My a/c has always worked well since I've owned the car. Harrison compressor. Took a trip on Friday and in heavy stop and go traffic on a hot day (90F ambient) my temperature gauge was starting to rise. Got up to about 215F and traffic wasn't letting up. I was pulling off the highway to get out of the traffic for a bit and my a/c suddenly went warm and remains the same. The compressor clutch is no longer engaging. I have a limited tool kit with me and no service manual and was looking for any easy tests to conduct. I do have a multimeter in the kit. Nothing looks out of the ordinary as far as the wiring between compressor and wire harness.

Does the fact it went out while the engine temp was higher than normal provide any clues? The engine typically maintains temps fine except in that situation - hot day and not moving enough. Never a problem when moving. I had already been planning to pull the radiator and check it out. The PO installed twin electric fans in lieu of the stock mechanical fan, but they look like no-name parts and feel pretty weak.

Thanks for any input. Paul

 

Hi Paul!
Since you live in about the same climate like new mexico, I have some
pointers for you.

Since 1978 on my xj6 I always make it a point to flush the radiator
and engine block with the flush solution you buy, fill the system with
water and solution mix and drive a few miles to circulate it.

Drain everything out including heater water, so the water valve open.

Fill with new antifreeze. Try to flush every 3 years.

Your fans should come on when gauge reaches a little above L on the gauge.
That is normal when they shut off again after a few minutes.

Walter

 

First check is the 50 amp fuse in the rhs fuse panel.

 

Thanks, I did check the fuses at the rhs side panel and even swapped out new ones but compressor still doesn't engage. The blowers still operate at low, auto and high settings. I haven't checked the fuses behind the cheek panels yet. I can still hear the servo move when I change the temperature dial.

 

The fuse behind the LH cheek panel must be OK as you hear the servo whir.

Go ahead and check the last fuse, behind the RH cheek panel. It's clipped to the side of the HVAC case.

If the fuse is OK we can go deeper.

Do you have 12v test light or meter?

Does your car still have the 3-terminal thermal limiter fuse clipped to the a/c compressor bracket? It should, but some cars have been changed over to the later protection circuit.

But check the RH cheek panel fuse first. That's the easiest place to begin

Cheers
DD

 

Thanks for the responses. The fuse behind the passenger side cheek panel checked out ok.

I do have a 12v test lamp. I don't see a 3-terminal thermal limited fuse. Just the 2 spade connectors at the compressor. A green wire runs from one spade to a splicer. From there one wire runs to the Relay for the twin electric fans, presumably to turn the fans on anytime the climate control is turned on. The fans still do come on when the cc is turned on. The second wire from the splicer runs along in front of the water pump and eventually into a wire harness and disappears into the passenger/right side fender well.

The wire from the second spade seems to terminate at the compressor itself. I'll have to get a better look from underneath.

 

Second photo shows the wire from the second spade seeming to terminate at the compressor, behind the pulley. A quick spray of the spades and connectors with electrical cleaner didn't make a difference yet.

 

I saw this thread yesterday while multi "tasking". Watching the SF Giant baseball debacle and reading on my venerable lap top. Typing on it is a challenge.


Thoughts:


1. 90's in the semi arid New Mexico climate is far more tolerable than the same in humid Georgia. As to mammals, that is. Our metal critters do not discriminate.


2. No name E fans can move a lot of air. Controls and shrouding is very important.


3. Our front hinged Jaguar's have a way of dealing with climbing coolant temperatures in slow congested travel. Pop the bonnet to the safety catch. This allows far better air movement. Been there done that, albeit when it was still DOHC and engine driven fan.


4. Check the refrigerant level. Most AC's have devices to shut down the compressor if the level is low or gone...


5. Many such systems can be "jumped' to make the clutch engage, if is is still functional. A test only, and only for a brief interval. Far better to put a guage on it.


Carl

 

That green wire goes all the way from the servo, snakes around through the firewall to the compressor to the AC clutch. It's the clutch power wire.

With the key on (without starting engine) and temp control set to coldest, you can jump it to any + source to see if the clutch engages. You should at least hear the CLUNK of the clutch engaging.
(';')

 

Just a quick question on the side:

Is the drive belt for the compressor still in one piece?

 

Inspect all the associated wiring.....it have have become brittle and broken. The compressor feed wire goes in front of the engine then rearward towards the distributor, then jumps over to the body with some other wires (oil pressure sender, tachomoter, etc). Broken wires are common, especially where the wires are near the engine in front.

Also.....

Those Scotch-Lock splicers are destructive and might've damaged the already fragile, brittle wires


Cheers
DD

 

Thanks for the replies. The clutch was not engaging when I tried jumping it. I was also getting 12V at the green wire. The wiring was brittle and a bit sloppy so I've redone part of it, with a proper connector at those two prongs at the compressor.

It was very low on freon, low enough to not kick on the compressor. I had my local guy recharge it and I'll pick it up today. It's been 3+ years since the last recharge, so I think I can live with that. I'll give a final report once I pick it up. Thanks again.

 

Two faults resolved. Good work.


Carl

 

AC compressors need to cycle on a more or less regular basis to keep the compressor seals lubricated. When the seal gets dry, all your refrigerant escapes, and you not only have to recharge the system but rebuild the compressor too. Relatively simple, but inconvenient.

Our Jags are better off in that than other brands of that era because the AC comes on winter or summer whenever, whereas other brands, one must deliberately Choose to operate AC. Over a long idle winter, lubricant disappears from compressor seal and the 2 parts stick together, which bond is broken (and thus often the seal) the first time one starts the compressor. It seems to work for about 3 minutes, but then you can hear all the freon escaping out the seal. Guess how I learned this!

Nix was freshly recharged just before I took possession in 2013, and she's still cooling us Just Fine, thank you very much! I drive her on clear days no matter the season, and I think that has helped keep her AC working.
(';')

 

I've had the car back about a week and a/c is working great. Seems the only problem was just the system being low on freon. The shop didn't see any noticeable leaks using the dye test. So, I'm still not sure if it was a coincidence that it went out while the engine was getting a little hot in heavy traffic. It went from very cold to warm in the span of a minute. The car was converted to R134 by the PO several years ago.

 

Some Harrison's have a mechanical high pressure relief valve. It the high temps resulted in sufficiently high pressure, you might have lost enough refrigerant to result in zero cooling. Don't know if you have such a valve. Also, I wonder if these are changed out to accommodate the higher pressures of R134A compared to the original R12?