Advice on air conditioner compressor for 1987 series 3 XJ6

The a/c ceased to blow hot air yesterday, took it to an a/c shop I’ve been using for many years. Shop owner said the compressor clutch has gone bad, the ‘good’ news is the compressor itself appears to still have plenty of refrigerant in it, which he says he can vacuum and reuse, saving me a few $$$. He said his supplier wants $800 for a compressor (wouldn’t tell me the brand) but readily admitted I could find one on line for substantially less and if I wanted to take that route he’d be ok with it, but, of course, he would not offer me any warranty. I called one of the ‘usual’ suppliers, he told me there are aluminum ones for $200.00 to $250.00, but they don’t carry them any more due to too many failed units within periods of less than a year. He said now they only sell GM Harrison units, at $450.00 each, but they are better units & last a long time. Any constructive ad vice on what I should do would be welcome. Thanks…

Did you consider replacing just the clutch? Sometimes it can be done while the compressor is still on the car, in which case you needn’t remove the coolant. Might try to find out why the clutch is bad–slipping, burned out coil etc.

BTW, I hadn’t heard much bad about the aluminum replacements for the Harrison A6 in terms of reliability. They are new; I don’t think you can buy new A6 compressors from the original manufacturer.

The aluminum ones have less output at idle speed, though–the original A6 was the equivalent of 5 tons–a large home unit. IMHO.

Thank you for your reply, Robert. I’d be thrilled to just have to replace the clutch, but this a/c technician keeps claiming even to do that the compressor would have to be removed from the car. The pulley on my current compressor appears to have a gap between it and the compressor .The a/c technician said nothing about the burned out coil, though I’d suspect that could be an issue as well. If so, would the compressor have to be removed from the car? BTW SNG Barratt sells the Harrison A6 manufactured by GM, I think, and they told me they would no longer sell the cheaper aluminum replacements due to numerous failures and returns on the aluminum units. Any further thoughts on this situation? I’m still in a quandary what to do.

The compressor clutch is electromagnetically operated, incorporating the coil…

‘The AC ceased to blow hot air…’ is a misprint - it’s not a sign of a failed compressor clutch…

Testing the clutch is a matter of turning AC ‘on’ - the idle rpms should drop, indicating clutch engaging. And disengaging, raising idle, when turned off…

The a/c technician may prefer to take the compressor out for whatever work is to be done, which is fair - it is pretty cramped in there. It may still be possible to do the work without emptying the system - which is of course necessary if the compressor must be changed.

The GM Harrison compressor, as offered from Barratt, is in my opinion about as good as it gets - though in principle; the technician may consider a rebuild of the one you have may be worth while…?

xj6 85 Sov Europe (UK/NZ)


My Jeep has the AC compressor high and visible. Not a GM unit, though. I can see the clutch engage and disengage. In response to the internal command. It also has an on/off option by a button.

Point. I realize the unit in your car is not easily seen. But a mirror or borescope to look???


Yes, I know the RPM’s should drop when a/c is turned on. On the day the a/c suddenly failed that was the 1st thing I looked for, and when the RPM’s did not drop, I was concerned perhaps the compressor failed, sprung a leak, and with no RPM drop when turning on the a/c, I was concerned perhaps al the R12 was now lost as well. When the technician had me turn on the a/c (even though it was not working) he had his pressure gauges hooked up to the system, and postulated there is a good chance most of the R12 is still in there. He hooked up a pair of wires to the battery and somewhere else ( I could not see from where I was sitting in the driver seat), then told me to shut the engine off & come out & have a look under the hood with him. With a flash light he pointed to the front of the compressor and showed me a gap which should not exist between the pulley and the body of the compressor. He then said the compressor clutch had failed . Despite the ridiculous quote he gave me of $800.00 for a new compressor (that’s just the part not the labor) he said he’d have no problem if I chose to bring my own compressor from elsewhere in which case he’d be willing to install it & just charge me labor. He admitted many of his customers have gone the same route, with such a price quote it isn’t difficult to understand why. To justify the $800.00 quote he said if he supplied the compressor he’d include a one year warranty for replacement and installation if anything went wrong, but if he used my supplied compressor he would not offer a warranty. When I asked him what brand compressor he would use, he wouldn’t tell me, just saying, “I’d have to shop for one.” What??? If the GM Harrison is the gold standard , I think I’ll take my chances and buy one from SNG & have this technician install it. While I’m at it, would you recommend replacing the receiver dryer at the same time? Both the current failed compressor and receiver dryer and expansion valve were all replaced 12 years ago. During that time I never had to add R12 to the perfectly functioning system. This may also be due to running the a/c once a week (at least) during that time period. What do you think?

There is supposed to be a gap when the clutch is not engaged. The coil (electromagnet), when activated by applying 12V to a pair of male 1/4 inch spade terminals, pulls a plate attached to the pulley into contact with a matching plate on the compressor shaft. The gap then disappears.

Your tech was presumably applying 12V to the coil, and confirming that it didn’t “pull in.” That means the coil is open circuit. But that assumes he did it right. For example, he might have assumed that the existing ground connection was intact when it wasn’t. If you have an ohmmeter, put its leads on the two spade terminals (the connector pulls straight off to expose them) and see if it reads (should be a few ohms). Or connect 12V to one terminal and ground to the other (doesn’t matter which)–the clutch should move and click loudly). There are, depending on the year, various safety switches that deliberately interrupt the 12V or ground to the clutch coil to protect the compressor from too high temperature, and or too little refrigerant charge. These could cause your problem, but applying ohmmeter or voltage directly to the coil should bypass them.

If your tech did it right, he showed you that the coil needs replacement. No reason IMO to replace the compressor itself. But I’d confirm that he did it right as described above.

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Bob’s explanation is similar to mine, but in far better detail.

And, if it is a compressor failure, junk is floating about. Fush some replace others… ,

R134 conversion time? Or another? r12 is a lot of$'s nowadays…


If the coil needs replacement, could it be done without having to remove the compressor from the car?

Did you check if the compressor thermal fuse is not blown ? It’s mounted right beside the compressor.
Also did you check the car’s fuses?

Did your techman apply 12V directly to the coil?
When he said the clutch is kaput did he said witch part ? i.e. electric or mechanical part?
It’s very easy to check yourself, apply 12V to the two cables that go to the clutch and you should hear it engage and the gap disappear.

There should be a gap there, albeit not big, and it’s adjustable from the front of the compressor.
If I was you, and if indeed the clutch is bad and beyond repair, I would go to a A/C shop to empty the R12, get the A6 compressor from SNG Barrat, a receiver dryer, new O-rings for the hose fittings, two R14 ports and do it my self, then go back to the shop to re-charge your system with oil and R14.
It’s a very straight forward job, and that’s what I actually did when my compressor started sounding like a drum machine.


Simple test; with ign ‘on’ but engine not running turn AC ‘on’. There should be a distinct ‘clunk’ as the clutch engages…

If there is no response; check the electrics, as Aristides suggests! There are two main reasons for no idle drop; compressor fails to engage and no refrigerant resisting compressor turning.

The receiver/drier must(!) be changed whenever the system has been opened. And the system leak tested before refill - R12 may not be available; the technician may have to convert it.

And running the AC weekly is an insurance against seal deterioration…

xj6 85 Sov Europe (UK/NZ)

Thank you for your reply. He did apply 12V to the coil. Yesterday I opened the hood of this '87 car parked next to my 1986 XJ6 to compare the looks of the compressors on both cars. The gap on the 1987 car is quite large compared to the one on the functioning '86 car. I’m ready to accept the compressor is not as It should be, and I have no interest in paying $$$ in labor charges to have the old one pulled out and repaired. It would seem to make sense to purchase a new Harrison GM A6 unit and have him install it with the R12 he’s willing to evacuate and save from the system . will keep you updated. Thanks again

The technician did test the electrics, and he also hooked up pressure gauges to the system which indicated there is plenty of R12 in the system. As I indicated in my reply to Aristedes, I compared the look of the compressor on this car to the one on my functioning '86 car. The difference was quite noticeable. It would seem the GM Harrison A6 unit would be the proper course of action to pursue now. Of course the receiver/drier would be changed at the same time. Would it be necessary to change the expansion valve as well? It was changed when the current compressor was installed on the car.

Looks like the decision is made but this is interesting none the less. It looks like the clutch is mechanically damaged or in need of adjustment, AND the coil is burnt out. Odd that both would happen at the same time. The gap should be about the same as a sparking plug–0.025-0.030 inches. Too wide and it won’t pull in. It can be easily adjusted with the proper tool. Of course since coil has also failed, adjustment won’t help.

Yes, but was the coil good or not?
Because if the gap is too big, as Robert suggests, the coil can’t pull the plate, it’s just a matter of adjustment and easily fixable.

If the expansion valve is new you don’t need to change it.

I suggest again to get the adapters and re-fill the system with R134a.
It’s more environment friendly, less expensive and much easier to maintain, as it’s he norm today.
You can leave the original expansion valve, the system will work OK (that’s what I did), but it will work better if you change it with one specific for R134a.

The electrics just engages the clutch - if it does not do anything else. The presence of refrigerant indicates ‘[no leaks’. However, replacing the compressor empties the system, and the receiver/drier must be changed…

Actually; two types of compressor safety devises were used - working ‘opposite’. The thermal fuse, mounted at the compressor, cuts power to the compressor clutch.

The pressure switch, in the rear inside the compressor, cuts clutch ground. If this fails, or is disconnected; applying power to the clutch will not engage it…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

So here’s what to do first:
-measure the gap and report back.
-find out how to measure the resistance of the clutch. Bypassing the fuse.
-if resistance is neither very close to zero nor infinite (how much does the clutch need-10A@12V?), the coil is good.
-check the compressor fuse.
-realign the clutch.
-if the multimeter says the clutch is shot, try to install a new one.
If a new compressor is needed, get a dryer too - always. R12 is better because you don’t have to change anything; seals, the expansion valve and the same system really is designed for R12. With an oil change, new seals and maybe hoses there’s no reason for R134a. Cheaper to refill, too. As per Aristides.
And I’d take the A6 unless you had something else from new.


So, please clarify: even if the clutch can be tightened, if the pressure switch in the rear inside the compressor has failed, then compressor would still have to be removed to repair/replace it. If that’s the case (please confirm), and there is no way to remedy the situation without removing the compressor from the car, then I’d just as soon have him put a new GM Harrison compressor in. He has the items required to remove and save the R12 from the old compressor, and I don’t see the sense of paying a sum of $$$ for labor to remove, repair, and replace the old clutch living with the possibility of another item in the old compressor having a strong possibility of failing at some point as well. Does this outlook make sense?

There are two wires connected to the clutch. Apply +12 to one (green?), and ground to the other. If there is no response; the clutch itself has failed - it’s immaterial which protection device is fitted…

The clutch simply clamps the freewheeling pulley to the compressor proper - it is not adjustable. Whether replacing a defective clutch is worth while is arguable - but a technician may insist on removing the compressor to repair. Which likely means emptying the system - as I suspect is the case with replacement of either safety sensors…

As an aside; if the technician has a supply of R12 - fair enough. But is improbable that the remaining R12 is adequate for a proper fill…however…

xj6 85 Sov Europe (UK/NZ)

xj6 85 Sov Europe (UK/NZ)

Just to clear up a couple of things it is important that you get a professional to change the compressor. He will take out the refrigerant and put it back in saving you some dollars. Ask him if he uses a dedicated clean recovery bottle dedicated to R12 so as to not contaminate your refrigerant. As the system is still charged you do not need to change the expansion valve or the filter drier. The system must be evacuated to 500 microns with a vac pump and hold for at least an hour. Then the original charge can be put back in.
Filter driers only need to be changed if they have had to absorb a fair bit of moisture or acids, etc. Evacuating the system properly is paramount.
Expansion or TX valves only need to be changed if they fail. I haven’t had to change one in any of my cars in the past 38 years. It is the whipping boy of all faults and the cause of few.
If you go to R134a then change the TX valve and drier and flush the lines. It uses a different type of oil and the old mineral oil does not mix with it.
If you get a new compressor yourself make sure the oil is good for R12 if that is the way you are going to stay.