The dash bulb-out indicator had been out on our '92 244 since we bought it a year ago. All the lights were working, so I spend my time on more immediate concerns. The indicator came on in position 1 (parking lights). The only clue to the problem was that one front parking light was slightly brighter than the other. I assumed that an incorrect bulb or an out-of-spec bulb was causing an impedance mismatch that triggered the bulb-out relay.

This weekend I took off the turn signal lenses and inspected the parking light bulbs. They were the correct type, and identical down to the manufacturer. However, the driver's side bulb was undoubtedly brighter than the passenger side bulb. Hummmm...

Looking closely, I saw that these were two-filament bulbs, and that one of the two filaments was larger than the other. I also noticed that the "big" filament was lit on one light, and the small filament was lit on the other, accounting for the difference in brightness, the impedance mismatch, and ultimately, the bulb-out warning indicator. The question was, why was current going to different filaments?

I removed a bulb from the passenger side parking light socket, and noticed that the bulbs' base have offset locating pins so they can into "screw" (10-15 deg rotation) into the socket in only one direction. The bulb bottom had two terminals, one for each filament, but the socket had only one terminal, which was mounted to a spring-loaded plastic disk. It seemed that the socket terminal disk was rotated 180 deg from where it should be. This disk has small tabs that fit into grooves in the socket to prevent it from rotating. There was no sign of mechanical damage, corrosion, etc.

I decided to rotate that white terminal disk one way or the other. I pushed the green wire going into the socket into the socket, which in turned forced the terminal disk forward until its locating tabs cleared the grooves. I then rotated it 180 deg and pushed it back down into the socket. I reinstalled the bulb and turned on the lights. The parking lights on both sides had the same intensity, and the bulb-out indicator was off.

In the grand scheme of all things Volvo, this was a minor problem. A PO or some mechanic probably accidentally rotated the terminal disk when changing a bulb. However, it was an interesting little exercise in troubleshooting.
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'88 244GL, '89 244GL, '90 244DL, '91 244, '92 244

Strange because the BFS circuit doesn't test the front parking lights—only the tail lights, stop lights, and Low Beams.

I have wired that unused (bright) filament in the front lights to act as a Daylime Running Light on several cars. To me it's less annoying than headlights all the time—plus the car is more noticeable from the side, where the headlight DRLs don't offer much.

Volvo changed a lot of things over the years, but my 83 factory wiring diagram book supports Bruce's comments...the front parking lamps are not part of the BFS circuit. Some BFS modules are extremely sensitive and making a supposedly unrelated change could correct (or cause) a BFS problem.

..somewhat unrelated, but Bruce opened the topic... I have rewired both kids' 240's for daytime running lights so that the inner high beam bulbs illuminate at one-third-power whenever fuse #1 is 'hot' (Key in position I or II, but not III), headlights are turned off, and parking brake is off. Reduced power is achieved by wiring a 1.33-Ohm, 60W resistor pack in series with the DRL relay's feed to the bulbs.

Advantages:
-the low beam filaments - obviously the most important headlight elements - are not used as DRLs, so will last longer;
-the high beam DRLs , even at low power, are visible WAY down the road, warning oncoming traffic not to attempt a pass on two-lane roads, or cross traffic not to pull out from a stop sign;
-at 35% power the filaments should last approximately forever.

A side benefit is that my double relay setup bypasses the resistor to provide full battery voltage to the inner high beams (ie: brighter) when they are switched on at night, and their current draw is removed from the already overtaxed headlamp switch. (Perhaps this is not a factor on later, plastic-lensed 240's with just two high beam filaments and a relay on the light switch.)
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)

Actually, the bulb failure does test for the parking lights, as both the front and the rear are on the same circuit.

-- Kane
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Blossom II - '91 745Ti/M46 ... Bubbles - '74 144GL/BW35 ... Buttercup - '86 245GL/AW70 ... The Wayback Machine - '64 P220/M40

I agree the front and rear lights are fed from the same fuses, but all 4 lights have separate wires, and the 2 rear lights are the only ones wired through the BFS to test for current balance. (BFS terminals 56R and 56L input, 58R and 58L output to bulbs)

I can't see any connection between the front parking lights and the BFS current sampling circuit.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Thank you, Kane, I was about to dig out my circuit diagram to make sure I wasn't hallucinating!
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'88 244GL, '89 244GL, '90 244DL, '91 244, '92 244

I reinstalled the bulb and turned on the lights. The parking lights on both sides had the same intensity, and the bulb-out indicator was off.

Did you start the car before checking the light intensity? Because the Bulb-Out test does not occur with the engine off.

I don't mean to be picky but there is no (logical) way a repair to the front lights would affect the BFS operation, as far as I know. Maybe we should call Art Benstein in?

Frankly, I'm baffled.


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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Well, I believe I owe the Board a retraction. My circuit diagram doesn't show the front parking lights on the BOR circuit. I should have checked my diagram before making such a claim. I went out this evening and pulled the plug for the light and the bulb-out warning light did not come on. I am at a loss as to why flipping the bulb filament coincided with the light going off. I removed the headlight bulb from the lens housing when I pulled it. Perhaps I jiggled something enough to affect the impedance a bit...

To paraphrase Dan Rather, 'I made a mistake in judgment, and for that I am sorry. It was an error that was made, however, in good faith and in the spirit of trying to carry on a BrickBoard tradition of investigative problem solving.'

At least we can say that rotating the terminal disk solved the problem of intensity difference in my front parking lights. The thread also brought out the very interesting method of using the second bulb circuit for running lights.

Please don't call Art in on me. Please...
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'88 244GL, '89 244GL, '90 244DL, '91 244, '92 244

Glen, you know I read anything you write. Might just be too late to be of any help, but this time, between you and Bruce, I find myself laughing at your mention of my name. Then, the Dan Rather analogy has me in stitches.

Here's my guess on the workings. The sensor works by surrounding a magnetic reed switch with two coils of wire wound separately but connected to the left and right lamps with opposite polarity so equal currents will cancel the magnetic field around the reed.

When the currents become slightly different, enough field is made to pull the iron insides of the reed switch into contact, but inside, it is arranged to latch (magnetically), or hold the contacts together with a smaller field than needed to make the contact initially. This prevents contact bounce.

If the unbalance is on the "hairy edge" of what is necessary to light the warning light, the effect of that hysteresis or latching is to have the warning either fully on or off, not dim, or flickering, so you might start the car twenty times with the same lamp problem, but only get the warning lamp ten of those times. Same effect your home heating thermostat uses.

Also, changing the current being drawn in the front parking lamps by a large amount, as would happen running the 25W filament instead of the 5W, because of the real resistances in the fuse and contacts, would affect the voltage available to the taillamps through the current sensor. Less voltage to one circuit would would make the same taillight load imbalance tip the scales - reducing or increasing the field around the reed switch, depending on whether it aids or bucks the load difference.

The one remaining factor in the bulb out warning is only important in dry climates at low altitude. The Volvo designed finooken valve piston seals shrink with low internal pressure causing false activation of the muffler bearing service indicator circuit, sometimes disabled by the do-it-yourselfer to prevent excess nylon gear stress on higher mileage cars.

Hope this helps as you feared, Glen.

What Art said... :-P

And now that I think of it, Art, I believe your last hypothesis is correct. I HAVE heard an exhaust system rattle recently and I replaced my finooken valve 500 miles ago with a ScanTech aftermarket unit. Yep, that's gotta be it!

Actually, Art, as we on the Board all know and appreciate, you are an extraordinary technical writer. Very few people have mastered the art of painting mental pictures that lead somebody through a physical process without resorting to language that is stilted, repetitive, or just plain boring. Fewer still have the generosity to share that talent with strangers. Your write-up on the blower motor repair is a classic of the genre. Collectively, you have saved folks on the BrickBoard HUNDREDS of hours. I know your blower motor instructions saved me at least 3 hours when I replaced a heater core two weeks ago.

Now if we can only get Jarrod to consider giving you a cut of the tips!
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'88 244GL, '89 244GL, '90 244DL, '91 244, '92 244