puzzling front sidelight 300TDI

robbiemcvee · Dec 30, 2018

was about to put my 90 300tdi through the MOT last week, noticed that the front nearside sidelight was out - went to replace the bulb and still nothing, checked fuse 15 - seemed ok but replaced anyway.

checked continuity from the lamp holder to earth - yep that's fine - checked the voltage and its reading 2.8 volts back to a good earth.

when turning on the lights, first click is sidelights - drivers side is ok (dim headlights) rear lights are on, second click is headlights - thats all ok including main beam.

I still cant work out why the nearside has just 2.8 volts - has anyone got an idea - really need my landy through the MOT now..

thanks all

Al2O3 · Dec 30, 2018

A multimeter is very sensitive when checking continuity. That doesn't necessarily mean that it will have a low enough resistance for the 12v supply to use. This seems like a dodgy earth to me.

robbiemcvee · Dec 30, 2018

Al2O3 said:
A multimeter is very sensitive when checking continuity. That doesn't necessarily mean that it will have a low enough resistance for the 12v supply to use. This seems like a dodgy earth to me.

i'll run another earth and see how it goes - thanks mate

bluehaze · Dec 30, 2018

Have you tried a spare connector?

I had a crack in one a few years ago that took me ages to find.

jamesmartin · Dec 30, 2018

youll probably find a new lamp and connector will help

robbiemcvee · Dec 30, 2018

no - that didnt work - noticed now that there is no voltage to the light and around 7ohms resistance to the earth on the engine..?

robbiemcvee · Dec 30, 2018

i changed both lamp and connector for a new set i had - still no luck

Al2O3 · Dec 30, 2018

robbiemcvee said:
no - that didnt work - noticed now that there is no voltage to the light and around 7ohms resistance to the earth on the engine..?

So the 2.8v has dropped to zero?
How are you measuring the resistance, via the earth, to the engine?

robbiemcvee · Dec 30, 2018

yes - the voltage seems to have gone - not sure why...im measuring the resistance form the light connector earth (black) to the engine

Al2O3 · Dec 30, 2018

robbiemcvee said:
yes - the voltage seems to have gone - not sure why...im measuring the resistance form the light connector earth (black) to the engine

So, with your multimeter you can get an obvious and good connection to the red/black supply wire and a good earth and get 0v when the switch is on? Is the tail light still coming on as they share the same supply from the fuse?

robbiemcvee · Dec 30, 2018

Hello, yes the rear lights both work

Al2O3 · Dec 30, 2018

robbiemcvee said:
Hello, yes the rear lights both work

Then the only two options, to my mind, are a break in the red/black supply wire (unlikely) or a bad earth from the front lamp connector. If the earth isn't good the electricity will simply go via the rear bulb to earth as they are in the same circuit.
Try taking the rear bulb out (on the same side) and see what happens.

robbiemcvee · Dec 30, 2018

Thanks again, ill have a go tomorrow, run out of steam now

Al2O3 · Dec 30, 2018

robbiemcvee said:
Thanks again, ill have a go tomorrow, run out of steam now

Aye, it's beer O'clock

robbiemcvee · Dec 31, 2018

Looks like a break in the cable to the positive, is these a connector hidden somewhere that takes red from the fuse to the red/black on the connector

Al2O3 · Dec 31, 2018

robbiemcvee said:
Looks like a break in the cable to the positive, is these a connector hidden somewhere that takes red from the fuse to the red/black on the connector

No, don't think so. Are you testing that live via a different earth, not the original earth?

robbiemcvee · Jan 1, 2019

All fixed, cut the wire next to the bulkhead and spliced a new one in.. mot next week..!

puzzling front sidelight 300TDI

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

bluehaze

Well-Known Member

jamesmartin

Well-Known Member

robbiemcvee

Active Member

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

Al2O3

Well-Known Member

robbiemcvee

Active Member

Similar threads