Recently the dash lights at night have been giving me a problem. When the headlights are on and the lowbeams are active, I can see the blue highbeam indicator light on about 10% of its full brightness. When I switch on the highbeams, the blue indicator light is bright as it should be. Then switching back to low beams, the indicator is that dim blue light again. When it's in the dim condition, the white lights for the instrument cluster is a little dimmer than usual. I can turn the dimmer dial to off and the dim blue light will go out along with the rest of the lights in the cluster as they should.
What am I looking at as a problem?

Thanks in advance.
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'86 sedan with 445,000 miles on the original engine and automatic transmission

I know nothing about 200 series cars, but I had this same exact problem in my 940. I cured it when I reflowed all of the solder connections on the back of the instrument panel. I spent many hours troublingshooting grounds etc. Then my gas gauge died, so when I took the instrument panel out to fix these contacts, I reflowed everything. Boof, weird lighting issues went away.

Well, I check and wiggled everything and found all secure. One thing I forgot to mention (sorry) was that when the blue highbeam indicator was on dim, both turn signal lights in the cluster were also on dim sometimes and would go off if I used the turn signal switch to make a turn, then they'd go back to normal after the turn was made. I'll pull the cluster and check the connections this weekend and post back.
Thanks everyone for your suggestions and thoughts.
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'86 sedan with 445,000 miles on the original engine and automatic transmission

Bob, the turn signal clue reinforces the cluster ground diagnosis. The turn signal indicators in the cluster are on the same ground. The clock and gauge stabilizer share that ground too, but I doubt the small amount of resistance is affecting them visibly. The reference below is from a '91 manual, not '86.


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Art Benstein near Baltimore

Testifying before a grand jury about a New York Yankees' brawl in a nightclub: "Nobody did nothin' to nobody."

Thanks again Art for your time and detailed info pics. This will give me a better starting point when I start my hunt this weekend. I'll keep all posted.
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'86 sedan with 445,000 miles on the original engine and automatic transmission

Bob, what you are looking at is a poor ground at one of the headlights. The grounds are at the end of the strip where the hi-lo relay hangs, for the left side, and at the washer bottle bracket on the right side. It could also be a corroded headlight socket. Try wiggling both first.

With some resistance in the ground, some of the voltage being delivered to the low beams is seen on the high beam filament, which is in parallel with the blue light on the dash.
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Art Benstein near Baltimore

"Always go to other people's funerals; otherwise, they won't go to yours."

With some resistance in the ground, some of the voltage being delivered to the low beams is seen on the high beam filament, which is in parallel with the blue light on the dash.

Once again you have managed to make me feel guilty about not really applying myself in my Electricity/Electronis courses, but we are sure glad that you did!

Randy

Art,


How would the rheostat affect brightness of the indicator, if your hypothesis is indeed correct?

Could a light leak in the instrument cluster become apparent suddenly?


Goatman

Very good question, Kyle. The ground shared by the indicator and the illuminators is a black wire through pin 4 of the half-round connector. One manual, not for an 86 though, says it eventually ties to the body at a screw just northwest of the shifter boot (or gear lever console as Volvo calls it).

If Bob would reach up and wiggle the half-round connector on the cluster, he might affect the symptom. Failing that, the black wire could be traced to where it gets screwed to the body.

Good catch!
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Art Benstein near Baltimore

The trooper stopped writing the ticket and said, "Well yeah, if that's what they're called. But I never heard of no circle flies...

Art,


If the problem is not mechanical (dislodged light shade), then the issue might be as you say with one small difference:

The headlight ground is not the problem, but the ground for the instrument lighting is faulty. The current then takes the path through the instrument lighting, back through the indicator, and through the high beam filament to ground. But in reality, could the blue indicator filament light and still carry enough current to light the instrument lamps also?


Goatman

Assuming the ground is entirely missing - open circuit, no, the 100mA blue light would outshine the two 2-watt panel lamps. But, according to a list of ground connections in the closest manual I have, the cluster wire shares a single-point ground with about a dozen other functions.

The headlight ground having high resistance would explain the blue light on low-beam, but the instrument panel ground being other than solid, is the only way the dimmer could shut off the errant blue light. It only takes 1 volt to get those warning lights to glow.

The easy first step would be to wiggle the cluster plug. Next would be to locate the ground point at the transmission tunnel.

As for the shade being broken, I don't know. It is a nice theory. I've had enough of these clusters apart to guess it isn't likely without some kind of really unusual damage, and I know Bob has had this car for a lot of miles.

Fun armchair diagnostics though. Aren't you itching to tear it apart and see what the real answer is?
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Art Benstein near Baltimore

"Well, sir," the cowboy replied, "circle flies hang around ranches. They're called circle flies because they're almost always found circling around the back end of a horse..."

My headlights are brand new units, but I'll give them a wiggle. I'll check the grounding points this evening and see what happens tomorrow morning when I head off for the daily grind.

Thanks for looking.
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'86 sedan with 445,000 miles on the original engine and automatic transmission