First off I'm new to this site so bare with me. The car in question a 71 supreme when I bought it the a/c is disconnected the lazy way... They just cut all the wires for some odd reason. What my question is does anyone have pictures of where said wires go or a diagram? I've used the search but a lot of it comes up headlight wiring and all that, that I can't descipher any help would be appreciated this FL heats a killer lol

 

I don't have a wire diagram but I can take pictures of any are you want if your a/c system is like mine, mine is a 1972 cutlass supreme with a 350

 

That's exactly what I was looking for but now that I see it it didn't help like a thought it would lol clean motor none the less

 

These pictures are just to see if your is like mine.. The wiring should be simple I only see one wire coming from the firewall to the a/c unit where it goes into a two prong plug them then the other wire from that prong goes to the thermo limiter fuse where now you will have three wire, the one to the thermo limiter fuse,one to the a/c compressor in the front and the other to the back of the compressor. I think it's called the Heatsink

 

If you could get me pictures of where a wire starts then ends would be great. I'd love to give you more detail of what I'm looking for but I really don't have a place to start since there all over the place, trying to get pictures to explain a little better

 

I'll try to post some more detail pictures.. There is a website called, wildaboutcars.com its free to join and you can download the wire diagram from the chassis manual for free.. It might be easier for you to try to locate a wire harness for the A/C and that should have all the correct plugs you need and make for a simple installation

 

Okay I so there is more wires to this than I thought, I followed the wire harness and found another plug that I thought went somewhere else.. I hope these pictures help... The new plug I found has a green,blue,black with a blue stripe and a black with a green stripe. The other two prong one has a green and a brown wire if I'm correct the green comes from the wire harness and the brown goes to the thermo limiter switch

 

The black round plug goes behind the compressor I believe it's called the heat switch

 

As ridiculous as it sounds were on to something. Where does image 472 plug into?

 

I breezed through wildaboutcars, good info but not as detailed as I need. As far as wiring harness that's the route I'd like to go but so far I haven't had luck finding just ac.

 

On the back of the a/c compressor.. There is a small pin that fits in that fitting

 

As Al says, on the '71 or '72 and later models there is a pressure switch on the back of the compressor, and that plug connects to it.

The low-pressure-safety system introduced on these models is exceptionally lame, causing a fuse (in that little black plastic box) to blow if your pressure drops too low, and it is entirely reasonable to run without it, or to rewire it to work in a more straightforward manner.

- Eric

 

hmmm I do not have that connector or plug-in..

 

that's what im working with so if im not sounding like I know whats what its because I get the joy to play with all that spaghetti of wires

 

Find each wire, give it a good wipe with lacquer thinner, so you can see what color it really it, clean up whatever plug is on the end, and photograph each one, then post them up here, and we'll tell you where they all go.

- Eric

 

Eric, do you any suggestions on how to eliminate,bypass or re-wire it.. Mine keeps blowing the thermo limiter fuse and I know it's got plenty of charge because my friend just did it.. Or should I try re placing the heat switch on the compressor

 

that's what I have in questions

 

On image 636 what does the inside of that plug look like and how long is that wire, does one end come from the firewall ? And on image 637 that wire looks cut and it looks like it's coming from behind the compressor exactly where the heat pressure switch should be, try reaching in there and pull it out

 

637 is 1 black wiring coming from the compressor 636 looks like |-- almost like a T

 

Hi Al.

The superheat switch is designed to sense the low-side pressure and to close (connect to ground) when the low-side pressure drops to -1psi to -5psi, which equates to a vacuum of 2" to 10" of mercury.

When the switch closes (grounds out), it shorts the power to the clutch coil to ground, through a fuse and a resistor, which are connected in parallel. This fuse / resistor combination creates a very-slow-blow fuse which should take about 2 minutes to blow, so that momentary drops in pressure won't blow the fuse.

The idea is to protect the compressor from two potentially fatal conditions:
1. low refrigerant, and
2. a blocked POA valve,
and thus save GM significant money on warranty repairs for these problems.
If the low-side pressure goes to vacuum for too long, the fuse will blow, disabling the compressor, and mandating that the customer bring the car in to the dealer to have it checked.

If your fuse keeps blowing, it could be for a number of reasons:

• The parallel resistor has burned out, is no longer connected, or is missing
• Your POA valve is misbehaving, and sticking closed for too long
• Your refrigerant is low
• Your superheat switch (SunAir part #MC-1316) is not working right.

You can test your switch with a gauge set, which will also let you see whether your low-side pressures are staying too low, and whether your refrigerant is charged.

I have no idea how an R-134 swap would affect low-side pressures, but if it makes them low, and you've switched to R-134, that may be your problem, too.

Bottom line: If you unplug the superheat switch, it will no longer trouble you, BUT if there is something wrong with the system, your sheep will be eaten after you have killed the little boy who cried "Wolf!"

- Eric

 

Look at the passenger side of the ac unit on the firewall and see if you see any plug connections or somewhere where you can connect a plug, your is a little different than mine but I think it's the same idea, the big plug on mine comes from the firewall and connects the the ac unit and right above that connection is the small one that sends power to the compressor. Try removing the plug on image 637 answer see what that looks like,it should twist right off

 

Here is the diag for 72 - should be very similar.
https://classicoldsmobile.com/forums...tml#post308282
The superheat switch connector is at the rear of the compressor, under the pipe fittings. It is a single terminal, unless the compressor was replaced with a different one.

 

Eric, where would the parallel resistor be located? Never checked that

 

With the red cap unscrewed , it's threaded on the inside until a valve like on a tire valve stem there are no connectors in that area on the firewall other than the black wire which looks like a ground.

Rob we're already in too deep for fancy diagrams

 

Rob, is that on the 1972 chassis manual, if it is I got to get me one, good info..

 

It's in the little black plastic box, right next to the fuse.

- Eric

 

I'm confused, don't know what black plastic box or fuse

 

But, just above, you said:
If it keeps blowing the fuse, one would expect that you know where the fuse is.

In that little 1½"x2" black plastic box with the fuse, there is also a resistor.

- Eric

 

This is the fuse that keeps blowing every time I don't see a black box

 

Oh. It's a single unit.

I've never seen that - either it's a later change, or it's completely normal, and I've only seen a few oddballs.

That is the same part, but the ones I've seen have been in a little plastic box that snaps open, and has inside of it a cartridge fuse and a resistor.
In your case, both are contained in a single disposable package (which I think goes for about four bucks).

I tried to find some pictures of the one I'm thinking of on line, but I found nothing - maybe I'm nuts.

Sorry for the confusion.

- Eric

 

Yes. THE Bible for your car!

 

Does any of these look familiar on your car?

 

If your asking me no

 

The last picture (of the compressor rear) shows the superheat switch pin under the top two holes to the right. If yours does not have that pin, a different type of compressor was added on.