Dash light woes 20vcq

[jimmcf]

Greetings all,

i am hoping someone will be able to help me out with a problem that's driving me absolutley nuts.

Previous owner of the car at some time had a problem with the dash lights, at the moment the following does not light up

heater controls
aux gauges
fag lighter
ash trays front and rear
diff lock diagram (all bulbs resoldered by me)

Now on taking out the instrument cluster i can see that a feed has been taken direct off the light switch (green wire with red stripe) and an earth made on the steering column, now what this person has done to get the i.c lights only to work is to use the new feed and solder onto each bulb in turn a wire a bit like xmas tree lights. (see pic).

I am stumped now as to how to fix this, i have no power going to the dimmer switch in the dash and having tested the dimmer it still varies the resistance when you turn it, i have even taken it out and just popped a small wire over the 2 posts just to see what happens.

All the fuses are ok in the fuse box, the glovebox light works fine, the rear number plate lights work fine. The only part that i am suspicous of is the booster relay behind the aux gauges and have another coming soon to try out, however i need to sort out the ins cluster first.

Any thoughts guys and girls, btw i am not at all great with wiring diagrams and have tried to find the feed to dash for the lights but failed.

Sorry for the long first post, hope you can help

[newsh]

The dimmer for those lights is actually in the cluster, maybe that has failed? Its just visible in the top left of your picture, held in by 2 brass nuts one of which can be seen.

[jimmcf]

I have tested the dimmer and it does show variable resistance when rotating the knob, i have also by passed it altogether with it removed and a piece of wire between the 2 posts, didn't have any effect, i have continuity between the posts but no power.

[newsh]

so no power getting to the dimmer?

[newsh]

You need to find out which pin the lights voltage is supposed to arrive on at the cluster and check for it there, if its not there trace it back to where it comes from or try powering it straight from 12v, if its arriving at the cluster but not getting to the dimmer, I'd start looking for a broken track or dry joint in the cluster. The cluster comes apart quite easily but watch out for the knobs which go though it to the front as they tend to fall out Have some masking tape ready to hold things in place if you're unsure about how it goes.

[jimmcf]

Well the million dollar question is which wire or pin provides the power. I have had the dash apart several times now i getting pretty quick at it, i didn't see anything obvious like dry joints (the dash does light via the xmas tree method in the pic) i think i need to find the power wire first make sure there is 12v to it and go from there, any clues what colour combo i am looking for would be really helpful and then i can go from there.

It seems quite a common problem usually fixed with blown fuses or shorting out bulbs in the glovebox, but not this time i couldn't have been that lucky.

[mcandmar]

Booster relay is only for the aux gauges so i would ignore that for now, you problem sounds further up the chain. Glove box light only illuminates when the sidelights are one, i spent a while trying to fix one before i realised that

Goto http://www.s2central.net/S2_Schematics/MY93-ABY-C.htm for wiring diagrams, these look like the ones you need

http://www.s2central.net/S2_Schematics/D/D44-16.pdf

http://www.s2central.net/S2_Schematics/D/D44-17.pdf

T26 Pin 1 and 4 look like the illumination input for the cluster. Yellow connector, Gray/Green wires.

[jimmcf]

mcandmar spot on with the colours, i have just got back into the house after andother session and yes that is exactly what i have so thank you. I also have power to it when the lights are on, dimmer has no power though still but does read from 0 to 23 on the multi meter so it suggests to me that it works.

the fault must therefore lie with the cluster itself, any ideas on how to fix it or am i after another one????

Thank you

Jim

[newsh]

You need to get to the back of that connector and see if that 12v power pin is soldered into the board properly. IIRC the 2 studs with the brass nuts are the electrical connections to the circuit board so maybe there's a track broken nearby or the track is not connecting to the stud properly.

[jimmcf]

Cluster in bits for about the 4 th or 5th time this week then, looks like it's rev counter and temp gauge out as a minimum, oh well probably can't mess it up more than it already is. Having looked at the board already a few times the tracks aren't that obvious as the board is black in colour.

soldering irons at dawn it is

[jimmcf]

Dash problem now solved.

After pulling the cluster apart and looking at the circuit board it was obvious what had gone on and why it had been wired how it had been.

The track from the pin that powers the dash lights goes to the dimmer switch ( if you are looking at the back of the dash it's the left hand one), this had burnt through leaving the copper track with a hole in it and slightly raised. There is evidence of other parts of the same track in different places having got a bit hot at some point but they all still work ok.

It's impossible for me to solder copper that thin, so my first thought was to run a wire from the pin direct to the dimmer switch, thus bypassing the broken track. didn't fancy that option after thinking about it lack of space circuit needs to be flush etc etc.

So i ended up soldering a wire into the wire in the loom that goes to that pin and then connecting it with a ring terminal to the left hand post of the dimmer.

Ha lights now dim and the heater controls now light up. All i need now is a new relay for the aux gauge lights and i am confident it will all light up.

Big thanks to the forum

[newsh]

Really glad you sorted it, excellent result Someone must have shorted one of the bulb holders at some point, possibly with the wrong fuse in in the fuse box.

I've soldered thin copper wire on top of a broken track before now but you have to be careful as the heat can lift the copper off the board. Sounds like you found a tidy way to fix it, it would be worth checking all your fuses to make sure they're the correct value.

[jimmcf]

all of the heater control wiring had been bodged and a 25 amp fuse instead of the correct 5 amp, so someone had tried to bypass stuff and ended up frying bits instead. I tell you until you guys came up with the correct colour wire and pin no i was stumped, it's taken me on and off 2 days maybe a little longer to finally get it sorted.

I had no chance of going over the copper track as it had already lifted, i did in a vain hope try electro cure the stuff you fix heated rear windows with but it didn't work had no continuity.

What did surprise me is that it's a fiarly common problem but nowhere could i google and find what i was after.

[newsh]

Took me 4 yrs to get my interior lights working properly with the door locks but with the help of this forum I got there in the end.

Turned out the wire to the central locking pump was broken in the wiring loom, under the carpet below the bonnet pull on the RH side.