Warning lights on!

[Boxersix]

Hi All,

Today I took my 92 500e out for a spin. I stopped at the bank and when I got back in the car and started it up all the dash warning lights except the SRS stay on. The car seems to drive OK but I did notice the ARS doesn't work as I gassed it up a bit on a corner and the tail end stepped out. I have turned the car off and on several times but the dash light still stay lit up. I looked for any burned out fuses, but they all look good.
Where should I start? I am good at nuts n bolts stuff but trouble shooting and electrics are not my game.
This car has the BurgWerks first gear start and a Wavetrac diff. The car has 210K miles on it. The trans was rebuilt 3000 miles ago. I don't know if the wiring harnesses or engine mounts have been changed.

Any help would be appreciated.

Thanks All



Boxersix

[JC220]

I think a good place to start would be to also check the 3 or 4 blade fuses which are located on top of the Base module. (As pictured) You are looking for the Black Module casing within the engine compartment. Remove the 5mm allen screws to get access into the modules within. This is at the back left of the engine compartment viewed from the front bumper with the hood up.

IMG_0608.JPG

Also - ensure all fuses in the main fuse box are recent copper / ceramic type. It is a very good idea to change all fuses within the fuse box every couple of years to ensure solid connections. You might try simply twisting all current fuses in thier holders - until new fuses arrive.

http://www.ebay.com/itm/60-piece-Cer...-/292247819916

[vatc5637]

It would seem that the logical first step would be to inspect the upper wiring harness for fraying wires leading to short circuits. Step 2 - check for error codes and report back. Hopefully in the meantime the other experts will chime in with their thoughts & suggestions. Good luck.


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[JC220]

I don't know if the wiring harnesses or engine mounts have been changed.

Yes that's true - you should try to also verify if the engine harness has been updated. (Also the ETA & Lower harness require replacement for the same reasons)

https://www.500eboard.com/forums/showthread.php?t=1784

[Boxersix]

Thanks guys,

I checked the three fuses in the CAN box - all good. I can't see any labels on the upper wiring harness. Would that mean it was OE and not a replacement? I did find a flat blade fuse that was broken. It was the one next to the main fuse box by the fire wall not the one by the shock tower. I am on my way to the parts store to get a replacement, even though I think it is a blower fuse and probably not related to my warning light issue. I'll report back once it's replaced.
Can anyone explain "Limp Home Mode" How do I know if it is activated - any warning lights to indicate the car is in limp mode?

Cheers,

[Boxersix]

I had a conversation with the previous owner and he let me know that the Upper wiring harness has been replaced, the ETA has been replaced as well as the engine mounts, so that's three of the big hitters I no longer have to worry about.

Well somehow the problem cleared itself.... I decided to drive the car to work yesterday. Even with all the dash lights on the car drove fine accept the ASR was nonfunctioning. I tested the ABS and it was functioning fine. I was showing my friend how easy this thing could light up the tires and actually revved the engine up to redline, as I backed off, I got a small back fire and all the dash lights went out and the ASR went back to normal...All is good and I still have no Idea what was going on. Whatever it was it seems to be OK now. Just needed an Italian Tune Up.....

I think I'll invest in a code reader so I can get some idea of what the free ranging electrons are doing in the electrical systems.

Cheers All,

[Boxersix]

Well the warning lights all came on again while driving to work in the pouring rain. I knew I was in trouble when the wipers started to slow down...the car stalled as I stopped in the left hand turn lane and wouldn't restart as the battery was drained. I called Triple A and waited in the rain for 1.5 hours waiving cars out of the left hand turn lane on the highway for my tow to the shop. The tech at the shop determined the alternator was not charging and the battery was shot. They installed a rebuilt Bosch alternator, new battery and a serpentine belt (old & cracked)and I was back in business ... or so I thought...

The next day I was running an errand on my lunch break and driving right by the shop and all the warning lights turned on again! I pulled right into the shop and they put the car on the lift, checked the alternator and it was not charging, I also told them the oil pressure gauge was in operable and asked them to check to see if the wire from the sender was knocked loose from the work done the day before. What they found was a bunch of wiring with no insulation!

So now I am on the hunt for a new lower wiring harness. I called the Mercedes Classic Center and Tom told me that the part was NLA. I checked the Board and saw a post that Jono was rebuilding some. I called him and he said if I sent him my core, he could rebuild it for a very reasonable price. So once it is out of the car and we see how all the connectors are we will either re-manufacture it here or send it to Jono. That should be the end of this problem.

Blue Ridge Mercedes Jonathan Hodgman
Mercedes Repair Atlanta
http://www.blueridgemb.com/

Cheers All,
Boxersix

[nocfn]

You are quite lucky you only lost the battery....

[Boxersix]

More to the story.... Once we rebuilt the wiring harness, the car wouldn't start, turns out the fuel pump relay was not getting energized. the OBD1 reader was communicating with the LE Module but no signal coming out to power the relay. My tech opened up the LE Mod. housing and found the capacitors looked a swollen/ puffy, so he is going to replace them and see if that cures the problem.

I have been having a cold first start of the morning problem for a couple of months, engine cranks but no fire a couple times then starts up and is good for the day. Only seemed to be a problem after the overnight cold soak so I figured, get it fixed when it happens more often or 100% failure as chasing an intermittent electrical problem is expensive. I'll let you know how it progresses.

Cheers and Happy New Year!

Many thanks to Jono!!!!

[Boxersix]

Hi All,
Well replacing the bad capacitors on the LH Module PC board did the trick. The car started right up. The guys took it for a test drive and let me know that it was ready for me to pick up. When I arrived at the shop, I was offered a spare fuel pump relay. When trouble shooting the no start issue, the FP relay was ordered incase the one in the car was faulty. I decided that having a spare was a good idea. I have a 911 that has the Motronic fuel injection and having a spare FP Relay is recommended as it is a common failure item. So why not have a spare on hand for the Benz. Well I stopped for gas on the way home and the car wouldn't start when I was done filling up! Crap! Now what! the starter would turn the motor over and it would just about catch and fire but not start. I nice man in a Prius offered to give me a jump... I thanked him and told him that I didn't need a jump as I had plenty of battery E juice, what I needed was fuel... I pulled the rear seat cushion thinking that maybe the relay needed to be reseated. When I touched it, it was really warm, I reseated it and still no start... Luckily I had a spare relay! I plugged in the new relay and Bingo it started right up and has been working fine since then.

So... New alternator, battery, drive belt, rebuilt lower wiring harness, repaired LH Module and a new fuel pump relay and I'm back on the road. Thanks to Max RPM Motorsports, Alex and Aaron, Blue Ridge Mercedes, Jonathan Hodgman, all the guys on the 500E Board for posting great information about these awesome (and pain in the butt) old cars that we love. I get to drive on to learn the next old Merc problem to arise. Hopefully it will be a while before I get to learn my next lesson.


Cheers All,

Boxersix

[sheward]

Thanks for the follow up. There has been several instances here lately of fuel pump relay failure and associated LH module problems. I myself replaced a FP relay some months back and recently experienced the clicking noise while driving although the engine was operating normally. I believe i may need to replace the LH module soon and when that happens i'll look into repairing the old one as you did. For now i'm carrying a spare of both items. It would be helpful to know which capacitors were replaced if you have that info.

drew

[Jlaa]

Thanks for relating your experiences and follow through to the end - not everyone does this and it is so valuable.
Do we know if there is an outfit (viktor in ny? Jono?) that will solder in new capacitors to LH modules? Also, do we know what causes the caps to go bad (puffy?)

I have a 92 WOT enriched LH in my car as well as my original 93 LH module ... Id like to fix what aint broke and sequentially replace the caps to bulletproof them over time.

Also ... to the OP - indeed, I also have a spare fuel pump relay for my own 911 .... do you know what is the part num for the 500E fuel pump relay?

Thanks.

[sheward]

Fuel pump relay part no. is 001 542 96 19

drew

[Maui]

Chris. Glad to see you got this all sorted. Did you take the car to Maxrpm? Just wondering what other reputable shops there are in the area.

One a side note, I recall last time we met your car was getting some upgrades, Wavtrac and a couple other things. Curious how that worked out?

[Boxersix]

Hey All,
There are six Capacitors on the LH Module board, And they are only rated for so many hours of use, when they die the puff up or even leak ....when you replace them it makes sense to replace them all as they are so cheap. The part numbers for suitable replacements are ULD1H220MDD1TD, Aluminum Electrolytic Capacitor - Leaded 50V 22UF 20%, & UHE1H101MPD, Aluminum Electrolytic Capacitor - Leaded 50 volts 100uF 8x11.5 20%, Nichicon is the MFG. and I bought these from Mouser.com 4 (one spare just in case) of each P/N for $3.24 plus $15.00 shipping. My friends Alex & Aaron at MAX RPM Motorsports identified the problem and the capacitors to buy and did the replacement. This stuff is way over my head and it's really good to have technicians that will go the extra mile to help out their customers. Especially with these older cars that have so may NLA parts.
Ken - I had the Wavetrac installed and all the bearings and seals replaced in the third member while they were at it. So far it seems to be fine, I still have full ASR, but I think with the Wavetrac sending drive to both rear wheels the ASR doesn't turn on as early as with the open differential. When I had all the dash lights come on and the ASR was not working, the car would smoke the tires easily. An ASR defeat switch would surely keep my tire salesman happy. I also had the headliner replaced with black Alcantera at Stitches Upholstery in Kingston WA. They did a great job for about $900. Now I need to save up my nickels to get the damage from the deer encounter fixed and also a repaint to repair the effects of southern Cal sunshine for all the years the car was in SoCal.

Cheers to all,
Boxersix

[sheward]

Great information! This may not be the only thing that goes wrong but seems very likely to be a common failure. It may prove quite valuable in the future as the supply of spares dwindles. Thanks.

drew