Driving in the dark

[njpumphrey]

Having not driven at night in my w123 230TE, I was disappointed to find that my dash lights had stopped working. I have had variations of this problem before, and have also searched the archives for pointers, but so far have not been able to solve it. There are no blown fuses in the main fuse box; the bulbs still work; the lights on the vent controls and the cabin light are also powerless; all other lights (indicators, hazards, warning lights, clock, reg plate light) work fine. I suspect it might be something to do with the headlight control switch but have no idea how to test this. Also, one of the posts mentioned a rheostat - what is this and could it be this that is broken? Any advice will be warmly welcomed as it is not a very nice feeling driving in a black hole. Thanks

 

[andy_k]

I'd check the fuses again, they may not appear to be blown but it's possible they have corroded enough not to get a good contact - take them out and give them a clean.

The rheostat you mention should only dim the dashboard panel itself so it's unlikely that is at fault but just for reference it's the same controller as your trip meter - just turn it instead of pushing it.

HTH

Andy

 

[Francois]

Firstly, the rheostat is a piece of electronic equipment that has a variable resistance. This is used in a car to dim the interior lights, including the instrument panel lights. If this is broken, then it can cuase the problem you described. This sits directly behind the lights control knob.(the one you use to dim the intrument panel lights)

Secondly, there is a fuse a the back of the intrument panel. This could have blown. (not sure on 123 though)

 

[Francois]

Sorry Andy, Looks like we posted at more or less the same time....

 

[njpumphrey]

I looked very carefully for a fuse on the back of the instrument cluster. I think it is only present on the W124, as all the things on the back were bulbs. As for the fuses, I didn't trust my eyes when they all looked intact, so I checked continuity with a meter.

I have never tried turning the trip meter button on any of my w123s. I wasn't aware that the level of brightness (or darkness!) was adjustable. I thought the w123s all come in a standard level of gloom. It would be brilliant if the solution is that simple - I will try when I get home tonight...

 

[talbir]

The red fuse on teh back of the instrument cluster was only introduced late 1986 - it only controls illumination of centre console switches, not the actual dash lights themselves.

Sounds like the trip switch or faulty dimmer/rheostat on the back.


talbir

 

[mezza]

Ahhh

I have 230E B-reg

The binacles are illumminated but the centre console is not - I just thought it was like that - do I remove the binacles to get to this mystery fuse or is there a more civilised method of repair

thanks

Mezza

 

[mezza]

p.s. my clock has never worked - is this related to the fuse mentioned above?

thanks

 

[Francois]

The clock problem could be related, but I have also seen that the two capacitors on the clock could have had their chips... This isn't to difficult to replace if you have a bit of experience with a solder.

 

[talbir]

Yes, you will need to remove the binnacles/instrument cluster to reach the fuse, which is fixed to the back of the cluster. It's held in a red bulb holder.

The clock is not related to this fuse - clock only has a +12V wire coming to it and is grounded by a copper strip which grounds all the gauges. Maybe worth checking the integrity of the single wire +12V connection, otherwise it's time to renew the 2 capacitors in the clock mechanism. The capacitors are not available from MB - they can be obtained from Maplin's or any other electrical components supplier.

 

[njpumphrey]

Cheers guys - a happy ending!!! I twiddled the trip meter button and the lights lit up I love this forum!

The clock is definitely on a different circuit and I agree it is worth checking the integrity of the power cable and earth before getting the soldering iron out.

Thanks again.

 

[mezza]

Good intell - I will get to work and let you guys know how I get on

 

[mezza]

I have tried to apply the above info to my 1985 w123 230E but I have not solved the centre console darkness

I couldn't find a red fuse holder on the back of the binacle, but I did find that the bulb behind the middle heater knob had failed

Are these bulbs wired in series like xmas tree lights or am I barking up the wrong tree entirely?

p.s. my binacle lights up fine and the potentiometer works ok too

any more tips?

thanks

 

[mezza]

I should also say that the gearchange indicator on my auto is illuminated but that it the only part of the centre console that is

 

[NormanB]

Mezza

I am not familiar with the 123.

But in the 124, I have found that these bulbs do not last for ever so it is worth checking them all/replacing all.

I did mine - I suppose about 12 - 18 months ago and darn it if the one in the centre vent control dial has just gone and blown again - and I have them on dim (ish) and do minimal night driving.

NormanB

 

[Grrrmachine]

Ive been nosing around here for a week now and Im finding so much relevant info - it's not surprising, it seems, that Im having the same troubles as some people before me.

I have this same problem - binacles and dash are dead, and so is the clock. They worked when I bought the car, and as soon as I reset the trip counter, the lights died and I've since found out that a bulb has blown in the binacles. Havent yet sourced a replacement, but is it true that the cockpit lights are mounted in series?

 

[turnipsock]

I doubt the bulbs are in series, this would make the whole thing very unreliable and a nightmare to find he faulty bulb.

Does things like the temp gauge work? Do the warning lights come on when you first turn on the ignition?

There is feed to the instrument pod, this should be a grey/violet wire.

This feeds the 'lights on' buzzer as well, if that doesn't work the problem is further back...probably the light switch.

 

[Bolide]

Xmas is coming

Timing is just right, guys! This time next month we'll be fault-finding last year's Christmas lights and cursing them

A good wind of the rheostat cures most dash illumination ills, I find. It's termed "friction cleaning" in the trade


Nick Froome
www.w124.co.uk

 

[turnipsock]

It may be there is a 'bald' spot on the dimmer, waggling it back and forward may clean it. The same wire goes to the lights on buzzer, if the lights on buzzer works and the dash lights don't...then the chances are it's the dimmer switch.

 

[television]

The most common fault is the dimming pot, they are wire wound and go open circuit, when they start to go people turn the control both ways, this moves the wire to give a momentry contact and next time you do it again until nothing. very easy to check with a simple voltmeter.
The lamps on the center console do not normally dim.

Malcolm