Hello all. Need some help please. My 84 HE has a strange a/c issue. No leaks holds gas, nice cold air, buttttt. The compressor is not cycling in and out. the climate control is not responding. I thought it had to be the ecu. Bought a new unit....no change. Any ideas would be appreciated.
Thanks
Russell.

 

Cycling is not part of the normal operational mode. If the evaporator ices up the Ranco thermostat will cut the compressor circuit until in thaws a bit....but that's it.

Could you be a bit more specific?

No gentle whirring sound when you change the temp setting?

No change in which vents the air comes out of if you call up max cooling or max heating?


Have you checked or replaced all four system fuses?


Cheers
DD

 

Your system does not have an ECU. It has an amplifier and a servo operated flap controller. These both stop working properly over 30 years or so. If you contact Gary, the very helpful guy at JagAire, in the USA, he rebuilds these units. Also he will explain how to test the servo controller, and even supply you with a manual version which cuts out loads of complications.

You have the Delanaire II system, and apart from these two things, after that it is sensors and actuators that the above things respond to. these may well go bad, but 9 times out of 10 it is one of these two.

As Doug mentioned, testing the fans are working is obviously important, too. Once working properly, the system is very powerful and reliable.

 

Nothing happens when I change temp settings. No whirring noise or change in fan speed.

No changes in the direction of air no matter the changes made. Majority of the air comes from the center vent, the other fascia vent get a little less flow.

Where are the fuses please, are they inline??

My 85 HE the compressor reacts to temp change and cycles??? So the ranco thermostat is a evaporator temp sensor ish?

Thanks Doug I'm just trying to understand this system so I can get it running as it should. I have just dismantled a 83 HE so I'm going to study the complete matrix box on the bench.

 

It shouldn't.

The designed is designed for the compressor to operate in all modes, even heating. There's no provision for it to cycle in-out according to cabin temp or temp setting on the dial

However......

If it has been changed to a pressure switch protection system....some have been over the years if the compressor has been changed....it might be cycling in-out according to system pressure


Exactly



Here's some reading that might help which includes fuse locations

https://www.jaguarforums.com/forum/x...basics-178059/

Cheers
DD

 

Yes the 85 does have a pressure switch at the low side muffler.

 

Just had a read of your A/C operations, well done very helpful.

 

Ok, checked power and fuses. Everything is getting power and fuses are good and conducting. No movement out of the servo... How hard is it to remove??? looks like a special job (lots of beer and expletives).

 

Interesting; research worthy (well, to me, at least)

I'd love to see a pic if time and opportunity permits.

The pressure switch I was referring to fits into the compressor itself

Cheers
DD

 

Glad to hear it, thanks


Cheers
DD

 

I'm confused because you said you changed the Ecu. Did you change the amplifier for the Delanair mk ii? It's a box on the left side under the foot vent. It has an inline fuse.

If you go to the JagAire site they have a test procedure to verify if the amp is getting all the right signals from the servo and sensors, in the manual for their replacement amp. The amp is the most likely failure, not the servo. I have never seen a working original amp! Do not remove the servo until you've done the tests.

Your behavior sounds like the servo has stopped at full cool position, what mine did when the amp blew.

For the a/c, What should happen is that when the right hand fan speed switch is not set to off, the compressor and the left side radiator fan come on. Does the radiator fan come on at least?

However, a bad amp will not prevent the fan and a/c from coming on.

Suggest proceeding as follows :

Check all fuses
Run the tests
If all signals correct, replace the amp.
If not, fix accordingly.

 

Yes I replaced the AMP sorry keep calling it a ecu!! I got the new amp from Elliot.
The compressor and aux fan only come on if I turn on the A/C. So the compressor runs with everthing turned off????? Really. My other xjs with perfectly working air does not run either unless I switch on the A/C

 

No, not on your '85. If the mode switch is "off' the compressor will not be powered-up.

With the mode switch in any other position the compressor will run, even when cabin heating is called for

Cheers
DD

 

When you replaced the amp, did you do the voltage checks?

 

Thats what I thought, seemed mad to have a compressor running while you are not requesting air hot or cold.

 

no. I looked on the Jagaire site couldn't find the test voltag proceedures??? has anyone got a copy??

 

Page 6 of the manual here :

https://www.jag-aire.com/ja-16-details

 

If the A/C is working and some air is being blown out of somewhere, then a duff servo is a very likely culprit. There is a potentiometer on the nd of it, and if this is not working the servo will not respond to the signals from the amp. This is why testing it as JagAire explained to me how to do, is so important.

 

Ok, have done Jagaire ohms testing

should be My results

Temp selector 0-10K 0-5.5 but lineal

Mode control defrost at 80deg ambient 37K 13.9K

Other modes 10K 5.2K

Feedback potentiometer 0 servo full heat 0.0K
2K servo full cool

Servo motor resistance Max 100K 30K good 35.1K

So out of this, nothing happening at the servo no movement I can hear. The servo potentiometer being stuck at full heat is one of the problems.

 

OK, it sounds like a rebuilt servo from JagAire might be needed and it is not expensive for what it is, 70 USD from memory. I do not know what your figures mean, but I am sure a call to JagAire would be worth it to get their advice.
Greg