This Florida summer is brutally hot. Just retired and I'd like to drive my 68 GTX around.
Here is the problems.... Turn on AC and it will blow cold air from 15 to 45 seconds. One time out of ten it won't blow at all.
Ran power directly to blower motor and it will run all day.
Is there a resistor somewhere that controls fan speed on AC cars?
Where will I find it and is it fixable or replaceable.
If replacement is needed who can supply one?
Does the dash switch just turn things on and off or is there magic inside?
THANKS for any and all help.

There is a blower motor resistor, and the switch, although not magical often burns up on inside.

Yours being that it works when first turned on, I hate to just take a guess on it, but I believe it's probably the switch.

I'd suggest to look in the factory service manuals at mymopar.com for guidance or just disassemble and get a visual.

Zippy may be right as I believe the resistors are only used for low and medium speeds. if that is the case it would point to the switch.

I had to find a used resistor for my 69 GTX. The wires going into it were melted so it was obvious what I was facing. I jumped the motor first and then went looking at the harness when I knew I had a good blower. The resistor is easy to get to, it’s basically above the gas pedal and is inside the air box held in with two small screws. The wires in a plug with 3-4 going into the top side and a single at the bottom.

I was under the impression high speed was full 12 volts. Once I got the new(used) resistor in and repaired the wires, I found out it is not that way. This is my first old mopar with working ac. You can do a relay so as to boost things up to their full potential. I found max ac doesn’t have enough fan power for me, but using regular ac is acceptable. Someday I’ll get around to doing the relay, but for now it’s on to other needs when I have garage time.

I got my resistor from Tommy White at Parts Hound in WI. I agree that you should look at your switch unless you find a melted mess like I did.

Here’s a reference pic I took of the wires before I busted the melted connector off.