Know of any instructions or videos explaining the procedure? There's not a lot of room to work.

The PO bypassed the heater switch by running a wire from the battery to under the dash, and another wire from under the dash to the blower motor. To make the fan work, just touch the two wires together.

I'm trying to figure out why he bypassed it in the first place. It seems like the control unit is not sending power to the fan switch, so I'd like to remove it, and test it.

This is for an 84 T/A

 

Most likely, it's the wire that feeds power to the control head, not the control head itself.

That said, the eeeeeziest way to get in there and trace it, is in fact, by removing the CH.

I'm not sure how it mounts in the Firebirds; in the Camaro, it's just held in with 4 screws, just like the radio faceplate; and just pulls out, far enough at least to reach up in there and do what you gotta do.

Which is: on the "mode" switch, there's a harness with a green wire that goes to the compressor, a wire that goes to the fan switch (since the fan is turned off if the "mode" is "off"), and a brown wire. That last is the power supply. Follow it up into the dash. About a foot or so up in there, it plugs into the main dash harness. (remember, the AC harness is separate, since it's installed all on its own as part of the AC system, which is an option and therefore is a stand-alone assy) Observe this plug carefully. It is the most stupendous example of flawed electrical engineering I have ever seen in cars other than old Frods. it is so incredibly stoooopid. For starters it's altogether too small and inadequate to begin with, which is bad enough all on its own. But the crappiness doesn't end there. In violation of all common sense and principles of reliability, instead of the metal parts of the it providing the tension holding them in contact, the plastic does!!! (which is to say, doesn't) the plastic of course cold-flows, which relieves the tension, which reduces the connection effectiveness, which allows its resistance to increase, which makes it get hot in operation, which aggravates the cold-flow process by turning it into hot-flow, which further reduces the tension, which makes it get even hotter, which melts the plastic, which reduces the tension even more, which makes the connection even worse, which makes it get REALLY hot, which eventually burns the connector body to ash, which makes the tension disappear completely, which eventually allows the metal parts to not even TOUCH any more.

The cure of course is to COMPLETELY GET RID OF the stupidity. Get a pair of the BIG FAT WIDE THICK HEAVY-DUTY yellow slide connectors - not the little narrow thin weenie ones that are exactly like the red and blue ones except yellow, it needs to be the BIG FAT WIDE THICK HEAVY-DUTY ones - and cut off the stoooopid ones, and replace them completely. Make sure to use insulated ones, or if not, wrap them REAL GOOD in electrical tape.

Then once you have amazed yourself by getting the whole system to work except for the fan high-speed setting, go out under the hood, and find the blower motor. It has a purple wire. Follow that wire to a plug that plugs into a little box. That's the high-speed relay. In the same plug with the purple wire, find the big fat red wire. That's the battery feed for high speed. Follow that wire toward the driver's side, along the bottom of the windshield cowl. About right above the pass side valve cover, you'll find another of the same design connectors, which will probably be even worse burnt up than the one under the dash. Replace that one the same way.

At one time there were 7 80s GM cars in my immediate family. Out of the 7, 4 of them had already failed this way, and had no AC at all. I spent a couple of hours one afternoon repairing all 4 (both connectors), all of which then worked like brand-new. I then looked at the other 3: one was within a few hours of failing altogether itself (the connector visibly smoked if the fan was on the 3rd speed, which is the one that draws the most current); one already had no high-speed, although the other speeds still worked; and I just went ahead and did the same thing to the 3rd, whose connectors were only moderately melted. In ONE DRIVEWAY, 7 out of 7...

I hope the idiot that designed those connectors spends his eternity in Hell with a nice car air conditioner in his cell that doesn't work because those connectors are burned up, and they're out in the open where he can see them, but he just barely can't quite reach them to replace them with something that actually works.

 

Yeah, the connectors need replaced, but I'm not convinced it will solve the problem.

I have power at the fuze but no power on the hot side of the connector. I think I will cut-off the connector anyways, and test it again.

But there also seems to be no continuity through the control head. I tested using the brown wire going in, and the brown and white wire going out.

Before I do anything rash, I think I will replace those connectors and hopefully, I'll get better readings.

 

So I replaced the connectors, which are located in the same space as the stereo. I now have power to the connector.

On the other hand, I'm pretty sure I'll have to replace the control head. After replacing the connector, I still get quite a bit of resistance and it changes as I move the selector lever back and forth.

Not looking forward to replacing this, because it is held in with various clips that are hard to get at. Also, I don't think I can get a new or rebuilt unit.

I think I'm going to clean-up the rest of the heater wiring and see if it magically works.

 

Post a pic of the connectors you cut out... it'd be interesting to see how destroyed your particular ones were.

 

 

So I put everything back together and IT WORKS!

Except for High, that is. The relay works but no power from the fusible link red wire. I will save that one for another day... My goal for today is to get rid of as much questionable wiring as possible.

In tracing the wires, I noticed that he had hard wired the cooling fan directly into a wire under the dash.... no thermostat. The cooling fan has never worked. As I unraveled some electrical tape, I discovered he had spliced the wire using too small of a connector, and the wire was loose.

So I guess the cooling circuit is next on my list.