Remote fobs only work with boot open!
 

1998 XK8 coupe owner here. Had my key fobs refurbished and they work perfectly - but only if the boot open is open (I discovered this by accident!). With the boot closed, I have to hold them about 5cm from the top of the rear window to get any kind of response. Live in Sweden, where it's fair to say knowledge of these cars is limited, so would really appreciate any tips.

Have you tried new batteries in the fobs? I think your fob takes two batteries rather than one, so check that as well. Motorcarman posted this photo showing which fob is which:-

https://solnerja.com/wp-content/uplo...8-key-fobs.jpg

Thanks, yeah fobs are refurbished with new batteries. As I mentioned, the range is fine as long as the boot is open!

Are you 100% sure that both the refurbished fobs have been fitted with two CR2016 batteries in each? It is very common for people to use one CR2032 as the size is the same.

Try this ..... stand away from the car and push the fob gently against the side of your head and then operate the button. Does this improve the range?

Richard

I am 100% sure there is no issue with the fobs. Thanks for the suggestion though

Personally, I would open one to check as it only takes 5 seconds.

Try the "head holding" thing.

Richard

If you're still having issues after the above suggestions, check that the connector to the antenna in the rear window hasn't detached from the stud on the glass.

Also check out this thread from simon3166 for possible causes:
https://www.jaguarforums.com/forum/x...4/#post1721719

Head trick, no difference. Yes the connector is attached and can't see any obvious problems with the connections to/from the SLM, but it feels like you're on the right track. Surely has to be something to do with the antenna/receiver given how opening the boot seems to affect things?

Well remembered - your memory is better than mine. That thread has the full details of a fix where three connections are resoldered on the RF board in the SLM:-

https://solnerja.com/wp-content/uplo...702_131858.jpg

To the OP - after checking your remote's batteries, I would check the wire that goes to the aerial. Disconnect the end at the SLM and using continuity on your multimeter check that you have a very low resistance to the aerial and ground, in case the cable is broken. After that it looks like you'll have to open up the SLM.

Thanks, I'll try and get someone with electrical knowledge and tools to tackle the SLM (that's not me). In the meantime I'd be really interested to know why opening the boot fixes reception, in case anyone can offer an explanation?

Having the boot lid open removes some of the body metal which normally shields the SLM, which is itself housed in a plastic box that doesn't particularly impede the radio signal. Does sound like there's an issue with the antenna or its coax feed.

Curious:- what range can you get with the lid open?

Do the trunk lights work ? Is it in valet mode ?

Range with boot open, a couple of metres at least. 10cm when closed!

Boot lights work fine. No, not in valet mode.

OK - you should get at least 10-15 metres when it's working properly.

Definitely check the aerial before opening the module - maybe even try a new aerial. Opening modules and re-soldering is always a last resort.

BTW valet mode doesn't affect the operation of the remotes. The idea is you don't give the valet the remote, just the green key.

I've done a basic check of cable going into SLM and stud contact at top of rear windscreen. What else can I check re aerial specifically (if anything)?

You could try improvising an antenna with a length of thin wire connected to the plug on the SLM, which looks like this (at least, on my 98):

https://www.jaguarforums.com/forum/x...1/#post1591650

Problem is that the battery blocks access, either that or you need to pull the trunk fusebox :(