No voltage to A/C compressor clutch
 

Hi XJS guys,
Hope I am in the right place with this problem. I bought this car several weeks ago and inherited this problem. No voltage to the a/c clutch in any mode. If you hot wire the clutch, it works fine. The system is fully charged and all fuses and the relay for the clutch are fine. I know there is a dual pressure switch which I am suspicious of but can't seem to find it. With the system fully charged but not running, should the pressure switch be closed? Does it open only at very high or very low pressures? Also, isn't there a sensor in the evaporator coil which cycles the clutch to keep the coil from freezing up? Any of you guys experienced a similar problem?
Please help if you can.
Many thanks,

Spillwaybob
'94 XJS 6-litre, Stock

Hey Bob,
See if this helps.

So assuming you have engine running and the interior fan set to at least position 1, check pin 86 of the clutch relay. When the A/C button on the climate control panel is off, you should be open circuit at the pin. When you push the switch on, you should have 12V at the switch.

The dual pressure switch should be closed when pressure is between 29-392 PSI. Also there is a coolant temp switch between the pressure switch and ground which should be closed unless coolant temp is above 250F.

Also, check the ground connector which is behind the right headlamp, these often get corroded and can give dodgy signals.

Cheers,

Allan

Bob,

I'm not sure if you have an R12 or R134A system, most 94's are the latter.

Jim, I think that is the diagram for an older model, here is the one for a 94 with R134A :)

Attachment 49111

Cheers,

Allan

HeyJim,
Thanks, but I can't open the attachment. Guess my computer does not have that program. Is there any other way you can send it?
Thanks,
Bob

Bob,

See post #4 above :)

Cheers,

Allan

Hi Bob,
Click on it again and then look just above your start menu button. There may be a tab there to open it.

If not then you can download the complete elec diagram for your car, for free,
here //www.captainjaguarscathouse.com/Electrical_Reference.htm

Allan, yes it is a 134A system. Got the attachment fine and printed it out. This will help me for sure.
Thanks,
Bob

Glad you got the right stuff Bob, hope you can get it fixed without too much trouble.

Allan,
Wow!! you hit the nail on the head! Pin 86 on the clutch relay checked out as you said it should. The large multi-wire ground on the top of the right head lite was only snug so I loosened it and tightened it down. Voila, the clutch engages now without the hot wire. Realy glad that this problem is fixed.
One more problem with this unit is there is no air coming out of the right dash vent in any mode. Low air volume on the Left side and strong volume on the center. Both blower motors are working and it appears to be a problem with the vacuum acuator for the right side. Could this be the ACCOM? (A/C Control Module) The manual says it's located on the right side of t he heater core but where is that??
Thanks again Allan for helping me get my car working right.
Bob
'94 XJS V12 stock

Hi Bob

Glad it worked out and was an easy and cheap fix!! :)

As for the A/C issue, welcome to the magical mystery tour of the XJS climate control system!! :D

I haven't had the pleasure of playing around much with mine yet ;) perhaps you have a flap that is stuck? Or the center vent solenoid is acting up? Of course it might be more basic like a physical blockage.

I'm not sure that there is a right and left side actuator? There is an upper and lower.

The A/CCOM is under the dash on the right side.

Cheers,

Allan

'94 XJS V12 Climate control system
 

Hi Allan & all who helped.

I am ashamed to tell you guys what the problem was with no air at the rt. fascia outlet-----THE FREAKIN FLAP WAS CLOSED OFF!!!! That's OK, go ahead and laugh!
The plastic wheel that controls the flap is so well disguised in the grill that I didn't see it. This is one of the signs of diminished brain power as you age!
OK, I put my gauges on the system and let it stabilize and the low readings indicated low charge to I added almost 2 cans and now readings are about 30psi low side and 275 high side. This was in 92 F deg. high humidity and squirrel cage fan in front of radiator. A/C blower on medium speed, temp. control on cold and the best temp reading I could get was 50 F deg. at center fascia outlet. This definitely won't get it in this climate. What I don't know is whether the recirculate door was open or closed. If the unit was sucking 92 deg. air into the evaporator, then 50 deg. coming out is not too bad. But if it was on recirculate, then this is very poor performance. I have read the books several times and can't figure out how the system decided whether it is going to recirculate or what?? Does any one know the answer to this. I don't understand why Jaguar would take this choice away from the owner. My '01 XJ8 had a far superior system than this car does. Do I have a problem or is this something I have to live with??? Thanks to all of you that are putting up with me.
Bob (HOT IN NEW ORLEANS)
'94 xjs v12 Coupe, Stock.

Hi Bob,
Thanks for the giggle.
With a fully functioning system you should be looking at around 6.7c or 44F at the fascia panel, so you are not far off with 50F at your outside temp.

I don't know if your car has one, but it may be worth checking to see if it has a pollen filter on the air inlet side to the evaporator.

With the recirc on, the inside should get cooler, don't forget, it is a steel box without a great deal of insulation so the in car temp will only come down so far.

Bob,

Glad you are finding easy solutions!! :) My understanding is that the system only goes into recirc mode when you press the recirc button.

There is no Pollen filter that I know of in the system.

If you are just idling, at your temps the system probably won't be able to keep up after a while. Once on the move you should be good. Perhaps look into increasing fan throughput?

Also you might want to check the condenser and make sure the fins are not blocked or gunked up. Maybe also check the compressor clutch to make sure it's not slipping.

Cheers,

Allan

Allan,
Attachment 49250

Allan,
My A/C system does not have a recirc. button. See attachment and click twice to enlarge. I checked today to see if I could make it go into the recirc mode and I found that in the A/C mode, regardless of where you put the temp. and blower controls that the system is using outside air. That is my problem. You can't cool 95F deg. air to 40F deg. with this unit. I will study the shop manual tomorrow and see if I can find out if and when the system is supposed to recirculate the air when A/C is on.
No problem with A/C clutch slipping and condensor coil is clean. If this was blocked, the high side pressure would have been very high.
The BIG question is: WHY DID JAGUAR REMOVE THE OPTION TO RECIRCULATE THE A/C AIR FROM THE OWNER???
Will let you guys know what I find in the shop manual tomorrow.
Thanks again for your interest,
Bob
'94 XJSV12 Coupe

Bob,

That's very strange, is your car a very early MY94? I thought all 94's had changed the aircon controls to include a recirc.

Here is a photo of my unit, as you can see the recirc button is right next to the AC button.

When was your car built?

Attachment 49255

Cheers,

Allan

50 at the duct with 92 OAT with a "fan in front of rad" and idle speed is what I would call "normal" I'm sure you'll pull that duct temp down to 46 or so at speed which is plenty cool for R134 and 92 OAT. 2 cans added is a lot and would mean there was barely enough in the system before to get the compressor to kick on in the first place. IIRC that whole system only takes 34 to 36 oz's.

Allan,

The original MSRP window sticker does not have any dates on it, but the port of entry was Baltimore. The bill of sale to the original owner was dated Feb. 12, 1994 is from the Jaguar dealer in Madison, N.J. The car was manufactured in 10/93 which makes it an early '94.
When was your car manufactured?

Bob

Hi JTsmks,
I think you may have missed the point a little. The point is that if you are sucking 90+deg hot air into the evaporator coil, you're not going to get comfortable duct temp. inside the car. 46F deg. is not acceptable. If I had the option to recirculate the air inside the car, then I know I could get near 40F deg. coming out of the ducts. Jaguar must have found this out themselves because the later '94's had a recirculate button------see Allan's letter above yours.
Thanks for your input
Bob
'94XJS V12 coupe, stock

Bob,

My car was built 3/94. I'm very surprised that your car has the older control system. I thought they changed it in tandem with going to R134A refrigerant. Although it's not unusual for Jag to slowly roll out changes during a MY :(

The only other thing is to be careful how much refrigerant you put into the system, I know that if you have too much, cooling efficiency is deminished.

I live in NC so 92F temps and high humidity are not uncommon. My A/C works fine in normal (non-recirc) mode which I almost never use. However, as I mentioned above if I'm just idling or creeping in traffic for 20-30 mins or so the cooling system can't keep up. As soon as I start moving at normal speed normal service resumes.

One other thought is the receiver/dryer? Maybe the filter is blocked or the desiccant has lost some of it's effectiveness?

Cheers,

Allan