Hello all, I"m trying to find a wiring diagram for the Dealer AC fan switch.

Usually, it's a few wires going to the blower and resistors.....But Nooooooooo.
This thing has 2 big honking relays, that are molded TOGETHER as one unit, a big honkin' harness and a microswitch.

The dealer AC side works excellent on all fan speeds. Turn it off, the Underhood blower works on med and low...no high. Apply power to the fan(12V direct batt.) it spins right to high. I'm assuming the problem is in that relay pack/thing/PITA as the fan switch makes the inside blower work on all 3 speeds.

Anyone have a diagram for the Dealer Air?

 

Today's update.

Blower now works on low and high....but only if blower is grounded to the frame.....but ground wire in the harness to motor sees cont. to ground

Cont. through the resistor on the proper terminals.

fan switch sees proper cont. on all positions.

The problem HAS to be in that relay-pack thing.

Any thoughts from anyone?

 

My 1981 EVTM doesn't say a thing about dealer-added A/C of which there were at least two different variants, sorry.

From what I remember...

The microswitch determines which blower motor is being used at any given time.

The dual-relay pack, no idea there. In general, Ford controls and throttles the *ground side* of the circuits; for example, the factory blower resistor pack offers high resistance to ground on low speed, not so much resistance on medium speed, and no resistance on high speed.

We used to have a guy here named Ralph (81-F-150-Explorer) IIRC he described the dealer-added setup several (3-4-5+?) years ago... it'd be in the archives but finding it would be the problem... you might have luck using the Advanced search to search on only posts made by him in this forum with some key words you think are pertinent and sort the output based on relevancy. Also remember that two or more words contained in quotes are treated differently than non-quoted words... the search thing here is nowhere near as good as Google.

 

In fact, I frequently use Google to find things in FTE.

 

Here are two pictures from the factory wiring diagrams shop manual, it differentiates only between heater-only and heater-with-AC. I hope you can read them, let me know if not....

BUT BE WARNED... 1980 is a one-year wonder concerning wiring, and these 1981 diagrams may not be totally accurate for a 1980... or, they may be 100% accurate, I really don't know for certain...

 

Those do help! now, tomorrow to dig in with the VM and testlight.

 

Ctubutis, those diagrams were a godsend. I now have all 3 speeds of outside fan, 3 speeds on inside fan and off.

Now, for something strange....With my Dealer Air, it seems the dealer converted it to a switched HOT. Maybe so the inside blower gets power without another 12V line.

The orange/blue 12V+ that usually goes to the blower first, now goes into what was the main ground of the HVAC unit switch, through the switch, out of the switch, to the relay pack, which splits to the remaining factory HVAC wiring, through the resistors, BACK into the orange/blue to the fan under the dash, and the fan is grounded through the frame. All of these connections are wrapped in factory looking tape, are using higher end crimped connections, that are all wrapped in self-vulcanising(*sp) electrical tape. It looks better than some factory looms I have seen.

If this was done by Ford, or a ford dealer, or some aftermarket company or some individual installing a JCwhitney kit is a mystery.

The only reason I can see to do this is to snag power for the inside blower from the existing fan 12V source under the dash and to keep the use of the blower resistors without another bank of resistors.

The microswitch that selects heat or AC uses the same 12V orange/blue Fan powersource as well.

The above diagrams match for color for the fan circuit as well.



My head hurts.......

 

Well, I'm glad you got it figured out.

In general, a dealer-installed accessory like this will be installed as per the instructions provided by the factory, this is for warranty purposes and is the only way a dealer would warranty the installation.

But it sounds like it was installed by the local Sears Automotive (or whatever) and there is therefore no telling what you've got. But I'm glad you seem to have the skills & abilities to diagnose it with the diagrams.

 

Thanks!

I probably should give what fixed here...
It was a bad connection in the resistor pack plug. crimped the sockets and cleaned the resistor pins and it worked great.
I found out it was switched hot when I was checking voltages under the hood on the 12V+ Fan Feed(orange/blue) and saw what should be battery voltage across to chassis ground drop when the switch was moved off of high. Knowing it was switched hot then figuring out the wiring was easy. Flip the diagram above from ground to hot.


Whomever installed it must have cut teeth on GM's

When my new fan comes in from Autozone, then the dash will not sound like a marital aid (fan is missing 5-6 blades in random spots).

Autozone is closing out the Metal non-AC underhood blower wheels for 13.00 by the way. Sell until depleted.

Thanks again for the diagrams!

 

Glad you got it fixed. Sometimes even simple circuits are hard to diagnose when you have a little something wrong - like ground. It can really make the symptoms seem bizarre when your frame of reference is off.