w202 glovebox light

[cabvw]

Hi guys

Been having a few problems on my w202 c200 glove box light, i've replaced the bulb but no joy, checked the fuse under the bonnet and its not blown....i've also checked the switch and it seems fine..?

Anything else i might have missed..?

Thanks for your help in advance.

Cabvw

 

[219]

Do you have a multimeter ? You can buy one quite cheaply in B&Q or wherever .

The first thing to check is by metering for voltage , this means grounding the earth wire of your meter to a bare metal part on the bodyshell (if you lift the carpet in the footwell see if there is a metal screw going into metal somewhere - this should do) , you will then be using the positive probe to look for voltages . Set the meter to d.c. volts with a range greater than 15V.

I'm not sure whether this circuit switches on supply or ground side of the lamp . The way to check is , with your meter set to volts and the glovebox switch button pushed in (off) check the voltage on either side of the lamp and either side of the switch .

If you read a constant 12-14 V (or thereabouts) on both sides of the lamp and one side of the switch , then the switch is breaking the ground return (earth switching) . If only one side of the switch shows a positive voltage and everything else shows 0V , then it is positive switching .

If you cannot get a positive voltage anywhere on either side of the lamp or either side of the switch , then the fault lies elsewhere and you would need to trace the wiring back to the fusebox .

I would expect it to be earth switching , in auto electrics , ground wires are usually brown so this will help to confirm .

Assuming you have confirmed the presence of a positive supply to one side of the circuit , we now need to check the earth continuity on the other side of the circuit . (Just to be safe , first remove the fuse that protects this circuit in case you accidentally short the positive side to ground during this check .) Now set your meter to continuity or resistance , if it has a 'beep' setting , use this . With the meter still grounded to your earth point on the floor or wherever , now test the opposite side of the lamp/switch where you did NOT find a positive voltage earlier - either your beeper should 'beep' or your resistance meter should indicate zero ohms ; if it does not then you have an earth continuity problem and will need to trace the ground side of the lamp/switch assembly back to the bodyshell .

While you have your meter on resistance/continuity , check across the lamp : there should be some continuity / lowish resistance measurable ; although it is a new lamp , it just could be faulty . Also meter across the switch for continuity pressing/releasing the switch button , looking for a change in readings ; if it does not change - stays open circuit then the switch is faulty .

Hopefully this will allow you to isolate the fault .

 

[bibamus]

I know you must have checked, but, it only comes on with the ignition on.

Allan

 

[cabvw]

Many thanks for the reply, i have checked with the ignition on, i'll get a tester and try it this weekend.

 

[grasmere]

what about a light sensor stopping it coming on in daylight - is that possible?

 

[mioba]

can you not take the interior of the glovebox out, maybe the connection has just come apart.

 

[shandy]

The glove box light gets its power from the acc. position on the ignition switch through fuse 14 in the main fuse box, it shares this supply with the cigar lighter so your first step is to check if the cigar lighter is working ,if it is check the wiring to the glove box light as previously described.