Low Beams don't work...

[Nathan]

So i'm getting very anoyed with not having my low beams working. The low beam check light hasn't come on at all since they stopped working. I can get the bulbs to light up and I've replaced the relays. I performed the test indicated in the Bentley manual and both the High beam and Low beam relay sockets failed the terminal 30 test for power. (Ignition OFF, test to ground, should have battery voltage, both had none) I also have a short that is on a circut without a fuse. There is a constant drain on the battery but no blown fuses and all accesories off. If I remove fuse 17 the drain reduces by .2 volts but since that fuse handles a ton of stuff that is hard to pin down.

Anyone have any experience chasing down similar electrical problems? Anyone have any idea what I should do next? The manual doesn't really help much after i've done the test as to what is means and other such help...

Thanks

[Geez Tech]

Good=12 volts?

Have you checked for voltage or does everything just "look" good??

[Nathan]

By good I mean that i've either switched parts out or i've tested them. None of the items that i've labeled as "good" actually produce voltage (ie the actual light and fuses/relays and the switch) so i'm not sure what you mean by "Good=12 volts?". I've switched the switch out with no effect and all fuses are visibly good (German fuses that you can actually see whether or not they are bad). Relays have all been replaced. The only things wrong I've listed already.

[arsevader]

By good I mean that i've either switched parts out or i've tested them. None of the items that i've labeled as "good" actually produce voltage (ie the actual light and fuses/relays and the switch) so i'm not sure what you mean by "Good=12 volts?". I've switched the switch out with no effect and all fuses are visibly good (German fuses that you can actually see whether or not they are bad). Relays have all been replaced. The only things wrong I've listed already.

Meaning you need to trace with a voltage meter where you are getting 12 volts. Work your way through the wiring until you don't have 12 volts, then you'll be able to find out what's wrong.

James

[Geez Tech]

Exactly James, verify you even have voltage, you can throw all the test parts you want at something but if the voltage isn't there then your going nowhere.

[Mot]

I had a very similar problem, my lows wouldnt work but the high beams worked fine. I never fixed it since im parting that car right now, but I would love to know how u end up fixing it nathan. Maybe we can fix it next weekend if its still a problem?

[arsevader]

Exactly James, verify you even have voltage, you can throw all the test parts you want at something but if the voltage isn't there then your going nowhere.

That's what separates good mechanics from poor ones. The poor ones just keep replacing parts till something is fixed (or even not fixed) a good one will test things untill the culprit is found. Pretty much everything on these cars can be tested, especially the electrical things.

You just have to be systematic and logical.

James

[AdamF 88iS]

Exactly James, verify you even have voltage, you can throw all the test parts you want at something but if the voltage isn't there then your going nowhere.

That's what separates good mechanics from poor ones. The poor ones just keep replacing parts till something is fixed (or even not fixed) a good one will test things untill the culprit is found. Pretty much everything on these cars can be tested, especially the electrical things.

You just have to be systematic and logical.

James

I want the above post to marquee across the top of the screen on every tech forum on this site.

Perfect example, yesterday I had an E39 with a non-functional horn and radio. I couldve thrown a horn relay, a swtich, and new horns at it and fixed nothing. But being 'systematic and logical' I traced the problem to a faulty ignition swtich with a dirty connection sending only about 4v to the horn relay which is not nearly enough to trigger it.

Moral of the story is throwing parts at it is never a good idea.

[Nathan]

Just so no one is making a mistake... I am testing the circuits and going about this in a logical manner... I had extra parts and in order to eliminate them as cuases, since it is more likely to be a bad relay/fuse/switch I switched them out. I've now come to the conclusion that those are not the source of the problem, so I've started testing circuits and wiring. I've asked for some help and haven't really gotten any insight. Now I will ask again, has anyone encountered and fixed a similar issue? What are some other likely culprits with this sort of issue?

Thank you Tom for you offer of help, and that is certainly a possibility.

[arsevader]

Re: Low Beams don't work...

So i'm getting very anoyed with not having my low beams working. The low beam check light hasn't come on at all since they stopped working.

Have you checked the low beam check relay? It's actually part of the fuse panel circuit board and I believe may cause the problem you are having.

If I remove fuse 17 the drain reduces by .2 volts but since that fuse handles a ton of stuff that is hard to pin down.

You need to check current drain using an ammeter in line with your battery. Current drain is measured in Amps not volts. And by my info, fuse 17 just controls sunroof and power windows.


James

[Nathan]

Your right, I ment fuse 21.

I'm not sure how to test that relay... The manual lists tests for the external relay sockets but doesn't say what it means if something is wrong. The table is on page 15:34 of the Bentley Manual and the tests "30 and ground" for the high beam and low beam relay sockets is the one that neither relay socket passed.

[arsevader]

Your right, I ment fuse 21.

Big culprits here would be glovebox light or trunk light. You still need to check the current drain with an ammeter though.

I'm not sure how to test that relay... The manual lists tests for the external relay sockets but doesn't say what it means if something is wrong. The table is on page 15:34 of the Bentley Manual and the tests "30 and ground" for the high beam and low beam relay sockets is the one that neither relay socket passed.

Your high beams work though? When you tested the low beam relay socket, did you plug in the high beam relay while you were doing it?

It does sound like the low beam check relay is the problem. Especially seeing as your check panel light doesn't come on. This relay is part of the circuit board in the fuse box so you'd need to replace the whole board. Try and find one at a junk yard.

James

[Geez Tech]

Checking the basics goes a long way, it is always good to actually find the problem whether it is a power supply problem or a compenent problem.
I help many others at a different site and too many people run out and spend $$$ on things they dont actually need because they didn't bother to test anything first or they do a bunch of repairs to only have the same problem.
Good trouble shooting is the key, along with good listening skills.
Unfortunatly, too many have just enough knowledge to be dangerous, that is when a shop is good to go to before the end result is a tow bill and big $$$ to straighten out the car.

NOTE: I'm not referring to Nathan, this is just in general and it takes some of us to see through the smoke and get good info to help others.

[Nathan]

Your high beams work though? When you tested the low beam relay socket, did you plug in the high beam relay while you were doing it?

Yes, for when I tested 30 to ground. It says to temporarily insert the High Beam relay for that particular test.

Thanks for the help. I will probably go to a junk yard and look for a new board within the next couple days.

And having the voltage drop on fuse 21 makes sense since I had my trunk open and therefore my trunk light on when doing the testing.

[kylebes1]

I had this problem and solved it. I cannot remember exactly how.

May sound dumb, but I think it had something to do with the high beam. one of teh posts was damaged. the high beams worked though.

unplug your igh beams and try that. cannot really remember. also check all your other bulbs outside....