W210 interior light gremlins

[welland99]

The passenger side vanity mirror light doesn't work. I know that to many, this might not be a very important light, but in the darkness, i find it is probably the besst light that a passenger can use to read a map because all the central lights are too bright for the driver.

I cannot understand why the front central map light shines to the right. i think it should shine to the left. It must be designed for the left hand drive market

Now back to the vanity mirror light. I've got two new bulbs (one for driver's side and one for passenger's side). Both bulbs work in the drivers side, but neither work in the passenger side. In fact, I have also swapped the bulb holders over and both of these work in the drivers side and neither work in the passenger's side.

I've checked the contacts with a voltmeter. The passengers contacts show 12 volts every time the switch is on, but a bulb doesn't illuminate. How can this be?

I reckon the switch must be ok as it switches on and off every time. But how can 12v be present across the contacts, but a bulb won't illuminate.

Any ideas of where I can start?

 

[BlackC55]

maybe you have 12V but not enough current.

Have you checked the continuity of the bulbs?

 

[BlackC55]

Or swap the bulbs to the other side?

 

[welland99]

maybe you have 12V but not enough current.

Have you checked the continuity of the bulbs?

Yes tried that. tests fine.

 

[welland99]

Or swap the bulbs to the other side?

Tried that as well. Both bulbs work fine in the driver's side. I also tried swapping over the bulb holders too. Both work fine on the driver's side. I checked the voltage between the contacts in the bulb holder, not at the plug. So I know the problem isn't at the plug.

 

[welland99]

maybe you have 12V but not enough current.

I agree this seems to be the case, but how can this be?

 

[BlackC55]

burnt contacts further down the wire?

You will have to trace it back. You need a diagram really

 

[welland99]

You will have to trace it back. You need a diagram really

ANybody know if there is one on the web somewhere?

Does anybody know if it's possible to dismantle the sun visor to check the wiring inside? I've checked all around and can't see any obvious clips.

 

[Ted]

I agree this seems to be the case, but how can this be?

It is possible to measure a voltage with a high impedence voltmeter, even though there is insuficient current to power a bulb - I have picked up 18v between wet sawdust and common on a truck in the past. Put the bulbs back in and you will find that the 12v disappears.

My advice is never to trace an electrical fault like this with a voltmeter. Always use a test light.

 

[lynall]

Teds spot on about the test light ive seen several people do this using a meter and running around in circles with no results, ive got a bulb with 2 wires soldered to it works a treat.
Use a flat screwdriver to remove the whole vanity mirror assy from the visor then you can see the microswitch.



Lynall

 

[welland99]

I noticed that when the visor is unclipped from the front position to move to shade the side window, the working drivers light is switched off. This got me thinking about the two visible contacts that become visible in the clip on the ceiling.

I think that if these two are shorted together this must complete the circuit with the lamp. At this point the cabling and microswitch inside the visor must be out of the circuit.

Will try fiddling with this tomorrow to see if it helps.

 

[welland99]

Anybody got a LHD W210?

I cannot understand why the front central map light shines to the right. i think it should shine to the left. It must be designed for the left hand drive market

I just wondered if anybody here has a LHD W210? If yes, to which side of the car does the small map light in the ceiling between driver and passenger point?

Mine is RHD and it points to the right. I think for RHD it should point to the left.