1998 VDP; rear seat heater electrical gremlins ....
 

o, I am literally at the very last point of my "to do" list of my Vanden Plas, and I am stuck ... I hope someone can help with some credible advice here.

I have the interior back in the car, the front seats are perfectly working, including the freshly installed seat heaters.

However, the rear seat heaters are giving me some problems.
Basically they don't work, neither will the switch do anything (not even activating the red LED in it).

I have worked my way through the various electric supplies and components, and the following is working (same for left and right):

- Main power supply 64 + 65 = OK
- Control power supply 25 + 26 = OK
- If I install the timer relay in the socket, I also have power at the U (blue) output from the relay (is that correct?)
- If I manually override the timer relay, I have power on the red wire, the heater is powered, and the red light in the switch goes on

Above tells me (but maybe I am wrong) that all basics are there, but that the switch is not activating the relay for some reason.
I have swapped left and right relay, but no difference.

I would like to confirm the working of the relay before blaming the switch (which is harder to check now it is installed in the console).
My question is, how can I test the timer relay (never handled one before) as stand alone, or as installed in the system?

Note: the switch is a trigger switch, one push is on, returning to neutral, the next push is off.

https://cimg7.ibsrv.net/gimg/www.jag...127b0d64fc.png

Never mind, traced the problem to a tiny part of the micro switch inside the heater switches.

Those micro switches are internally of the same design as the key FOB, with a small carbon surface connecting the contacts if pushed.
And after 20 years the carbon is worn off, and the contacts polluted.
Enough to prevent the switch from working under load, but not enough to block it all, so while testing it shows fine ... :icon_cry:

Solved it as I did my key FOB, glued a minuscule piece of alloy kitchen folie on the inside, replacing the carbon surface.
Let dry for some hours, and all is working as it did in 1998 .... heated seats front and rear.

https://cimg7.ibsrv.net/gimg/www.jag...7c92d792d1.jpg

Never mind! fixed :)

Exact!
And you know what?
My To Do list is empty for this car ..... no excuses not to re-start on my XJ-S any more ...