XJ6 Electrics acting up

geekman · 10 Oct 2013 at 18:20

Some very strange electrical issues have started appearing on my 2003 XJ6 and I'm not sure what the cause might be.

The interior light stays half-on all the time, the electric window switches don't work (but the windows go up and down fine with the key) and my auto headlights stay on even when it's light.

These issues started a couple of days ago and they're intermittent - earlier today the window switches worked fine and now they don't.

I've checked all the fuses and they're fine, so I'm thinking it's likely to be the battery or perhaps the alternator. Does anyone have any opinions on this?

Oh, and if you agree it's probably the battery, anyone got any ECP discount codes?

paradigm · 10 Oct 2013 at 18:24

The first two suggest to me that there is a problem with your door wiring.

The auto-headlight one however, no idea!

Firestar_3x · 10 Oct 2013 at 18:35

Could be a bad earth.

p1RATE · 10 Oct 2013 at 21:39

Firestar_3x said:
Could be a bad earth.

I would also be thinking this.

geekman · 10 Oct 2013 at 22:31

Looking on Jaguar forums they seem to be saying either battery or earth - more likely to be the earthing points apparantly. I recently removed the glovebox in order to replace a broken heater resistor but I don't think there are any earths there, so that's probably just coincidence.

Just been for a quick drive and none of the instruments illuminate apart from the speedo cluster - very annoying!

Rilot · 11 Oct 2013 at 09:59

My first thought would be a bad battery. Jags and Rangerovers go spaz when the battery voltage drops below a certain level. Everything can appear to be fine and then suddenly a bunch of unrelated faults will appear.

Swap the battery for a new one and see where you get.

geekman · 11 Oct 2013 at 13:51

Rilot said:
My first thought would be a bad battery. Jags and Rangerovers go spaz when the battery voltage drops below a certain level. Everything can appear to be fine and then suddenly a bunch of unrelated faults will appear.

Swap the battery for a new one and see where you get.

I think that'll be my first course of action. Having done some more investigation, these issues only occur when the lights are on. Does that change anything?

Howard · 11 Oct 2013 at 14:56

Rilot said:
My first thought would be a bad battery. Jags and Rangerovers go spaz when the battery voltage drops below a certain level. Everything can appear to be fine and then suddenly a bunch of unrelated faults will appear.

Swap the battery for a new one and see where you get.

I was going to say the same. It isn't seemingly limited to Jags/LRs either; many "higher end" cars with very complex electronics appear to get upset when the voltage drops.

It's possible that the additional current draw when the lights are on is exacerbating the issue. Have you tested it with the lights on and off without the engine running, with the same effect?

Jez · 11 Oct 2013 at 15:25

Rilot said:
My first thought would be a bad battery. Jags and Rangerovers go spaz when the battery voltage drops below a certain level. Everything can appear to be fine and then suddenly a bunch of unrelated faults will appear.

Swap the battery for a new one and see where you get.

Same with Mercs. Both my SL and old S go haywire if the battery got too low. Ive started leaving my SL on a CTEK after a while as it drains itself fairly fast.

pepsilol · 11 Oct 2013 at 15:31

Weathers gotten wetter recently.

Water leaking in somewhere?

geekman · 12 Oct 2013 at 13:08

pepsilol said:
Weathers gotten wetter recently.

Water leaking in somewhere?

Possibly, but IIRC these issues started just before the weather got wet.

The EML came on last night on my way home - I had a look at the earth points this morning and gave them a clean although they were pretty clean anyway. I also bought a new battery as the old one had "2008" written on it.

Unfortunately, neither seems to have solved the issue. Someone on another forum suggested that it could be because I took the glovebox apart last week to fix the heater resistor, but as far as I know there aren't any earths or anything like that in there.

Really confused by this tbh

Bear · 12 Oct 2013 at 18:45

The next step I would investigate would be to take the glove box apart and pull the heater resistor pack and see if it goes away, just to eliminate it. You never know, you may have upset something in the process in fitting it.

It probably hasn't got anything to do with it but I find it is always best to start from a known point.

geekman · 12 Oct 2013 at 19:19

Bear said:
The next step I would investigate would be to take the glove box apart and pull the heater resistor pack and see if it goes away, just to eliminate it. You never know, you may have upset something in the process in fitting it.

It probably hasn't got anything to do with it but I find it is always best to start from a known point.

Yes, that is the next step. I'm considering getting a jag specialist to look at it as it was an absolute **** of a job getting the glovebox out and I'm not sure I can face doing it again, especially if that doesn't solve the issue.

pepsilol · 12 Oct 2013 at 22:01

Short/Open Circuit sniffer?

geekman · 19 Oct 2013 at 15:13

Just got it back from the garage and it's fixed. They said they'd call me if the bill came to over £500, and it was rather conveniently £499.99 :rolleyes:

Fault was a bad ground in the body control module apparently, so not something I'd have been able to sort out myself. Annoying, but just one of those things I guess.