My blower motor runs in only 1 mode; Full Blast. Positions 1-3 appear to be dead but it position 4 the motor runs at full speed.

Questions; What would cause this? Dash switch? A relay somewhere? All wiring is in place and motor sounds fine, not sticking or making odd noises. Nothing is blocking the blower motor and is turning free by hand.

Thoughts?

 

Sounds like a bad blower motor resistor..

 

Try cleaning connections at the resistor. Mine has been finicky, I finally replaced it, works great now!

Pat

 

Make sure your temperature setting its on max cold or heat, it it is you will get full fan, if you move it off slightly you should have all speeds.

 

I mis typed, if it is on max cold or hot, you fan will be high.

 

Your '68 does not set the fan to High when the Temp. lever is all the way one way or another, so that leaves the resistor and the wiring associated with it.

If you have A/C, it's on the evaporator box under the hood.
If you have heat-only, it's under the dash behind the glove compartment.

- Eric

 

Mine is a '71 and it has (well HAD) A/C. Same place?

 

Yes. Exactly the same.

- Eric

 

Just a thought-I've had two instances in the past where the culprit was actually corrosion between the relay, its fasteners, and the firewall-on some vehicles the ground for the relay is actually the mechanical mounting point between the relay and firewall. I had a '70s era GM car that had an intermittent blower speed problem. I bought a new high blower relay, and as I was preparing to remove the old one, I noticed its mounting bolts were a little loose. I had the key on at this point, and the blower was selected to "high" but was not running. As soon as I put a socket on one of the relay bolts and turned it a bit, I saw rusty dust falling out from under the relay flange from the bolt threads. A second later the blower started running. I removed both bolts and cleaned them with a wire brush, as well as the back of the relay mount flanges and its corresponding mounting area on the firewall, bolted it back together, and it worked like a charm. I'm not saying that's your problem, but it's an easy enough thing to check on any car, and the repair cost is zero.

 

Just to clarify, if the relay had a bad ground, Chris would be having the opposite problem, and have no High speed.

That still leaves (in addition to the resistor) the connection between the relay and the resistor as a possible trouble source, and the remote chance that the relay could be stuck in the On position.

- Eric

 

Thanks gents. I will dig into it and report back.

 

Look at heat-AC fuse. That's the one feeds the control head and low-speed resistors. High speed runs off its own fuse and wiring.

 

True, but that can't be his problem, because the Heat / A/C fuse also feeds the power to pull in the High speed relay and put the fan on High speed (unless his High speed relay is also stuck closed, which is unlikely).

- Eric