1974 Big block with air conditioning - fan problem

[Gary C.]

[Tom B.]

Re: 1974 Big block with air conditioning - fan problem

Is there a high blower in line fuse holder in the circuit somewhere? A lot of GM cars used a high blower in line fuse holder.

[Paul B.]

Re: 1974 Big block with air conditioning - fan problem

...I'm nowhere near an electrical engineer, but I've chased down a fair amount of shorts & electrical issues. Have had a '74 Corvette for 31yrs, but it's a non A/C car. Been looking at my '74 GM Service Manual for about a half hour and didn't see an inline fuse for "high" speed. Wondering if it's the switch itself that is bad?

[Mark E.]

Re: 1974 Big block with air conditioning - fan problem

For 1970, there's an in-line fuse in the wire from the horn relay battery terminal to the blower relay. It's typically a couple of inches from the horn relay. This circuit is dedicated to the high-speed setting so that's a common culprit if high speed doesn't work. I don't know if 1974 has this or not.

You might also check the blower relay and the blower resistor.

[Edward J.]

Re: 1974 Big block with air conditioning - fan problem

Gary, the blue wire coming from fan switch is the signal wire to high blower relay. Take your multi meter and see if there is a connection there when you turn on high speed. Also I have also seen the orange wire heat up so bad that the plastic gets hot and melts, and the connector does not make a connection at the relay, try turning fan on high speed and wiggle the orange wire at relay and see if the blower turn on.

[Gary C.]

Re: 1974 Big block with air conditioning - fan problem

I found this drawing on the another forum. Looks like the high speed position goes through two switches.Capture.jpg

[Colin M.]

Re: 1974 Big block with air conditioning - fan problem

Yes there is. It has a 30Amp fuse and goes to the blower relay. It checks out OK

[Edward J.]

Re: 1974 Big block with air conditioning - fan problem

Your drawing shows the switch on high speed, it looks like orange on the drawing turns on the high speed relay. Not sure about the diagrams wire color?