Ok, so I am finally able to diagnose a summer time problem that I can now tackle since its, well.. winter time.

My blower motor is not working. It works some times. Other times, it does not. (Blower Motor for the heating/AC)

My wipers work some times, and other times they stop working.

I recently noticed neither works at the same time. Wiper might work and blower does not, then blower does and wiper does not, or both DO NOT work.

There must be something related here.

Ok, so so some background to narrow down all the possibilities. This is a 1979 Corvette L48

My Wiper Delay Module has been replaced.
My Wiper Switch is FINE. I have removed it and cleaned and tested it.
My Wiper Motor is fine.
My Wiper Blades are fine. (Not that that would affect this).
My Wiper Delay Module also WORKS... So when the wipers work, the delay is working, which is pretty damn cool.

As for the AC/Heating.
My Thermostat has been completely replaced.
The Blower Motor is fine.
I've replaced the Blower Motor Relay. (old one was probably fine).
Compressor works.
Heater Core is fine.
I get heat.
I get AC (when the Compressor is able to kick on, when again, the blower motor is working).

When I have this problem I can hear the vacuum pull in the switches as I toggle them for Heat, Vent, AC, etc.

Fuse is ok.

A mechanic friend of mine thought that years of moisture (typical on these Vettes) finding its way down the Windshield pillar down behind the fuse box might have caused corrosion, shorting out?

Anyway, I am at a loss. I have to pull the interior to put in my heat shielding and insulation, so I will have a lot of stuff inside the car apart which should make this easier to work on.

Anyone have any idea why the wipers and the heating/cooling system will periodically NOT work?

Any guidance is appreciated. Thanks.

 

Sounds like nothing more than a bad ground(s). I'm not familiar with that year but I'm sure someone will chime in on where to look.

A bad ground on my '75s wiper system caused all sorts of bizarre problems.

 

That sounds pretty logical given I replaced the delay module. Maybe it is not grounded properly.

 

Well have looked at just about everything and still cannot seem to figure it out.

 

What have you done so far?

 

Checked fuses, checked the wires (3 of them including the purple one) and contact going into firewall and wiper motor. Shorted to wiper motor and tested and it works. Also checked all leads to blower motor for heater and AC which also is NOT functioning. The relay there is new.

 

Usually when this happens it's because the common ground for the blower motor and wiper motor is not grounded near the starter but hooked up to the battery lug. Try running a test jumper from the body of the wiper motor to a ground on the engine.