Warning Lights on Dash - PeachParts Mercedes-Benz Forum

sjh · #1 03-15-2011, 10:49 PM

w124 - '90 300D - turbo.

I'm driving to work. All is well. I park and go inside. I come out 3 hours later and turn the key. None of my dash warning lights come on except the SRS and ABS on the right side. None of the lights on the left side will light.

As best I can tell the warning lights still function, they just don't display a self-check when the key is first turned on.

Any advice?

vstech · #2 03-16-2011, 12:13 AM

which position? 1 click, 2 click or starter position?

compress ignite · #3 03-16-2011, 02:10 AM

Electrical (Contact)Portion of the Ignition Switch.

OR

Ground,Left-hand I.C.

sjh · #4 03-16-2011, 10:44 AM

Quote:

Originally Posted by vstech

which position? 1 click, 2 click or starter position?

When turned to position 2, the position where the glow plugs are warming and normally all of the idiot lights are illuminated. Before going to work the system did the normal self-check with the key in that position.

Quote:

Originally Posted by compress ignite

Electrical (Contact)Portion of the Ignition Switch.

It is only the bulbs on the left that don't light. The ones on the right, glowplug/SRS/ABS do function properly.

Any thoughts are appreciated.

Jeremy5848 · #5 03-16-2011, 12:56 PM

Can you confirm that the fuel reserve light also doesn't come on (since it is on the left side)? While in self-check/preglow mode, you should be able to test the turn signals and the dash lights; do they work? Does the high-beam indicator work when you pull on the stalk to flash the high beams?

The bulb self-check is powered through the alternator circuit and fuse 5. I would first check fuse 5 and then pull the cluster so you can wiggle the big 15-pin round plug to see if you have a bad, loose, or corroded contact. While you're in there, make sure the charge indicator bulb hasn't failed. If it fails, it may knock out the test circuit. Finally, check for proper operation of the charging system with an ammeter or voltmeter.

Jeremy

sjh · #6 03-16-2011, 01:55 PM

Quote:

Originally Posted by Jeremy5848

Can you confirm that the fuel reserve light also doesn't come on (since it is on the left side)? While in self-check/preglow mode, you should be able to test the turn signals and the dash lights; do they work? Does the high-beam indicator work when you pull on the stalk to flash the high beams?

The bulb self-check is powered through the alternator circuit and fuse 5. I would first check fuse 5 and then pull the cluster so you can wiggle the big 15-pin round plug to see if you have a bad, loose, or corroded contact. While you're in there, make sure the charge indicator bulb hasn't failed. If it fails, it may knock out the test circuit. Finally, check for proper operation of the charging system with an ammeter or voltmeter.

Jeremy

Hello Jeremy,

The fuel reserve light does NOT come on.

The two functions that do work on the left side are the brake indicator (fluid level - P brake on) and the bright indicator. No other warning lights on the left side illuminate.

The flashers/ dash/parking and running lights all seem normal.

Not only do the indicator lights not perform the self-check but as best I can determine they are not functioning at all.

I've not pulled the console but will.

The main fuses are fine.

Stuart

sjh · #7 03-17-2011, 05:46 PM

Well Jeremy knows the circuitry in these cars.

I replaced the alternator and everything is working as it should.

I had no indication that the charging was not occurring - EXCEPT for the failure of my left-side warning lights.

Thanks for the help.

scottmcphee · #8 11-01-2011, 11:52 PM

Hey, I'm having this exact same symptom on my 87 300D just this week. The bulb test sometimes works sometimes not, and pretty much not any more. Now, I get only the full bright ABS SRS & glow on the right side. None on the "half bright" bulbs on the left, and no fuel low indicator bulb. I know some of these bulbs do work when the functions are used later when driving (high beam, parking brake)... Just the "half bright" bulb test doesn't happen when it should (key in glow position).

Strangely related to alternator... just last night when I was driving my kids around trick-or-treating, I noticed a VERY faintly lit red BATTERY indicator. Too dimly lit to ever notice in daytime. This indicator would go out (darken to black) as soon I revved past maybe 1000 RPM. It only seemed to be doing this faint glow for less than one hour. By the end of the evening, no revs needed, the indicator was staying dark. This feels like a charging related issue.

I tested voltage as soon as I got home, engine running something just over 14 volts at idle and engine stopped, the battery tested around 12.8 volts. I will probably get a full battery and charging test at AutoZone... Cold start glow is working because it's cold here and I still get a one-crank turn start fires right up, I'm running with headlights are on they are bright, radio fine, all things electric working... been driving for a few days now like this. So if the system wasn't charging to some degree, I think the battery would be dead by now.

The only recent electric work done was having the power antenna out of the car to replace its mast, and to do that I had to remove the left tail lamp cluster (to remove plastic trunk liner).

Jeremy how is replacing the alternator to solve the issue... because this dash bulb test happens before the engine is cranked and alternator spins. Unless it was some failing PART of the alternator maybe, like a regulator, diode, or shorted winding.. causing some shorted or failing path needed to make the bulb test happen. DO you know more??

Jeremy5848 · #9 11-02-2011, 12:18 PM

I wouldn't replace the alternator without further testing and examination. Your description of the faint glow of the charge indicator and the fact that you are getting some charging suggests that the brushes in the regulator may be worn and making poor/intermittent contact. The regulator is small, inexpensive, and easy to replace on the road; I always carry a spare.

The regulator can be removed with the alternator in the car and you can also look at the alternator's slip rings (the things the brushes ride on). Over the years they get worn too. If the brushes are worn the regulator should be replaced. If the slip rings are completely worn out (less likely) the alternator has to be replaced.

The charge lamp and alternator are indeed part of the bulb self-test circuit; if they aren't functioning correctly, the self-test won't work properly. If the regulator brushes look OK or if replacing the regulator doesn't help, the problem may be in the alternator itself. A winding failure or a blown diode in the alternator is possible but much less likely than the regulator. The diodes are not separately replaceable, unfortunately.

I would also recommend checking the big ground strap between the engine and the chassis, the ground behind the instrument cluster (left side), the battery connections, and the plug at the alternator and its 3 wires.

Jeremy

scottmcphee · #10 11-04-2011, 09:53 PM

Well, yesterday the electrics started to dim, and other functions diminishing. The battery was nearly drained by the time I got work.

Lesson 1: anybody having this dash bulb indicator test issue, be warned your alternator is fading.

I bought a charger at WalMart and juiced it for the work day and that was enough to start and get home. Headlights so dim I could hardly see... but that diesel keeps on chugging with no electricity. Love it.

Observations, as your battery voltage is dropping as you drive:
1. the yellow ABS light comes on
2. after a while longer, the yellow bulb out indicator comes on
3. L/R signalling starts sounding funny and has irregular blinking pattern, until they no longer do anything

Strange enough, the red BATTERY indicator did nothing, did not come on. Yet I know that bulb works.

Fuse 5 is fine.

Charging the battery for a while takes all these symptoms away... and next time you drive, they all repeat. This is day 2 of this condition.

I know it's the alternator/regulator, I will be replacing the regulator first this weekend to see if that solves it, I suspect it will based on all said here.

scottmcphee · #11 11-05-2011, 06:31 PM

I put another regulator on (from a spares car) that had way longer brushes. I cleaned the slip rings with very fine grit (600) and brake cleaner spray while I was in there to make 'em shiny and new.

This seems to have solved the problem. Next start, all the bulb test indicators did the right thing.

I've charged the battery to max capacity.

So far, no need to replace whole alternator, just the regulator.

Jeremy5848 · #12 11-06-2011, 12:59 AM

Sounds like you got it right. Good job. Thanks for noting the list of symptoms. Note that a different car might display the symptoms in a different order, due to minor differences in the electronics from one car to another.

As you pointed out, W124 diesels keeps running even though the electrical system has failed. The 1996 and later E300D (W210) won't run without the electrical system.

Jeremy