Headlights Quad

My 1993 XJ40 V12 has developed a problem with the two outer headlight units , when just the side lights are switch on with ignition on the two outer headlight unit bulbs have a dim glow ,but all lights operate as they should when switched to dip and full beam not sure where to start looking.

thanks for help

Hello! I’d check the ground points in the engine bay. If it doesn’t fix the problem then check the relay modules for cracked solder joints.

I will check ground points and relays tomorrow and let you know how i get on

I’ll second the grounds idea.

Hi have checked ground points which are all good and the relay modules in engine bay seem ok are there any other relays in the system .seems like there is low power going to both outer headlights when only sidelights are switched on .
thanks for your help

You mean you turn the headlight switch just one click from the off position and you get dim headlights? In my case the headlights stay off. Only the side lights and the tail lights turn on. The 2nd click turns the headlights on.

That’s right 1st position on key and get dim headlights but all works fine on position 2 and full beam .

What i meant to say is that when side lights are switch on and with ignition on the two outer head lights have a dim glow but when headlights are switched on they work fine on full beam and dipped so thinking they must be shorting out somewhere when just sidelights are on any ideas where to start looking.

I’d check the switch and the pcb for cracked solder joints.

Your first post implied that this problem is one that developed over time and hasn’t always been an issue. Also, it appears both left and right side behave the same way. A possible candidate is the headlight switch, especially considering this switch gets used a lot.

Oh, and my 92 behaves like Joseph’s - headlights do not come on when headlight switch is in first position.

Hi will check these and let you know how I get on

I have purchased a secondhand switch and PCB from ebay which will arrive at weekend so I can swap over and see if that sorts the problem as the pcb looks ok so could be switch

I have fitted the new used switch and PCB but still have the same problem have swapped switch from car with different pcb and car pcb with different switch but still same problem.

Hmm… I’ve been looking at schematics and not sure I have any good ideas, but I want to be sure I fully understand the parameters around your issue. It seems your issue started showing itself at some specific time. Are you sure the issue suddenly began, or did you first notice the issue at that time? Also, has there been any aftermarket lightning installed such as fog lights, or other? Have any other aftermarket electronics been installed?

Maybe you just have daytime running lights on that car? :smiley:

Hi a bit too dim to be daylight running lights but if the M.O.T. guy has a problem with it I will tell him it’s an up grade😆 . I noticed the problem a few weeks ago when checking for blown bulbs , I have one bulb to replace on drivers side fog lamp which are factory fit. Car has no aftermarket electronics .

I’m curious. Would your MOT inspection fail because the headlamps are dimly lit with the parking lights on? Seems they would focus on lamps that are not lighting when they’re supposed to, and not worry about lamps that are over achievers. Again, just curious.

Hi I think it should be ok as all are working fine .