Instrument lights out

I have just changed the battery on my P38 diesel, and the dash lights & clock light won't come on when I turn the lights on. I have checked the fuses, the radio and clock still works.
Any ideas?

Hold the dimmer switch on top of the indicator stalk to the right.

wammers said:

Hold the dimmer switch on top of the indicator stalk to the right.

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I have tried that, or do you have to hold it for 30 seconds or so? I thought that was for the headlight adjustment?

Have you tried it with the ignition on and lights on?

Gaz5535 said:

I have tried that, or do you have to hold it for 30 seconds or so? I thought that was for the headlight adjustment?

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Switch the lights on and move control to left to dim dash lamps and to right to brighten them.

Well that's obviously stopped working then, as it doesn't do anything. Weird how it everything was fine before I changed the battery?

Doo said:

Have you tried it with the ignition on and lights on?

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Yes, I have tried all permutations, still no joy!

My next port of call would be to try the old trick of undoing the battery, neg - and leave it a few minutes before reconnecting. It may or may not work. If not, check the BECM plugs aren't compromised. Usually it's damp off the carpet that does it. Undo battery, leave a few minutes then pull each plug from the BECM (it's under the drivers seat BTW). Cheack for signs of corrosion, but use a strong torch because it may be hard to see. Eventually found this to be the cause of my drivers window not working. Cleaned it up with a mouse tail file, some contact cleaner (both available at Maplin) and it's been fine ever since..... Unless you count the rear drivers side window But since I never use it I haven't got around to dealing with it yet

These old girls are tempraMENTAL and sometimes they need a tickle in the right place, ooh err

Ok, discovered your problem this afternoon... It'll be the ignition barrel at fault!

I left my sidelights on today, came back to the car & opened the door, fitted the key into the ign before I get my arse in, then crutches... I digress, I discovered the dash lights up when the key is inserted!

So I imagine the fault lies somewhere along there.

One of the guys will figure it out, but I should imagine the key might need to be synced with the BECM to tell the dash lights to go on or some such...

Doo said:

My next port of call would be to try the old trick of undoing the battery, neg - and leave it a few minutes before reconnecting. It may or may not work. If not, check the BECM plugs aren't compromised. Usually it's damp off the carpet that does it. Undo battery, leave a few minutes then pull each plug from the BECM (it's under the drivers seat BTW). Cheack for signs of corrosion, but use a strong torch because it may be hard to see. Eventually found this to be the cause of my drivers window not working. Cleaned it up with a mouse tail file, some contact cleaner (both available at Maplin) and it's been fine ever since..... Unless you count the rear drivers side window But since I never use it I haven't got around to dealing with it yet

These old girls are tempraMENTAL and sometimes they need a tickle in the right place, ooh err

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Hello Doo, I was thinking of disconnecting the battery, I will give that a try. Btw,what is a BECM? I know there is a fuse box under the drivers seat.
Gary

Gaz5535 said:

Hello Doo, I was thinking of disconnecting the battery, I will give that a try. Btw,what is a BECM? I know there is a fuse box under the drivers seat.
Gary

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That "fuse box" under the drivers seat is the BECM or Body Electronic Control Module. It's a serial bus controller that can communicate to various independent stations using something similar to digital serial comms. It cuts down on the sheer amount of wires needed. If you imagine it will have a positive & negative power feed and some wires from the BECM that can communicate many different signals via very few wires. It's an old system, but still pretty clever by today's standards.

Like any electrical system, it relies on clean contacts and uninterrupted feeds. So if you have a damp patch on a plug, it can cause some corrosion and high resistance which will create all manner of hassle. Most of the BECM problems are ultimately caused by poor connections, short circuits and even just a bad battery earth!

The problem is there are so many different possibilities for failure from the BECM connector, ignition switch, dimmer on the indicator and even the dash connections...

Hello Doo, thank you for your reply. I will have a look later when it warms up a bit. Are there any specific plugs that I should look for? As far as I know the switch on the top of the indicator stalk had never worked, I always assumed that it was a head light dimmer. I did change the stalk for a good secondition hand one last year because it had issues with dipping from main beam whilst indicating.
Gary

Yeahh, thanks Doo. I disconnected the earth for a whilst & guess what... The dash lights wor, along with the CD player, which had gone on the blink ayr the same time.
I am probably going to regret saying this, but the old girl has some funny little quarks, that you guys luckily seem took have a vast knowledge of. Most of problems are simple inexpensive fixes.

That's excellent Glad it's all working now

If you think about it a bit like a computer. I've seen me losing power (battery run out on laptop for instance) and rebooting brings all manner of silly gremlins. So, reboot again and all is well Cars are a bit like that. My 2004 XK8 needs the full power from the battery or all strange happenings occur It purely because most systems are voltage critical and on a car like the P38, the BECM does NOT like being disconnected or it may "forget" a few chores it must carry out

Anyway, keep on truckin and Happy New Year

Doo said:

That's excellent Glad it's all working now

If you think about it a bit like a computer. I've seen me losing power (battery run out on laptop for instance) and rebooting brings all manner of silly gremlins. So, reboot again and all is well Cars are a bit like that. My 2004 XK8 needs the full power from the battery or all strange happenings occur It purely because most systems are voltage critical and on a car like the P38, the BECM does NOT like being disconnected or it may "forget" a few chores it must carry out

Anyway, keep on truckin and Happy New Year

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I get where you are coming from now.
Great work, & thank you again.
Happy new year to you also