Replacing a/c Compressor 75 Eldorado

[Tpicks55]

I am replacing the ac compressor with a reman.  It came with some oil in it already.  It had a sticker on it stating "some oil is added to compressor, refer to label under hood for specific oil"  Well that sticker is long gone.  What have you guys done on your compressor replacements.  2nd question.  The old compressor had a terminal sticking out of the back end which had a wire attached to it.  I'm assuming its a ground?  its missing on reman compressor.  Thanks in advance for your input. Tony

[chrisntam]

Is your system R12 or R134?

Do you have a shop manual?  It explains compressor replacement, I highly recommend you get one if you don't have one.  It talks about draining the oil from the old compressor, measuring it, then depending on how much is drained, that will tell you how much to add back.  And drain the oil from the new compressor, add new oil according to the shop manual directions.  Make very sure what type of oil you need, it's dependent on the type of refrigerant you're using.

Be sure to change the desiccant bag in the VIR.

The wire in the back of the compressor is a switch.  Take out the plug in the reman compressor, remove the switch from the old compressor and put it in the reman compressor.  Be sure to relieve the pressure in both compressors prior to taking the switches out.  It's either a super heat switch or a pressure switch, not sure.

Why are you changing the compressor?  If there is metal in the system, you should flush they system before the new compressor is installed.

Get you a shop manual.

[The Tassie Devil(le)]

The wire in the back of the compressor is a switch.  Take out the plug in the reman compressor, remove the switch from the old compressor and put it in the reman compressor.  Be sure to relieve the pressure in both compressors prior to taking the switches out.  It's either a super heat switch or a pressure switch, not sure.

The switch operates when the pressure inside the compressor drops, indicating a loss of gas, and this blows the Fuse that is on the AC box on the left side of the firewall, near the hood hinge, and saves your compressor from being destroyed.

Came into being in the 1972 model year.

Bruce.

[Tpicks55]

Thanks for the replies it helps.  I'm converting the system to 134.  The system takes 525 oil in the manual but converting to 134 so what oil do I switch to??

["Cadillac Kid" Greg Surfas 15364]

Compressor rebuilder will designate oil 5to be used with R-134a.
Greg Surfas

[TJ Hopland]

I agree with Greg,  Ideally the compressor manufacturer should specify what they used for assembly and what and how much it shipped with.   I have played that game and many times there often isn't an answer.  It seems like a simple question and something that would be easy to answer or document.   Its not like the old days where you could have someone walk in the back and read the label on the jug they got the oil from. 

A few years ago I got my local Napa store manager interested in the subject.   I think he was actually a district manager for several stores so he likely had a little more access than your average bear.   After a week of research he came to the same conclusion as me, many times its apparently a secret.   Instructions say refer to OE manufacturers instructions which makes no sense since they were not the ones that made or remade the current compressor in question.  It may not even be the OE design, it may be a different model made to bolt in place of the original.    Its like saying you should put 40 weight air cooled oil in the LS6 you swapped into your Beetle.  I think the project that started this research was a 97 Chev truck (pretty rare right?).   He found places where it said that PAG 46 was the oil and other places where it was listed as PAG150.   The manager basically said if I tore up a compressor he would take it back and I would get credit even if the store didn't.

After asking around what I found is Ester 100 is very popular among non dealer type shops.   Its about as close to a universal oil as you can get.   Its in the middle of the weight range and doesn't tend to react with other types of oils.    That is what I have used on my last half dozen projects and some are going on 5 years now with no issues.   I will note that I have not personally use it with an A6 (60's-70's) compressor yet.   I have used it on R4's (80's-95), H6's(96-?), and Sandens.

Basically if you are lucky enough to know whats in the compressor and whats currently in the car or you are confident that its 100% flushed I would consider going with whats in the compressor.    If I don't know all those things for sure its Ester100.    I have had no formal training in this subject just telling you my experience.

[Tpicks55]

thanks TJ for the information.