maybe the relay and the blower crapped out together?

Blue is the control (coil) wire for the relay.
Blue's power comes from the inside switches so that's a good sign. (Might be no problems under the dash).

If you move the inside speed selector switch from HIGH to MEDIUM, the relay should go "click-click"

Any power on relay orange wire? It should be hot even when the car is off. It comes from the horn relay on the front core support. There's an in-line fuse in this wire. It's hiding inside the plastic gutter on the firewall, behind the distributor. Maybe the fuse popped.

I will try moving the switch and listening for the click. The orange wire has power on both sides of the fuse, I checked it the other day since I replaced it with a newer blade style fuse holder last year when it melted.