[njsteve]

I could use the correct decal as well. Along with another one of the "button looking thing" leads as you called it originally. Mine broke off years ago and I have the black wire taped off at the end and not connected to the superheat switch on the back of the compressor. Unfortunately no one reproduces that wire end so I'd have to cut one off a used harness. And the system works fine without it being hooked up. It is designed to function as a fail safe in case the Freon leaks out. If the pressure goes beyond the limits, the terminal grounds out internally and blows the thermal limiter fuse, shutting off power to the compressor clutch.

[Held for Ransom]

http://cgi.ebay.com/ws/eBayISAPI.dll...m=272631349583

It's too bad they don't make that harness.

I have 1131106 listed as the '75 decal, but I don't know if it's the right one or not as Firebird should have had their own decal.

Found the decal that should be for your '75, 1131086.

[Pepi]

Mike,
Thanks for that ebay link. I was asking about that harness in some other forums and couldn't find anything. I am going to order one. Luckily can depin it and use my original brown wire and eliminate one of the black wires so it looks correct without any splices.

Karl

[77 Canamman]

[OVERULD]

Great input and ideas from all - thanks much. Planning to tackle this pretty soon as it is getting HOT in Georgia!

BJ

[unruhjonny]

Originally Posted by OVERULD

You guys are an awesome resource ...

Yes they are.

Originally Posted by njsteve

Why would you want to update to something that doesn't look anything near stock?
...

/\ this.

All day.

Every day.

[OVERULD]

Thinking I'll go with a correct reman compressor, new hose and O-rings, and get the wiring harness and decal that HFR posted, and hope the VIR, condenser and evaporator cores are all good. Once I get it installed, I'll take it to Gainesville Radiator for a vacuum and charge with R12 if no leaks.


BJ

[Held for Ransom]

Just make sure you use the correct number, 1131058, decal.

[OVERULD]

I finally got around to having the AC system checked today. A friend who has a nice shop behind his home evacuated the system which still had freon, but was low. I replaced the thermal limiter fuse and we gave the system a full charge of R134. The new limiter fuse heated up and self-sacrificed within a matter of moments. We determined that the compressor is never kicking in because the circuit that would normally energize the coil in the compressor clutch, is only getting about 11.4 volts DC. However at the battery, it is showing an output of 12.3 VDC. We ran a wire directly from the battery to the hot lead on the compressor clutch and we were able to hear the compressor cycling and we were getting good cold air out of my freshly cleaned AC Ducts. Now to get an expert on working on old Pontiacs who knows the AC systems and can figure out what is going on with this on. In the meantime, it's windows down for me boys!

[77 Canamman]

A 1974 system was never designed to cycle the clutch. How long was a vacuum drawn on the system after removing the R12? Were the O-rings replaced? Was the system oil changed from the mineral oil to ester oil? Hopefully you only put 80% of the recommended R12 charge amount in the system. If you put a full charge of R134, the limiter will blow quickly due to excessive high side pressure.

[OVERULD]

I didn't say that my clutch was failing to cycle. I said it is not engaging at all because of the 11.4 VDC on the wire going to it from wherever it originates. We ran direct Battery voltage of 12.3 VDC straight from the battery to the terminal on the clutch connection and the compressor engaged and began functioning properly. We ran it that way for maybe 30 seconds and confirmed that we were getting cooling air, then removed the jumper wire and stopped the test.

As for the charge, we put in 90% of the amount shown on the placard on the compressor. The placard showed 3.75 Pounds so we put in 3.375 pounds, or 3 pounds 6 ounces, instead of 3 pounds 12 ounces. We pulled a vacuum for about 15 minutes after evacuating the R134. This system was converted to R134 by a previous owner. See earlier posts in this thread. My plan was to go back to R12, however, in order to try to get the AC working for the trip to the TA Nats, I wanted to try recharging the system with R134 and replacing the limiter fuse to see if the system might work. We hit a snag when the compressor failed to engage. I'll pick it back up and trace the wiring issues after I get back from Dayton. And no, we didn't replace any O-Rings or swap out the oil. I hope to get to all of that at some point, but that wasn't the goal or purpose of this project.

So, here's the GREAT news: Weather for Dayton-Fairborn this weekend is Sunny, with highs in the mid seventies, and lows in the low 50s! No AC required!

BJ

[OVERULD]

Bringing this one back up again. I bought an original copy of the 1974 Pontiac Service Manual at the TA Nats and I've been reading up on the AC system superheat shut-off circuit.

Here are a couple photos from the service manual that show the correct back head for the compressor. Does anyone have a compressor with this style back head that you would be willing to sell - even just the head alone?





And here are the photos I posted earlier if the back head of my current compressor which Mike (HFR) identified as a 1969 compressor. Will the style back head I need fit this compressor?







BJ


Sent from my iPhone using Tapatalk

[OVERULD]

More help needed on this AC issue.

Here is a little recap with some numbers.
On 8/22, we checked the system and found it had some Freon in it, but it appeared to be low, so we evacuated the system, pulled a vacuum for 15 minutes and recharged the system with 3.6 pounds of Freon with leak locating dye added. I installed a new thermal limiter to replace the one that came with the car which was blown. When we then attempted to run the system, it wasn't activating the compressor clutch and we blew the new thermal limiter. We ran a jumper wire from the battery to the compressor clutch and got it to engage, and had cool air, which verified that the compressor would run and the system seemed to be ready to work if we could solve the electrical issue.

I ordered some more thermal limiter fuses to use in troubleshooting and today, we checked voltage on the "B" terminal and had 11.6 volts. So, we installed a new thermal limiter and fired up the system and it ran just fine without blowing the thermal limiter. The system began cooling and the air temp got down to 60 degrees, but the lines began to frost over and it stopped cooling. Our pressures were: high side - 220, low side - 30. As the lines froze up, the high side pressure dropped to 200.

We added a half pound and repeated the test. Our high side pressure went up to 225 and low side was still at 30, with good cooling until the lines begin to frost over again, and the high side again dropped to 200.

We then evacuated the system again, pulled a vacuum for 15 minutes and recharged the system with 3.9 pounds (3.75 lbs. on placard times 90% = 3.375 lbs. plus the .5 lbs that the machine holds in the lines = 3.875 lbs. which we rounded up to 3.9 on the machine). We ran the system again and got the same results: high side 225, low side 30 until the lines froze up and then our high side dropped to 200.

We know we have a good tight system as we checked for dye leaks with the blue light/yellow glasses and found no leaks anywhere. We know we have a good compressor because we have good high side pressures. We know that we don't have any lines clogged so now we are suspecting the VIR valve may be defective. The color of the refrigerant in the sight glass is a little bit towards a brownish green tint, but no bubbles. We get good cooling at idle (60 degrees and we suspect it would get lower with the car going down the road) until the lines start to frost over and our high side starts dropping to 200 and the system blows warm air.

One other thing I'll mention is that the air temp selector lever on the dash will not go all the way over to the full cold (left) side. I get resistance but can force it all the way, but as soon as I lift my finger, it springs back about a half an inch towards the warm side. I think that may be keeping the system from getting as cool as it could because it is still allowing warm air from the heater core into the ducts if that door is not fully closed. How to I adjust that lever/door?

Thanks,
BJ

[Held for Ransom]

Found a document and thought I'd post it here...

[Held for Ransom]

And, the rest.

[OVERULD]

Very good info Mike, thanks!

BJ

[ladytata]

Sounds dumb but have you read the glove box manual on a a/c car in 74? Could not figure out why the clutch was running, until I looked in the book, there’s a climate moisture depending on which vent you have it on