My compressor is not turning on. After a late night searching archives Im still not clear on how to jump the compressor. My retired H+A friend stopped by yesterday and took a very quick peek said that I should jump the positive wire coming off the compressor to the battery. It looks like someone had done this in the past cuz the wires were stripped back. When I do this nothing happens. The wire actually has +12v going through it already. Am I supposed to arc across the pos. and neg. leads somewhere?
I do know that I have a really slow leak and want to try jumping the compressor to see if it will pull more coolant in. I am aware the hazards of jumping it for too long.
The low port reads like 60psi but I understand that that reading does not mean anything until the compressor kicks on.
Also FYI its on 134a and the only fuse I found blown was the aux fan fuse.

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

Yes, that 60 reading if it has been sitting a long time without compressing is what the two ( high and low ) have averaged out at.... and I don't know of any references as to what that usually is... all the important measurements happen after your compressor is working.

You should be able to run a wire from the positive post on the battery to that compressor wire...and hear a click meaning that your magnetic clutch is engaging...

However, I would check to see if the compressor will turn a little by hand first..look at the inside part of the clutch area near the shaft...

Since it looks like someone else has tried addressing something wrong I would go slowly and carefully to keep from possibly causing more damage.

How long has it been since you had cold air ?

at 60psi you should have continuity across your pressure switch, easy to check with a meter. You can load check your line with an old headlight, it draws about what the clutch does.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

So, switch is "A" in the attached picture, is that correct?

Front of compressor can be turned by hand.

AC was working as of 1 month ago. I just got back from 2 weeks out of town. Was charged in May last year by a retired H+A guy who changed the oil to a compatable oil for 134. and charged with what he described as a coolant that was a sort of hybrid that is compatable with 12 and 134. He said I had a real slow leak and I could probably limp along with 134 charge ups when needed. I don't think I have added any since last summer.

Engine running AC on. 12v+ on both posts of "A"
Engine running AC on. 12v+ at wire "B" to compressor.
Engine running AC on. Continuity between posts of "A"

Engine running AC off. No voltage at posts of "A"
Engine running AC off. No voltage at wire "B"

Engine running AC on. Wire from positive batt. post to wire "B", no click.
Engine running AC off. Wire from positive batt. post to wire "B", no click.
Engine off. Wire from positive batt. post to wire "B", no click.

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

"described as a coolant that was a sort of hybrid that is compatable with 12 and 134."

I do a lot of reading about automotive AC... I do not think a critter like that exists... one that will satisfy all the harsh requirements of an automobile AC.. mix and carry the oil around correctly, condense and evaporate at the right temperatures, have working pressures which will allow long compressor life.. etc... the requirements are pretty stringent ... thus all the AC threads....

So first I would find out from him what he used... this is also important if you take it to an AC shop... you do not want to contaminate their equipment.. be sure to warn them if you do...

The other items like engine running, etc.. should have no effect on the basic first test.. running the positive wire to the compressor wire... if you don't get a click then something is wrong with the compressor clutch activation and needs to be addressed first... because unless it is working you can't do much with the rest of the system diagnosing...

Agreed. In not sure where that leaves me though. Im not sure if my original question was directly answered. Is the procedure for jumping the compressor the connecting of the positive wire to the compressor to the positive battery post?
If it doesn't seem "locked up" but sending power to it doesnt do anything Im not sure where to go next.

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

From post number 2 :

"You should be able to run a wire from the positive post on the battery to that compressor wire...and hear a click meaning that your magnetic clutch is engaging..."--ME

If your compressor clutch is not able to engage by the application of 12 volts to that wire then you may need to take the compressor off and take it to someone to check it further...
If you have the proper tools the CLUTCH ALONE can be taken off the compressor... assuming you think the compressor is ok and you want to save a lot of work.