So I have an odd issue with my front drivers side marker light, which is the amber square reflector/light that is mounted in the side of the bumper.

When I first got the 1994 XJ12, the light worked fine. Then I heavily washed the engine compartment (I know, I know... ) after which I had a host of weird electrical issues.

The issue I initially had was that this side marker light would not turn off, even with the key off, and in addition the alarm siren would just barely "warble" once the car alarm was armed and the locks would cycle several times upon arming.

Over a week of occasional driving and thus heating the engine compartment, the bulb ceased remaining on with the ignition off, and the alarm returned to normal, but now the side marker light will not light at all.

So here's the current problem scenario:

If I put a blown bulb in the front drivers side marker light, the "bulb out" dash warning appropriately lights.
If I put a new bulb in, the "bulb out" warning light stays off, but the bulb will not light. I have tried this with another new bulb with the same results.

I suspect some relay or maybe connector needs dried and cleaned? Any ideas on what to check first?

Thanks,

 

Hi Al,

If I remember correctly, the fail logic in the Bulb Failure Module (BFM) looks for a certain voltage drop across a resistor to sense current through the side and sidemarker bulbs. If the bulb filament is open or shorted the bulb failure warning will be illuminated due to either no current flow or excessive current flow. My suspicion is that your circuit has high resistance, perhaps due to corrosion on the electrical connector to the sidemarker lamp, the BFM, or on the ground point in the front left inner fender where the sidemarker lamp is grounded (marked LSG27B on the schematic). If my theory is correct, the BFM sees current flowing through the new bulb, but due to high resistance the current is too low to illuminate the bulb filament.




Just a guess but easy enough to test by cleaning the ground point and electrical connectors.

Cheers,

Don

 

Hi, some of these modules have bad welding problems.
You must dismantle the module and repair questionable welds.
I've repair lot of these modules with light problem.

 

Thanks for the excellent advice!

I'll try to take a look this weekend.