Main light switch 1993 940 Turbo Wagon 190,000+ miles

Tom1993940turbowagon · Post by **Tom1993940turbowagon** » 07 Feb 2008, 05:19

I've looked in the forum but don't find this problem. Hope I'm not repeating something.

When my wife turned the car off at work yesterday morning, the front lights did not go off and the battery ran down. After a jump and drive home, she realized that the front lights would not go off. I had to pull the fuses to turn them off.

The front lights stay on when the light switch (the switch on the left side of the dashboard with three positions, off, parking lights, and all lights) is in the middle position for parking lights.

The front lights go off when I turn the switch fully to the right into the position in which they should go on.

The rear lights seem to work OK - the rear running lights.

The brake lights all work fine.

The fog lights work.

The turn indicators all work.

I'm thinking it could be a problem with the relays. I checked all the fuses and they are fine. Wiring seems OK too. To my knowledge, we haven't run over anything that would get up into the undercarriage or engine compartment to foul up wiring.

Today is our 27th wedding anniversary and we were planning to go out tonight but if I don't get this fixed, I'll spend the night after work trying to fix this problem. If it's just a relay, I'll be able to take my wife out, so there's more at stake than just fixing the car. Help!

Many thanks.

Post by **billofdurham** » 07 Feb 2008, 07:06

Congratulations on your 27th anniversary and welcome to Matthew's Volvo Site.

By 'front lights' do you mean headlights or parking lights?

There is a headlight relay in the main fuse box. It is in the front row, second from the left. If it is not working I can see how the headlights would not work with the switch in the all lights position, but I can't work out why they would stay on when the power was switched off.

Bill.

Tom1993940turbowagon · Post by **Tom1993940turbowagon** » 07 Feb 2008, 07:09

Thanks. I should have been specific. I was referring to the headlights.

I figured that could be the problem. I ordered a new relay so we'll see. I'll let you know if that fixes it.

Whizzit · Post by **Whizzit** » 08 Feb 2008, 11:20

I am having a similar problem and will share with you what I do know thus far, it may or may not apply since the vehicles are different model years. I have (my wife has) a 1991 Volvo 740 Turbo with 190K miles on it. Currently, when her headlight switch is in the full on (far right) position, no lights come on, no dash, no parking, no rear, nothing. In the middle position for parking lights, everything works normally, inlcuding front, rear, and dash lights. The bulb failure relay was suspect (the large red relay in the left rear of the central electric unit (CEU)) since it controls the low beam lights in the full on switch position. I found this to not be the case, as the input terminal (56b, should read about 12-13 Volts) to the bulb failure relay did not have any voltage, so my problem lies prior to that relay. I have purchased a tone generator and amplifier and am going wire hunting. If or when I find something, I'll let you know on here.

Post by **billofdurham** » 08 Feb 2008, 11:45

Whizzit,

Welcome to Matthew's Volvo Site and thank you for the input. This sharing of knowledge (troubles) is how the forum has been able to help so many Volvo owners.

Bill.

Whizzit · Post by **Whizzit** » 08 Feb 2008, 12:19

Thanks for the welcome Bill. Although now that I have solved my problem, my sharing of knowledge probably will not help the original poster.

I installed an aftermarket radio in my wife's Volvo two Fridays ago. There were wiring harnesses available, but were really not saving me much work vs direct wiring. So I saved the $50 for the harness, found posts in Volvo forums about schematics and wiring diagrams, and hooked up the radio without a hitch. So I thought. The headlight problem wasn't discovered until later, therefore I never tied the two events together.

There were 4 wires left over that were not indicated on any of the information I had, and not being one to go hooking things together until I get some result (i.e. motors running, lights on, smoke, fire,etc.) I insulated and secured them in the dash. These four wires were Yellow w/ White (Qty 2), Pale Blue, and White. The two Yellow w/ White wires were terminated together in the rear of the old radio harness. When I cut them and installed the radio, I apparently cut a source to the bulb failure relay. I can't take credit for this myself, I stumbled onto this post after doing a search on this site....

https://www.matthewsvolvosite.com/chat/p ... php?t=6132

A few seconds stripping wire, a butt splice, and some heatshrink tubing later, I'm back in business. All lights working as before.

I am interested in seeing how this relay replacement works out. I removed my bulb failure relay, took the cover off, and was quite surprised to find a large amount of nothing inside. No moving contacts what-so-ever! Some induction coils and a few transistors, but nothing that should give the symptoms of the original post. I'd almost suspect the switch itself, as if a contact broke loose inside and is making contact where it shouldn't.

Many Cheers to everyone on this site for sharing their knowledge, and I must say that you have a wonderful online community. Thank you!

-Whizzit

ifar · Post by **ifar** » 27 Feb 2012, 02:57

Whizzit,

THANK YOU so much for posting your findings on this site. I just bought a 1994 940 Wagon and had the same issues with the low beams not working after an "attempted" stereo install. With further research on this site I'm sure I'll be successful. I will reconnect those two wires right away!

-ifar