Greetings!

I've Googled but not found a lot of helpful advice. 2000 XK8. When I press the dash button for either seat I hear a click like a relay inside the dash, and the switch light comes on. But neither seat heats.

Can somebody point me in the right direction? Which fuse(s) may be involved? Are there other relays involved?

BTW, all the other functions of the seats work - recline, fore/aft, lumbar on driver's side (never checked passenger side. Does it have lumbar?)

Thanks!!

 

If the other seat functions are working OK then you can discount the power feed to the seat modules

Check for power to the seat heaters - it's the orange wire out of each module.

Odd for both to go out - did they ever work?

Bottom of the checklist would be that the modules might both have been replaced. Seat heaters were an option, and the modules needed to be programmed to suit. I don't think that shows up on the VCATS reference.

The EG shows lumbar on both seats, but IDK if it was an option (FWIW, mine has both).

 

Thanks for the reply!

I have no idea if they ever worked. I rescued this car from sitting in a garage for eight years, and serious neglect prior to that. The thing has only been roadworthy for a couple of months. I had never tried the seats until a recent cold evening. As they were optional, did cars without the option have different buttons where the seat heat buttons are now?

I'll check for power at the orange wire and go from there.

 

AFAIK, just blanks where the seat heat switches would be fitted. Mine is similar to this:



I originally thought they were a bit gimmicky, but Mrs. H's X5 has them and I'm converted.

Does it really get that cold in CA?

 

Thanks for the pic. That helps a lot. Is there also a fuse I can check?

I never thought much of them either. Until I got them working on my E39 project (blown fuse). I used them on a chilly night and now I'm a believer!

Southern California certainly doesn't get nearly as cold as other places I've lived. But when the temps dip into the low 50s the leather gets a bit chilly and is a shock to my delicate hindquarters! I know, I know. First world problems!

 

LOL

I've rechecked the EG and I can only find a single feed to each module. You can try F1 (20A) in each side fascia fusebox, but I doubt they're blown else the other seat functions would also be out.

The under-seat wiring is subject to some flexing with seat movement so it's worth checking for breaks.

 

Thanks! Your assistance is much appreciated!

I think I was premature in my diagnosis. This being my first Jag, I had nothing with which to compare. My BMWs have 3-position heaters. The first will singe the hair off of your butt. In all settings the seat and the lumbar region get warm.

Last night I headed to the market, and turned on the seat heat just to see. It took a few minutes, but I noticed a definite warming in the seat bottom. It was very "mild" and the thermostat seemed to have a relatively low temp setting. Also, the seat back didn't seem to heat at all, and maybe they don't in the Jag. But, the seat heater does appear to be working. I suppose I didn't give it enough time when I first tested them. I assumed they'd heat up within a minute.

One more item to scratch off the list. Yay.

 

The backs do heat in my 2002 XKR

 

+1

That turned out to be the cause on my 2005 XK8 4.2-S.

Graham

 

Yes, seat and back are both heated: the elements are wired in series so it's all or nothing.

 

Is there an affordable code reader that can read the seat module?

 

Sigh. I spoke too soon. Cold night tonight, jumped in, turned on the heaters and drove for 20 minutes. Nuttin'

Is there a way to determine if my modules have been replaced by looking at them?

 

Only if the part numbers differ from what's on your VCATS label, AFAIK.

Have you managed to establish whether the modules output B+ on the orange wire in response to the seat heater button being pressed?

 

I'll check the numbers when I have some time. I've been swamped finishing an N54 build for a friend's GF's E90. I'll post results here. And thanks for your guidance!

 

I have a similar problem. Passenger seat heater works fine, drivers side…turn switch on, dash light on but no heat in seat. To test circuits, seat heat will only turn on with engine running, will not turn on with key on so have to have engine running to test circuits and too cold here to do that in garage. Is there a code reader that will diagnose seat module?

 

In general most heated seat problems AFAIK are broken (worn) heat elements in the seat requiring a cover removal. They can be repaired as I found on Youtube. It's amazing what fix it things you can find there. The heat in these cars is not real warm but makes a difference. I believe it to be controlled by ambient temp also it would have to be colder outside for it to be more effective.
The best heated seats I had encountered are in any GMC truck I have owned, wowsa!!! Talk about toasting your buns. TM

 

There are some Bnnnn codes relating to the seat modules in the latest (2003) DTC list I have, but these won't necessarily appear on earlier models. You would likely need the Jaguar diagnostics (or at least an advanced code reader). Nothing in that list related to seat heaters, tho'

You could try swopping the seat control modules over to see if the fault also moves across.

 

They don't in my '04, only the bottoms.

 

Both heat in my 2002 XKR, but the seat bottom seems to get hotter than the back. Could be just a subjective thing.

Z