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Good Evening All,
Sister-in-law's 240 has a bulb out indicator on in the instrument cluster but with no apparent "bulb" out. Seems to be triggered from the lights as during the day the bulb out indicator stays off even when applying the brakes.
I've replaced the round red relay to no avail. Anyone have any suggestions on troubleshooting this one.
Thanks for all your help in the past. The BB is a tremendous resource.
Marty wolfson
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Hello All,
Probably the last recommendation was the most apropo:
"so as a recommendation, check your work"
I checked grounds first per John, but that didn't solve the prob. Next, I swapped bulb and bulb holders from my other 93 sedan and that made all the difference.
Turns out that the bulb holder was the culprit. We had new and same make bulbs in the bulb holder but that didn't turn the bulb out indicator off, Fooling me was the fact that the taillights worked perfectly, but prob enough difference in resistance existed at the connection either with the bulb to bulb holder, or bulb holder to the circuit board which caused the activation of the bulb out sensor.
So.....if your bulb out sensor is on I suppose the protocol would be install new bulbs first. Then clean up the bulb holder, then check the sensor relay.
Thanks to Art, there's now archived some nifty troubleshooting pics.
Again, thanks to all that responded.
Marty
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Well, I am usually the one getting help, but maybe I can help with this. I have had the same exact sounding issues with two of my 240s. I tried new bulbs, new sensors, new fuses, etc. What cured it for me was simply cleaning the black ground wires by unscrewing them and wire brushing them and the spot where they screw back in and also cleaning the tiny connectors in the plug for each light assembly in the back. I used very fine sandpaper, black, and ran it into the connectors where the the usual male plug would go. This did the trick for me coincidentally on both cars. No guarantees, but I hope this helps. John
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Gee John,
I'm going out there right after my cup of coffee and give that a shot. Never thought about the ground wires.
Marty
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More specifically to one post below, I have read that different brands of bulbs will trigger the bulb-out circuit because they have a different resistance. Did this occur after changing a bulb? If so I go with the former explanation. If it started out of the blue and all bulbs are in fact working, I go with Art's and the fact that damp weather has come would support the possibility of corrosion affecting the current that is sensed. I have also experienced the soft lead contacts on the bottom of bulbs flatten over time and not make good contact with the socket.
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Marty, ya gotta get the info for which bulbs.
The tail lights would trigger it from the mid position of the light switch.
The head lights are indicated if the light switch is all the way on,
And of course, the brake lights when the pedal is used.
My experience with false warnings is mostly oxidation on sockets or connectors, not bulb brands or age differences.
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Art Benstein near Baltimore
You spend the first two years of their life teaching them to walk and talk. Then you spend the next sixteen telling them to sit down and shut up.
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Ok Art,
Yup more info would be helpful. That's the problem with us poor thinkers. Half of our problem solving if figuring out what the problem actually is.
The bulb out sensor dash light is actuated by the light switch in mid-position so I assume that my prob is with the taillights or the front running lights.
I swapped bulbs, I swapped bulb holders, and fiddled with the bulb holder as it made contact with the circuit board, all to no avail. The indicator light stayed on.
So, whaddaya think. Where do I go from here.
Marty
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OK, yes, the taillights. The most finicky of the three circuits. Some tips:
1 - the corner lights up front are not involved.
2 - to make testing easier, disconnect the small red (D61) wire from the alt and then ignition on will allow the sensor to function without the motor running.
3 - with sedan lights, eliminate the dual filament bulbs first, by removing both. Work in pairs. Be sure those bulbs are in the correct direction; yes you can jam them in backward.
4 - I know you swapped relays, but you could have two burned ones. Test the sensor by forcing the currents to balance. Bridge the two load side terminals like this -- the warning should not come on.
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Art Benstein near Baltimore
With her marriage she got a new name and a dress.
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Hi Art, Will and Oscar
Well, had a chance late this afternoon. Turns out that bridging socket pins 12 and 13 (Red and Brown/White) with the dash light initially on (car running with the running lights on) does nothing to turn the dash light out.
I'm assuming that even if I had a prob with the taillight bulbs, by bridging 12 and 13, I should still turn the light off. Correct?
I'm hoping that this still could be an easy one.
Marty
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Your results would tend to indict the bulb out sensor. But, there's still a reprieve, if one of the two fuses, #15 or #16 is passing less current than the other because of corrosion.
Another way to convict the bulb sensor is to be able to remove either fuse #15 or #16 and observe no correlating outage of that side's lamps. That would most likely happen when the sensor windings have melted together like these did.
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Art Benstein near Baltimore
When asked what time it is: "Do you mean now?"
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Evening Art,
Feel like a yoyo. Back and forth from the computer to the garage. Anyway,
With (white sedan - the problem) car running and taillights on, pulled fuse 15. Bulb out indicator lamp on dash remained on, but the taillights on the left side were not energized. Pulled fuse 16 and bulb out indicator lamp went off and so did the right side taillights. Re-installed fuse 16 and right side taillights were energized and the bulb out indicator lamp came back on. So........
Came back in the house and was heading for the computer when my wife asks if it's hard to access the bulb out relay. No "I said". Why don't you swap the bulb out sensor that you know is good from the the red sedan, she quizzes. Back out to the garage. Incidentally, it's getting cold in upstate NY. We're getting in the 30's and there were some snow flurries today.
So I swapped the sensors. Bulb out indicator lamp came back on, and in the red sedan the swapped sensor worked fine. Conclusion - it's not the sensor.
Maybe tomorrow, I'll fiddle around with the bulbs again. I might just take the bulbs and bulb holders out of red sedan to place in white sedan to see.
If you have any other suggestions, pls let me know.
Marty
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Hiya Marty,
OK, so you know it is not the sensor. Yet you balance the loads (with the paper clip) and the light remains on. The only conclusion I can draw from that is the sources are not balanced - i.e. either the circuit of fuse 15 or 16 is not pulling its weight.
If a cleaning of those fuses did not fix it for me, I would then force the sources to be balanced by bridging sensor pins 15 and 16 (aptly numbered if I might observe) where the white and gray wires enter. Have not needed to go that far, though, so as a recommendation, check your work.
1. No bulbs installed, should be no warning light.
2. Only the 4W bulbs installed (not the dual filament ones) should be balanced.
3. Grounds at tail lights should not affect this while you have 12 & 13 bridged, but a poor ground certainly could be the original gremlin, just not according to the results you're seeing.
You can work on this inside if you take that tip I gave you about the alt D61 terminal.
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Art Benstein near Baltimore
"I am going to buy a Volkswagen or a foreign car."
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Good Morning Art,
Can't get a better cookbook than what you provided. Have some (interfering) work today but will attempt another crack at it tonight or tomorrow and will report.
Thanks much,
Marty
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Art, I want to steal all your photos. You're like a rolodex of useful pictures. I never knew I could do that to test the bulb-out indicator. After replacing the shorter wiring to my left rear running lights, I've never been able to get rid of that light, and never wanted to spend the money on the relay.
Awesome-sauce.
--
1990 740 Turbo, on its way to stock specs, maybe beyond
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Some people report that changing a bulb out will sometimes result in the light coming on. In that case the advice is to change out its companion on the other side of the car. Seems the sensor is looking for an imbalance in the circuits and a new bulb might have less resistance than the remaining old one?
Other wise I would probably clean up all the bulbs and sockets and hope that action would equalize the resistance.
Randy
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Hi Randy,
Well, I did some bulb cleaning and swapped bulbs and bulb holders to no avail. Guess I could do it some more, but I don't think that's the prob.
Hmmmmmmm, where do I go from here.
Marty
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