I have searched through many postings here and on other Jag slave sites and I think I have narrowed my problem of my '83 XJS. My climate control is wonky. I, like others, will be enjoying cool air conditioning on a nice summer day and then the servos start doing their thing and then I have hot air roasting my feet. The opposite occasionally occurs but only rarely. Staying in the A/C mode is the biggest challenge. I’ve checked all the vacuum lines and they are all intact. The servos are directing the air and shutting off the hot coolant flow in a very coordinated manner, just at the wrong times. I never get air out of the foot and center vents at the same time or any other combination to suggest a servo problem. From my research I think that the amplifier is the most likely culprit, with the temperature sensors being a distant second. I did confirm that the under lip air sensor intake by the glove box was still hooked up and the wires were attached. I actually went through the nut roll of removing the amplifier, the placement of which had to have been designed by a sadistic psychiatrist and a contortionist as part of a test to assess dexterity, ingenuity, and patience in patients with OCD. I’m not sure I’ll be able to get it all back together but it’s out now. Does anyone know of a way to test the unit to conclusively determine if it is the actual problem. If I had another XJS I would just do a plug and play without a complete installation, but I would have to do it on the side of the road because my wife would likely kick me out of the house if I purchased another one.
Any help and instruction would be greatly appreciated.
Is there a good place to get a replacement without rendering my sterile?
Almost-lost,
Excellent job of diagnostics thus far. There are two likely points of failure…the feedback potentiometer or the amplifier.
I can test your amplifier free of charge on my teat rig…you pay postage.
But the general rule of thumb…is if everything else tests ok…then the amplifier is the only possible cause…without a test rig…there is no direct way of testing the amp.
The feedback pot sends voltage signals via a potentiometer to tell the amp that the system is balanced. If the wire wound pot is dirty or broken…then the amp gets the wrong signal an usually defaults to the extreme conditions of full heat or full cold.
You can test the feedback pot from the amplifier harness connector. A digital voltmeter and 9 volt ( or other 12 volt power source with probes) battery with leads will be necessary.
On female side of plug …Connect voltmeter (set to ohms) to orange and green …now apply + to red and - to purple. Listen for servo to move to limit switch. Observe reading…then observe Ohm values as you reverse polarity on red purple and drive servo to other limit. You should find a smooth change in value ranging from 0-300 ohms on one end to 2000-2200 (2- 2.2K Ohms) at the other. If this test good. Your problem is a faulty amplifier.
Cheers
Gary
I went through several rounds of mine working, not working, working again. This was with a brand new amplifier from JagAire.
The problem in the end was bad connections in the multiplugs. There are two, one on the left near the amp, and one on the right near the servo unit.
The servo unit multiplug was the cause of my problems so I simply cut it out, joining the wires with heat shrink butt crimps. It’s worked great ever since. I did a multiplugectomy on the other side too, just to be sure.
The confusing part is that everything checks out perfectly with a meter, and then works intermittently when you put the connectors back together. Every time you troubleshoot with the meter, the connections get worse - I suspect the meter leads tend to open up the sockets in the multiplugs.
Thanks for the input. I think that the first thing is to make sure the amplifier is working. If you are willing to test it just give me an address and I will send it to you. I understand that you are Jag-Aire so I would hope that you would be able to help me out with this. Obviously a new amp is a pricey fix so making sure that’s the problem is the first order of business.
Thanks,
Kyle Colvin
Thanks for the input. I am hoping that there is just one issue with the climate control and not a combination that will leave me scratching my head until my hair falls out. I will keep in mind the problems you had with the connectors. I think that I will first send my amp to Jag-Aire to get it tested since that seems to be the frequent offender.
Kyle
You know, you can just hotwire those red and purple wires, or better yet install a momentary switch, to help confirm that everything else besides the amplifier is working OK. It’ll also help make the car livable while you’re waiting to get the amp fixed.
Do you mean jump a 12v hot lead to the harness red or purple leads while leaving the remainder detached? This should yield full cold or hot, respectively? Isn’t this the cheap Jag-Aire solution forgoing any temperature control?
The Red and Purple wires basically feed the servo motor. By changing their polarity you move the servo to one direction or the other, i.e. colder or warmer.
The Jag-Aire scheme is a momentary switch that does exactly that, so you can stop the servo at any position / temp setting.
It just forgoes the Automatic control i.e. the amplifier.
Have your Amp tested and if it’s bad I would get a new one if i was you, Jag-Aire also has them.
Best,
Aristides