Hi All,

I recently upgraded the AC system on my 92 V12 to a Sanden compressor with new hoses and drier and I cleaned out the expansion valve which had a small amount of particles.

It was re-gassed with R134a and worked well initially, super cold.

But after about 20 minutes of running it became less chilled. The A/C guy came back and worked out that there was a blockage so the system was drained of gas. The expansion valve filter was full of black bits, far more than when cleaned previously so there must have been some muck in the condenser I guess that circulated round during that initial 20 minutes of running.

So I changed the expansion valve and had it re-gassed.

But now I couldn't get the A/C to kick in, on full cold setting there is no 'go' signal to the relay.

Any ideas? The relay has power, if I bridge the relay the compressor clutch kicks in. The fuse for the climate ECU is ok.

The last thing I did when it was still working was to bridge the pressure switch to test the A/C clutch, could this have caused power surge back to the ECU ?

Stumped !

 

If you didnt change the condenser and flush out all the lines youre just gonna run more muck through the system. That muck is the from the compressor melting down and it contaminates everything so you gotta replace the condensor as you cant flush it and really should change the evaporator too. if the pressures are too low the compressor wont kick on. Not sure what happens when you jump the ac pressure sensor but thats never a good way to go.

 

Hi all, I am restarting this thread as I still haven't fixed it. The car went into storage for the winter but now it is back out it would be good to sort it out.

I am not getting the trigger signal to the relay from the ECU... so either the ECU is no good (the rest of the heating works ok) or something that passes a signal to the ECU to tell it to turn on the compressor is no good.

The compressor kicks in and the AC goes cold if I bridge the relay by the way.

Help !

 

Just for grins, is it possible the relay is bad? If the contacts are dirty, heat can build up and open the contacts.

 

Hi,

The relay and all the connectors are fine. I am just not getting a 12v feed from on the wire from the ECU.

What I haven't checked through is the output from the ECU end. It could be a broken wire to the relay.

 

Pretty sure that is green/brown wire from pin 20 on the ecu. That is the wire l switch enabled in order to disable compressor in heat mode.
Be careful when probing the pins on that ecu plug as they are very easy to short being so tight packed.

 

Right.

Are all the other climate control functions working OK?

Cheers
DD

 

On a '92 it looks like it's a green/white wire that triggers the compressor relay, according to the diagrams.

You're right about the pins. Jaguar dealer techs were issued an interesting plastic pin guard that slipped in place over the pins to prevent mishaps when testing. I had one once, now long lost. Might be worth a little Googling or asking. The guy who gave it to me (I can't remember who....maybe 18 years ago?) was a dealer tech who said he had a slew of 'em so there might be some floating around out in the world.

Cheers
DD

 

or you can slip a small silicone tube over the adjoining pins, or even over the probe itself, and then just push the probe down once the tube is safely located over the required pin.

 

Way back when l probed mine l remember using an almost stripped out old computer plug of some sort with matching pin pitch. I just kept moving it about from pin group to pin group and probing the pigtails l had left in plug.

 

Hi All,

Sorry for taking a while to respond, I haven't used the car for a while so I wasn't able to test if the climate control is working.

The climate does seem to be working ok. The hot cold valve on the bulk head is a bit sticky, tends to stick on cold rather than hot so I need to sort that out. The fans work ok and it seems to direct the air to the right places.
I also checked the green/white wire from the A/C ECU to the relay and that is fine.

So I am not sure what the issue is. I am tempted to try and borrow another ECU and see if this fixes it.

 

When I switched over to a Jensen appliance (cousin of Sanden I think) I was left with an extra wire in the loom that measured the system pressure. I believe that my Jensen (I still haven't gotten everything sorted) is made internally so that unless there is sufficient pressure it will not engage. Unless, yes, its hot wired...

What happened to the second wire to the switch on the A6 compressor after you switched up? I'm not sure, but I think when the old A6 was at sufficient pressure it grounded the pressure signal lead,,, or put it in path with the 12v - to engage???? I think (and I'm sorry for not having facts) that HVAC ECU is on the look out for that pressure signal...?

Also. Is their a separate HVAC fuse the powers the AC system on the 92? Under the dash? On mine, in the far reaches of the RH back corner, near the fire wall, behind the AC relay set up, is an old school 10amp online glass fuse that powers the AC. If blown it's a no go. Drove me nuts until I found it

 

Hi, the pressure wire on the old compressor is redundant as with the Sanderson as it has a separate pressure switch.
There is no link with this wiring to the ECU. The ecu will try and switch on the compressor by sending power down the green and white wire bit if the pressure switch is open due to low gas the compressor won't engage.

Yes there is a small 5amp blade fuse that was ok the last time I looked.

 

Ahhh,,,, I like that pressure switch set up!

Cool... Ummm, does the 92 have a temp sensor/switch threaded into the side of the fuel rail (RH)? I think the green wire travels a path thru there, as well. And,,, look for that small inline glass style fuse at the rear of the engine bay on the RH side... It's a tricky sumgun...