1989 XJS,

I am trying to troubleshoot A/C.

1. I've got a constant 12v to the compressor wire with the ignition on. That doesn't seem right-any insight?

2. Where is the pressure switch?

3 where is A/C relay? Can't find either and am wondering if an idiot owner (either previous one or me) moved something and forgot about it.

 

re: pressure switch, I think I found it on the back of the old compressor. But my new A6 compressor from Amazon didn't have one installed.

Should I install a new switch or reuse old one?

Also, new question, are there two switches? high pressure and low pressure?

 

The pressure switch is a "High Side Low Pressure" type, meaning that it shuts off the compressor if there is low or no pressure on the high side to prevent the compressor from running empty. On the schematic, it sits between ground/earth and the compressor clutch. So it supplies the ground for the clutch to operate.

Looking at various peoples' Sanden conversions (on Jags and other makes), some have a switch installed somewhere on the high side of the system and wired to the clutch, and others just wired the clutch to ground. The switch seems like a good idea unless you want to replace the compressor the next time the system develops a leak.

 

So I don't NEED it unless there is a leak in system?

Then I'd just be out of a compressor? I could live with that for now, maybe I'll fix later.

Now, anybody have any insights as to why there would be a constant 12v to the compressor supply wire?

 

The voltage is supplied from the compressor relay. So I'd start there.

 

Where is the compressor relay located?

 

If you haven't done so, try turning the climate control mode switch to 'off'.

The climate control system is designed so that the compressor operates in all modes, even when heating is called for. The idea is to refrigerate and dehumidify all incoming air...and then heat it when heating is called for.

Also, if you have a convertible the compressor will be powered-up even if the mode switch is 'off'. This is to ensure that the fuel cooler ...which works off the refrigeration system....is always functional. The rationale is that an owner might well switch the system 'off' when cruising about with the op down....thus losing the benefit of the fuel cooler. Jaguar made this change sometime during 1989 calendar year as I recall.

Cheers
DD

 

IIRC, it's back near the ABS pump under a black plastic cover next to the starter relay.

 

Just reuse the old one. A snap ring holds it in place. Remove the ring and wiggle the switch out. A new o-ring would be nice.

The new compressor should have a blanking plug...also held in with a snap ring.... where the switch goes.

One caution: make sure the physical location of the switch hole is exactly the same on both compressors. Some A6 compressors used a superheat switch; others used the HSLP (High Side, Low Pressure) switch. The rear plate is different---there's a sight variation in the position of the hole. You have to match the switch to the compressor. If the hole isn't in exactly the same place then neither switch will work correctly if installed.

Your '89 should definitely have the HSLP type switch.

Cheers
DD

 

Thanks for tips on pressure switch.

I avoided problem with compressor clutch wiring by going back to the AC relay and running a new wire for compressor clutch. (I think I must have mucked up the original wiring when I replaced engine bay wires a year ago.)

So, got the wiring solved and clutch was engaging and then stopped again. No power out of AC relay. (relay has power coming in)

#11 fuse good, inline fuse behind kick panel good, swapped the AC relay. no change.

Am I missing a fuse or connector somewhere?

 

Is the system charged?

If it isn't, then perhaps the switch is performing it's intended purpose and shutting off the clutch because there isn't any pressure in the system.

If there is refrigerant in the system, then check that the wiring from the pressure switch is going to both the clutch in one direction, and a proper ground/earth in the other. The switch shuts off ground to the clutch.

 

I actually don't have a pressure switch at all, didn't/forgot to install when I replaced the compressor.

I WAS getting a 12v signal out of the A/C relay (brown/green wire) when turning on the fan switch and in the midst of working on the wiring I think I messed something up.

Now, no voltage from the A/C relay where fan switched on.

This car is testing my patience presently....

 

Check if you have 12v at the socket for pin 87 of the relay.

 

No, do not have 12v at 87 socket.

I don't want to confuse things but on my diagram the 87 socket should be a brown/slate wire from the start relay. On my car its a green white wire.

The brown/slate wire runs into the 30 socket ands I do have 12v there (as the manual suggests).

 

Here is a picture of relay:

 

Check if you have 12v at the inline fuse

 

Yes, 12 v from inline fuse.

 

That must be your problem. According to the schematic, you should be getting 12v to pin 87 and then when the relay triggers it delivers 12v to pin 30

 

Is the wire from the fuse going to socket 87?

 

Wire from fuse is going to socket #30,

socket #87 is a green/white wire.

Is schematic wrong?

Also, does it matter?

I tested the really earlier when working on wiring. When A/C was switched on I was getting 12v from the 85 and 87 socket, with AC switch off I only got 12v to the brown/slate wire which is #30.

It seemed to work earlier but after I ran a new wire from the brown/green wire leaving the relay it stopped working.

i must be doing something stupid and/or wrong.