XJ6 & XJ12 Series I, II & III 1968-1992

HVAC intermittent issue

 
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Old 08-05-2016, 04:37 AM
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Default HVAC intermittent issue

We have the following phenomenon in the XJ12C.

It has become increasingly more difficult to get the system to turn on. "Turning on" means moving the right hand switch from "off" to anything, ie low, auto, high, def.

When it doesn't turn on properly, the fans dont run, the A/C comp doesn't run, but the vacuum system seems active as we can hear flaps moving. I didnt move the left hand control to see if in the fail state the servos are actually responding or not, but I can do that experiment if it is going to help the diagnosis.

The only way to get it to work is to constantly jiggle the right hand switch from off to low until eventually (which can mean 30 minutes) it fires into life and works perfectly. Usually it keeps working until you shut the car off, whereupon at next start up you have the same battle but sometimes it will just die when the car is running.

After much reading of posts on here, my current working theory is I have an issue with at least one of the micro switches in the right hand control switch. If so, my first attempt at a fix would be to tighten up the 2 screws that are typicaly found loose, as Grant suggested.

I'd be glad to get feedback on if you think I'm on the right path here.
 
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Old 08-05-2016, 05:28 AM
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On my fleet of Jags with this system, and there have been many, the fiddle factor with that switch is 90% the switchpack is loose.

Take a day, lubricate yourself, JD or similar, and go for it. It is a mongrel task, fiddly as hell, and the build reasonong behind this system will be questioned/challenged many times.

The first one took me HOURS, then I got better at it.

If that fails to wake it up, then the list is LONG.

I have never had an amp failure, or any of the things on that LONG list, but the switch pack security has been the main culprit for me.

I know very well the "off to lo to off to lo........." fiddle very well.
 
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Old 08-05-2016, 09:19 AM
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@Grant

Very good sir, we will try that this weekend.

I am doing an audio install on this car so while I have the radio out I will do some of that work to at least make myself feel better
 
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Old 08-07-2016, 09:53 PM
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@Grant

Mission accomplished. I ended up taking the center console out so I could get the whole switch out while still connected to the metal panel it lives on. I was doing other stuff (stereo install, LED conversion for the heater controls, 2 stealth water temp gauges inside one of the ashtrays) so taking the center console out helped a lot for all that anyway. It was one of the microswitches that had failed. Interestingly, it looks like someone had already been in and replaced the switch once, because the switch that engages the A/C comp and fan circuit was different from the other 3........ I replaced them all. The original set up had 2x 2 way and 2x 3 way switches, so I just bought all 3 way switches and only used the terminals I needed. For the folks in the US, this is the switch I used, available at Fry's Electronics. You need 4 of them for the full system.

FRYS.com*|*PHILMORE

10 dollars and 6 hours..... thankfully I'm not charging myself labor
 

Last edited by Sarc; 08-07-2016 at 09:56 PM.
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Old 08-07-2016, 10:56 PM
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Six hours to fix a cranky Delanair climate control? That's a home run in my book

Cheers
DD
 
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Old 08-08-2016, 01:27 PM
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Originally Posted by Doug View Post
Six hours to fix a cranky Delanair climate control? That's a home run in my book

Cheers
DD
It would have been a lot more if not for the expert guidance we got from the forums !
 
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Old 08-09-2016, 02:56 AM
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Well done.

Doug is spot on, that time would damn near be a record.

Fry's still around?????.

I spend HOURS in there when in Vegas, spouse goes to Dillards.
 
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Old 08-10-2016, 10:43 PM
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Yes, Fry's still open. Yes, I can spend hours in the place too !

Now, only if you are really bored.......... watch this.

https://vimeo.com/178420287

All mistakes are solely my own :-)
 

Last edited by Sarc; 08-10-2016 at 10:56 PM.
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Old 04-29-2017, 09:18 AM
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I'm having the EXACT same problem with fiddling with the switch to get it to work. MANY THANKS for this thread. I watched the video - outstanding. Now I know what I'm getting into. And I ordered 4 micro switches from FRYS. You guys are the greatest. I hope I can give back at some point.


Bill
 
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Old 04-29-2017, 09:51 AM
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What did you order for YOU, to calm the nerves, haha.
 
 
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