My heated seats did not work, although dashboard buttons worked and relays under the seats were clicking.


Today I decided to trace the problem and first I wanted to see if relay under passenger seat has power coming to it. So after doing some acrobatics I was able to prove that one of the switchable pins has power coming to it (the one that is aligned the same way as the two connected to the coil). That tells me that I need to look into seat's heating element or seat thermo-relay)


However, now when I press heat button for either passenger or driver seat - both lamps light up (like if I pressed both buttons) and relays under seat do not click anymore! I guess I broke something. All I did was connecting a 1w test lamp between relay socket pins and ground.


Does anyone know what causes both lamps to go on when I press one button? Hope it is a known problem.


Thank you.

 

Do a computer reset. Disconnect the battery cables and touch them together.

 

I can't imagine that you broke them just testing them. I thought the heated seats in my XJR did not work, but found out that they did, I just had to wait until it got cold enough, which is tough to do regularly in S. Cal.

Apparently Jaguar heated seats do not work the same as Saab, Volvo, Land Rover or BMW seats.

 

Thank you Lear45. Will try computer reset. But first I am thinking to get the seat out and take a good look at all connection. Just bought torx 50 socket for that.


Thank you smtguy. I got car this winter and seats did not work when it was cold. I have detached unheated garage, so there is definitely a problem . There are good guides here on the subject, so I will follow them. Now I know that power was supplied to the seat, so the problem is in the heating element or seat temp sensor.

 

Do a search for a thread called "seat heat solved" under my username. It will help with the thermostat issue, anyway.

 

Some progress today...

To solve the problem with both lamps switching on/off together I had to replace fuse 16 in right side fuse box, behind heel board, 25A fuse in lower row, last toward the center of the car. No need to do computer reset.

Next I got seat out and got my hands on thermostats. Both thermostats were open so I blamed them (though it is warm outside and perhaps they should be open at this temperature). I took them out and soldered the wires together. There is a yellow two-wire connector that connects to bottom heat element - after soldering thermostat wires it now has low resistance, less than 1 ohm. - good!

Connected the seat back, clicked heat button, and.... nothing! So now problem is either in the back heating element (does it have a thermostat too?), or in one of those control boxes under the seat, or some wires are bad. To be continued after my knuckles heal :-) ...


If anyone has any suggestions or seat heaters related electrical diagram for xj8 2003 - it would be very helpful ( I see 2001 and 2004 out there but they are different).

 

And here is the picture of my passenger heated seat problem...

If anyone knows a reasonably priced replacement please let me know.
I wish designers did not connect heating elements is series... at least one would be still working and I would need 12v rated replacement. Not even sure what to look for now( 6volt rated pad I guess...), I might just replace both pads and wire them in parallel.