Dash lights not working

Post Tue Jan 09, 2018 2:11 pm

Hi all,

Really hoping i can get help here.

The lights that are meant to provide general illumination to the dials are not working, so driving at night is pretty sketchy

I have a whole spare cluster that i borrowed new bulbs from and even tried the cluster itself in my car (although not long term practical as its for a 325 not my 316)

However still no illumination. All other bulbs work in the cluster, indicators, handbrake etc.....

Maybe is has something to do with the dimmer knob you turn the headlights on with?

Any help would be massively appreciated

Post Tue Jan 09, 2018 2:42 pm

Have you replaced or bypassed the dimmer?

Post Tue Jan 09, 2018 2:43 pm

Satan wrote:Have you replaced or bypassed the dimmer?

no i havent had a chance to look at that panel yet, is it relatively easy to get off?
And how would i go about bypassing it?

Thanks for replying so quick

Post Tue Jan 09, 2018 3:29 pm

Twist the knob off and unclip from the rear if I remember correctly and pull out backwards. Could just be dirty contacts.

Post Tue Jan 09, 2018 3:31 pm

Satan wrote:Twist the knob off and unclip from the rear if I remember correctly and pull out backwards. Could just be dirty contacts.

awesome, yeah i was wondering if it twisted off but just wanted to make sure i wasnt going to snap it.

I'll give it a go after i drive home this eve and report back thanks

Post Wed Jan 10, 2018 10:07 am

Satan wrote:Twist the knob off and unclip from the rear if I remember correctly and pull out backwards. Could just be dirty contacts.

I gave it a go but the knob definitely doesnt want to twist off.

Any ideas?

Post Wed Jan 10, 2018 12:18 pm

It unscrews from its metal shaft. If you pull the knob out as if you were switching the lights on you will see a hole in the shaft.
A thin screwdriver or something pushed through the hole will hold the shaft stationary whilst the knob is unscrewed.

Post Wed Jan 10, 2018 1:33 pm

Missed this one!
To bypass the dimmer, to check if it is the problem, pull out the rear ashtray, followed by the bulb and its holder that illuminate it. Pull off the brown/white wire, and connect this to a good body earth. Handbrake securing bolt is ideal.
If the panel lights now work, the dimmer is at fault.
Note that this fault renders your car technically unroadworthy, since lack of illumination of the speedometer is a MOT test failure point - speedometer not working is fine, but not being able to see it is not.
Your spare 325 instrument cluster is fully interchangeable with the 316 one, apart from the fuel gauge, if the cars have different tank sizes. The differences in the engines are accommodated by the coding plug pushed into the lower right front of the cluster.

Post Wed Jan 10, 2018 2:00 pm

Thanks for the advice, fiiinally managed to pry off the knob with the advice for the hole.
took the dimmer out, contacts looking very corroded. Tried giving it a gentle wire brush but to no avail.

I'll try the bypass method when i get a chance.

With the 325 dash, the strange thing is that my 316 dash actually has no coding plug in the lower right corner. So seems i cant use that cluster?

Also is there maybe a fuse i could be checking?

Post Wed Jan 10, 2018 2:11 pm

There was an early version of the E30 cluster that used a coding 'plug' inserted in the back of the cluster. The place where it fits is still marked on the back of later clusters. They still should be interchangeable.
The fuse for the dash panel lights is also the fuse for the parking and tail lights on the RH side of the car and the number plate lights, so if these are working it's not a fuse problem.

Post Wed Jan 10, 2018 2:25 pm

Awesome, feel silly that i missed the plug now but i'll have a look at that asap.

Roger that, fuse is good.

Thanks Again, i'll report back tomorrow

Post Wed Jan 10, 2018 8:25 pm

My Cabriolet's dash lights often fail to come on. A 'Millenium Falcon' style thump does the trick and they come on. All part of the charm!

Post Thu Jan 11, 2018 3:24 pm

Hi Brian,

I had a go at trying what you said today

I touched the spade connector on the brown earth wire on the bulb in the rear ash tray to the handbrake nut and bolt right next to it when the headlights were on and i got nothing.

Its worth also noting though that the bulb seems to also no be working.

I used a DMM on the brown wire to the not and bolt ans also got nothing.

what shall i try next? the lights in the dash were working very dimly when i picked up the car recently so at least i know its worked fairly recently

Post Thu Jan 11, 2018 11:58 pm

Have you tried turning the light switch fully clockwise?

Ben

Post Fri Jan 12, 2018 12:06 am

BenHar wrote:Have you tried turning the light switch fully clockwise?

Ben

Hi Ben, yes I have tried that unfortunately

Something worth noting is I realised my front Ash tray lights aren't working either so maybe there's something to be drawn from that?

Post Fri Jan 12, 2018 8:55 am

Does the rear one work?

Post Fri Jan 12, 2018 9:02 am

Satan wrote:Does the rear one work?

no it doesnt Satan.

However, brian mentioned that the side repeater etc also runs on the same fuse so i think that its not a blown fuse.

Up to now i've tried placing the earth wire from the rear ash tray light on the handbrake bolt to bypass the resistor in the headlight dimmer but that didnt work. I also placed a DMM on the earth wire and handbrake bolt but got no reading.

On to the next diagnostic step?

Please rescue me

Post Fri Jan 12, 2018 12:14 pm

Ah I was going to suggest if it worked to the lamp to the front ashtray, buy some spares they are capless lamps not sure which ones exactly but BM knows what they are.

My son had an issue not with the dash lights but sometimes if you pushed the rod in the headlights wouldn't turn off in the end a replacement unit was sourced, there must be a way to either short the connector from the switch so its bypassed and the dash shines at full brightness and to stick a meter on to the switch and twist the knob to check the readings.

Post Fri Jan 12, 2018 3:01 pm

Satan wrote:Ah I was going to suggest if it worked to the lamp to the front ashtray, buy some spares they are capless lamps not sure which ones exactly but BM knows what they are.

My son had an issue not with the dash lights but sometimes if you pushed the rod in the headlights wouldn't turn off in the end a replacement unit was sourced, there must be a way to either short the connector from the switch so its bypassed and the dash shines at full brightness and to stick a meter on to the switch and twist the knob to check the readings.

Ok slight progress,

I put a DMM on the circular resistor in the light switch and could see the voltage changing as i rotated the knob. This makes me think that my dimmer is actually good? can someone verify that (im a complete novice with electronics)

So my last thought with the state of things is that i have a dodgy wire somewhere maybe? so the dimmer works, but the lights behind the dash + the front and rear ash tray lights dont work.

So can anyone direct me in which wires i should be checking?

Post Fri Jan 12, 2018 6:01 pm

Where are you based?

Post Sat Jan 13, 2018 7:55 pm

e30Ambitions wrote: I put a DMM on the circular resistor in the light switch and could see the voltage changing as i rotated the knob.

You wouldn't measure any change of voltage as the dimmer was rotated unless at least one of the bulbs controlled by the dimmer was working. Is this so, and if so, which one(s) are working?
The dimmer is a variable resistance, not a variable voltage source, and the minute current drawn by a DMM would have a reminisce effect on the voltage across the dimmer.