(bulb out) indicator light problem

Hello to fellow volvo owners and enthusiasts. I've viewed this group often....lots of great info. I own a 89' 740 and I'm having a problem with the bulb out indicator light located in the speedo display. With headlights on, it stays on, if I put the high beams on, it goes off. All bulbs are working(I've checked every bulb and connection multiple times). This all started with a recent low beam headlight being replaced. I can live with the idiot light staying on, but it only serves to remind me that I might BE an idiot, since I can't solve a seemingly simple problem. I tried a second headlight, in case the first was somehow faulty, same problem. Any input would be greatly appreciated.

TIA,

MW

Reply to
mw
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My 2 cents.... I think the reason might be that after replacing one bulb you have two bulbs with different wattages now. Either check on the bulbs that they have the same watt number or check by removing the second old bulb and put in two identical new ones.

Viktor

Reply to
viktor

Viktor=Victory! It's fixed! I took the second new headlight and put it on the other side....bingo! Man, you just made my day. Thanks for posting, I really appreciate it! I always thought these non-specialty headlghts were generic/universal to replace. So I've learned something new today. Thanks again, Viktor!

Reply to
mw

The bulb failure sensor is super sensitive, even bulbs aged differently will sometimes trigger it. Replace them in pairs and you should have no trouble.

Reply to
James Sweet

"James Sweet" schrieb im Newsbeitrag news:JL4jh.1836$Lc5.271@trndny04...

That also explains why the lamp went out on high beam. High beam is used much less time than low beam. So the current it draws is still very close to the current a new bulb. The low beam is on permanently, at least in many European countries, so it has aged a lot. Viktor

Reply to
viktor

Yes, I will do this from now on. Plus, at least theoretically, the new bulbs of same manufacture should have , more or less , the same lifespan. Though, I guess, some parts fail prematurely. But since bulbs are relatively inexpensive, this is a good idea. Thanks, James

I kind of understood that it was a current problem, because of the high beam causing the lamp to go out. The thing is, I was leaning towards faulty wiring or even maybe a relay or something. I really would not have ever thought of the uneven current from the bulbs themselves. Sorry to get a little silly with the victory thing, but this problem had me vexed, on and off, for a number of days. When I was able to just change the bulb....well, I know it's a simple thing, but I was pretty happy. Appreciate you guys sharing your knowledge. Thanks!

Reply to
mw

They normally do. What I do is replace the pair, then keep the remaining good one in the car as a spare. That way if one burns out, I can pop that in to get me by until I can make it to the store.

Reply to
James Sweet

The bulb failure sensor does not monitor the high beam lamps, it only looks at bulbs that are considered critical.

Really I'm not sure why they bothered monitoring the headlights, you can easily tell if one is out. The sensor is very handy for the tail lights though since you can't see those.

Reply to
James Sweet

James, I'll be keeping the extra headlight I replaced, good idea. You know, I noticed the high beam wires branch off from the low beam (four headlight system). Just curious, how does the sensor exclude the high beams in this case. Would there have to be a direct connection by the sensor to the high beams? Why do you think the sensor light would go out when the high beams were enabled? MW

Reply to
mw

Pick up a Haynes manual and look at the schematic, that will answer your questions. The high and low beams share a common ground and the wires are all bundled into one harness but there's two separate circuits and only the hot leads to the low beams run through the bulb failure sensor. When you switch on the high beams, the low beam filaments in the outer lamps shut off and the high beam filaments come on instead along with the inner aux high beam lamps.

Reply to
James Sweet

I've seen these manuals at the local auto parts store. Although you've pretty much answered my question, I think I'll pick one up. Appreciate it, James MW

Reply to
mw

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