2000 Volvo S40 Headlights coming on randomly by themselves

BJBROWN17

MEMBER
2000 VOLVO S40
4 CYL
FWD
AUTOMATIC
12,000 MILES

Got an interesting problem. Came out to find my headlights on one morning after I had arrived at work. A co-worker advised me that my lights were on. The headlight switch was not pulled out - the headlights just came on by themselves. Since that first morning, it has been sporadically happening a few more times. (It's not consistently doing it though) Other times, after verifying the headlights are off when the car is turned off, I'll return to the car a couple hours later to find the headlights came on by themselves again. Finally, it killed my battery to the point it'll barely take a charge now. Please help.

4 Replies

VOLVO SERVICE ADV

MECHANIC
175 POSTS

SOUNDS LIKE THERE IS A SHORT IN THE SYSTEM, POSSIBLY THE RELAY. HOW ARE THE CONNECTORS TO THE HEADLIGHT BULBS? ARE THEY BURNT? ARE THEY LOOSE?

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Wednesday, October 6th, 2010 AT 2:35 PM

BJBROWN17

MEMBER
2 POSTS

No they are not loose or burnt

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Wednesday, October 6th, 2010 AT 2:42 PM

VOLVO SERVICE ADV

MECHANIC
175 POSTS

HOW IS THE CIRCUIT CARD ON THE ASSEMBLIES? ARE THE CONTACTS WORN OUT/CRACKED? SOLDER POINTS?

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Wednesday, October 6th, 2010 AT 2:52 PM

JIS001

MECHANIC
3,411 POSTS

Looking at the wiring diagram, it looks like the central electronic module has a built in relay for the headlights on them so the module will most likely be the cause of the fault but you should take it in for proper diagnosis. In the meantime, when you leave the car, pull fuse #19 (15A) in the engine compartment. That fuse controls the internal relay in the cenral electronic module for the headlights so that the headlights do not come on and drain the battery. Good luck and keep me posted. ;)

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Wednesday, October 6th, 2010 AT 9:37 PM