'67 heater blower electrical question

[Larry S.]

About all I know about electricity is to turn on the wall switch and hope for the best. I successfully replaced my heater blower motor with a new one from LI Corvette, but it still won't blow. Acorrding to my handy-dandy little circuit light, I have power to the motor. When I turn the fan switch on, there is a faint popping noise through the radio speakers and the courtesy lights dim ever so slightly.

Bad ground? Bad motor? I'm not impressed with the ground connection at the motor flange since it is mounted on a painted area, but that's the way the old motor was, too. Any tricks other than the obvious use of an alternative ground and power source? Thank you.

[Gary P.]

Re: '67 heater blower electrical question

Take a wire from the battery (Hot side) and put it on the motors terminal, if it works its not the motor. check the end of the wire with a light to see if you have power.

[Larry S.]

Re: '67 heater blower electrical question

Greg, I did that, and the motor works. But, it doesn't work when I connect the wire from the fan switch, although my test light says there's power at the connector. Clean the connector, clean the ground, or what? Thanks.

[Larry S.]

Re: '67 heater blower electrical question

Greg, I cleaned the connector, and here's what happened: I turned the fan on low and got nothing, then on medium and got nothing, but high speed worked. I tried again and got low and medium speeds but no high speed. Several repetitions got low and medium speeds but no high speed. Any suggestions?

[Joe R.]

Re: '67 heater blower electrical question

Greg, I cleaned the connector, and here's what happened: I turned the fan on low and got nothing, then on medium and got nothing, but high speed worked. I tried again and got low and medium speeds but no high speed. Several repetitions got low and medium speeds but no high speed. Any suggestions?

Hi Larry:

The speed control for the motor applies 12V through one resistor for low speed, 12V through another resistor for medium speed, and applies 12V directly to the motor for high speed. So, it sounds as though you have some bad connections, possibly in the dash switch.

Just to try the easy stuff first, try cleaning the contacts on the connector to the resistors. The resistors are open-air wire coils that are mounted in the air stream of the blower for cooling. On my A/C car the resistor assembly is mounted on top of the evaporator box in the engine compartment. It is held in place with two screws.

It is common for the connector on the resistor assembly to get hot enough to melt and deform, and the electrical contacts can be affected by this.

Since you say that even high speed doesn't work sometimes, I don't think the problem can be exclusively blamed on the resistor assembly. For high speed, the resistors are bypassed. I'm not 100% sure how the bypass is achieved in a non-A/C car, but I believe that in an A/C car the bypass is somehow mixed in with the A/C relay. I can't recall whether your car has A/C or not.

Anyway, I hope the above info helps you at least a little bit. There is always the chance that the switch in the dash is bad, but hopefully the problem is somehow related to parts that are more accessible.

[John H.]

Re: '67 heater blower electrical question

Larry -

If your car has A/C, the feed to the blower for high speed is through a relay, fed by a red wire from the horn relay; that red wire has an in-line fuseholder - open it and check the fuse.

[Larry S.]

Re: '67 heater blower electrical question

Thanks, John. Where might that red wire and fuse be located? The high speed did come on once when I first tried it, but that may have blown the fuse. If I weren't so darn hard-headed, I'd have paid a mechanic to put the blower motor in (I hate standing on my head to work on something!), but it's done now--a job I don't want to repeat.

[Joe R.]

Re: '67 heater blower electrical question

Hi Larry:

The "big red wire" is visible in the attached photo. It runs down the driver's side fender to the horn relay. The white, in-line fuse holder is visible in the photo. I'm not certain, but I think the fuse rating is supposed to be 30 amps.