Quick question: Some months ago I replaced a burnt out license plate bulb. Soon after that I noticed that the bulb failure light on the dash would come on for the first few minutes after starting the car. The indicator would flicker while the car idled and when I drove away. It would turn off as soon as I applied the brakes. I did a walk-around and checked all the bulbs. All lights were functioning properly. As time went on, the bulb failure light stayed on longer. I know that the failure light comes on when the left and right hand side circuits are not balanced. So there is an imbalance somewhere. I changed the other license plate bulb just in case but I don't think that those bulbs are part of the failure detection circuits. No change in symptoms. In fact, over the past week or so, the failure light stays on all the time. Today I took out EVERY bulb, inspected it, cleaned it, applied some contact grease and re-installed it. No change. I expected to find a partially corroded connection. Nope, every socket and bulb looked pristine.

Anyone have any ideas what to do next, short of replacing every bulb with a new one? I should have measured the resistance of every bulb while I had them out but it never occured to me at the time.

I suspect a flakey ground somewhere. Or perhaps the failure relay is faulty. Maybe one of the coils is gone in it or the reed switch has failed closed.

All the lights are working correctly.

Bill
--
Volvo Info Site 1990 745GLE 16valve

Ok, Thanks for all the good advice. I pulled out the relay panel and had a look at the relay. It was fine. No evidence of hot spots or failing connections, etc anywhere on the board in general. All looks healthy. But doing the operational tests that lucid suggested, I noticed that one of the low beams was burned out. It wasn't up until then. So that was the culprit. I put in a new bulb and Voila!, no more BF relay signal. It must have been on the verge of failing all this time and final let go, especially with me poking around at it.

Ah well, at least I know that all the connections, sockets, etc are in good shape on the car.

BTW, the relay panel was much easy to pull out if the cubby hole ABOVE the ashtray is also removed. On my car the wiring bundle was hung up at the back and needed to be lifted over an obstruction to free it up to allow the panel to move forward. Having the cubby hole removed allowed me to reach in and guide the panel and wires out without undue force. To remove the cubby hole, you have to carefully pry off the little cover on the cigarette lighter to get access to a philips screw holding that panel on. Lining up the screw to put it back on was a pain.

Glad I sorted all this out now rather than at -20C in January.

Thanks for all the great advice.

Bill
--
Volvo Info Site 1990 745GLE 16valve

Bill,
You got lots of good responses, but a couple don't apply to your car, in terms of which lights are tested.

• The License Plate bulbs haven't been part of the BF sensing since about 1977. So they aren't among the usual suspects for most of us.

• My '93 greenbook diagrams (and all earlier ones I've seen) show no testing of Parking Lights (front or rear). Must have added them after '93 if they are on Tom's diagram.

From '79 thru '93, the BF sensor checks 3 lighting groups:

1. Both Brake Lights + High Light (Operation and lights can be tested with key OFF or out)
2. Both Tail Lights (Need Key ON + Light Switch on 1st position to test BF operation)
3.Both Low Beams ( Key ON, Switch on 2nd position to test BF operation)

By trying these one at a time, it's easy to identify which of the 3 is bothering the BF sensor.
--
Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67

Thanks everyone! I'll pull the rely tonight and have a look-see. Will let you know the result. Gotta love this brickboard. Think I will send Jarrod a donation.

Bill
--
Volvo Info Site 1990 745GLE 16valve

You got some good answers.

That BFWS (bulb failure warning system) relay is used on 1986+ 200 series and 700 series and 940s. If you decide to try a used unit, that should give you a wide field to find one. Get more than one, negotiate a deal with the yard owner. Maybe he/she would like to have a "known tested good" unit on the shelf - the ones you return.

Good Luck,

Bob

:>)

I had a similiar problem. I could not get the bulb out indicator to go off. I replaced all of the bulbs with matching pairs. I cleaned the sockets. Nothing worked until I bought a new bulb out relay.
Bulb out relay $64.15 (free shipping over $50)
http://catalog.alloemvolvoparts.com/
It has never come back on.
Keith
--
1990 740GL Wagon 223k AW70L B230F 8 Valve Non-Turbo Regina

Bill,
You can check for corrosion on the relay pins and the stabs connections under the fuse/relay panel.

If you have the red Hella Gluhlampenkontrolle, Volvo part number, 1362370, and to verify that it is working correctly, pull it and make the following checks with an ohmmeter, test light, or buzzer. This is from a 1995 940 wiring diagram but is should be the same for the 740. I played around with a spare and at least one small alligator clip on a test lead would be most helpful.

Reed switch, pins K and 31 should be open.

The following should have continuity.
The wiring diagram shows "54S" and the relay had "54".
From pin 54 to coil pin 54L (Left brake light)
From pin 54 to coil pin S (3rd brake light)
From pin 54 to coil pin 54R (Right brake light)

From pin 57R to coil pin 58R (Left parking/tail light & Right parking light, rear)

From pin 57L to coil pin 58L (Right parking/tail light & Left parking light, rear)

From pin 56b to coil pin 56bL (Left low beam)
From pin 56b to coil pin 56bR (Right low beam)

Thats all 13 pins. Good luck.
--
Tom F Four 940s, RIP '78 244

It is possible that the failure warning relay is going bad. Especially if you get a warning when you first start the car and no lights have been turned on yet and you haven't put your foot on the brake. (If someone can think of a monitored bulb that comes on under that condition, please tell me.)

The problem is that it is an expensive relay to swap-out, and it would be a rather complex one to get into and resolder all the solder paths.

replace both of the license plate bulbs with identical ones perhaps.

the bulb out detection in our cars works by measuring difference in resistance between the left and right sides of the vehicle, thus sometimes two different bulbs of a different brand will cause it to happen.
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Yes, I replaced both license plate bulbs with Volvo bulbs.

Bill
--
Volvo Info Site 1990 745GLE 16valve

you cleaned the bulb sockets, but have you tried disconnecting the rear light wiring harnesses and cleaning the ground connections there? perhaps some dielectric grease (or vaseline) also.
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'