ASR and ABS light on intermittent.
 

I just had my 1991 500SL Motor mounts replaced, in the process some flaky wires were broken and the ASR light only came on, and the car went into limp mode. The shop replaced the wiring and now intermittently the ASR light AND the ABS light go on, if I restart the car it usually goes away.

The shop said they replaced the overvoltage relay but the numbers did not match, they called 2 mercedes dealers who said the non matching relay was the right one, and the original one was discontinued. The original relay had only one fuse, while the second one had 2 fuses. The shop thinks the new relay screwed something up and put in the old relay and told me to drive it for a couple of days. It still lights up ASR and ABS intermittent, although it does NOT go into limp mode.

Anyone have any clues?

By the way the ingnition switch is starting to go bad. Every once in a blue moon when the key was cycled only the SRS light goes on, it cranks and wont start. Cycling the key eventually produces all the dash lights and it starts no problem. After the motor mounts were put in this ignition switch problem changed from once in a blue moon to constant, so Im not sure if they are related or if, as the shop says, they just finished the switch off since they used it a lot in diagnosing. The switch is $1500 to fix, sigh.

$1500 for an ignition switch??? On what planet? The only way I could remotely imagine replacing an ignition switch to approach that price would be if it wouldn't turn at all and they had to sit there for 8-12 hours with a drill to drill it out ...


The tumbler and new key is about $75; I don't know how much the whole switch is but shouldn't be THAT bad! I would start there, personally, since it is fairly obviously bad and you need to replace it anyway. It MAY solve your ABS/ASR light problems. If not, need to have the codes pulled. This symptom can be caused by MANY different problems (like a faulty $15 brake switch in my case).

Good luck!

The early SL's require the updated version of the ignition switch. It involves more than just a key and tumbler. Still $1500 sounds pretty darn high!. I'll check at work to see how much it should cost and post tomorrow.

From what I gather the switch itself is about 1000 bucks and there is a ton of labor involved. This same mechanic has done quite a bit of work to it already and is quite fair, always undercutting the dealer by quite a bit. I still have to call the dealer to get an exact price, but usually expect the run around with them.

Incredible! Must be some switch!

Have you checked with Phil at FastLane (assuming your mechanic will let you bring outside parts for him to install)? Under these circumstances I'd shop around as there may be a BIG difference in price from one source to another.

With regards to the switch, it has not done it in 2 days, very very weird stuff. At least I can hold off on it.

With regards to the ABS/ASR lights I have done an exhaustive search on the forum and so far it looks like the likely culprits could be:

brake lamp switch
battery
alternator
overvoltage protection regulator
wheel sensors
faulty wiring harness

When it was at the shop they checked the alternator and said it was ok. I did replace the battery with a brand new official MB one, and replaced the brake lamp switch. The shop had tried to replace the overprotection relay but like I said, the part MB gave them was a different number and had 2 fuses instead of one, so my mechanic put the old one back in. When I spoke with him today he still seemed to think the overprotection relay was somehow at fault, but the lights go on with the old one and the new one, hmm. He still thinks it may be the wiring going to the OVP.

While he had it in the shop he did replace the ASR wiring harness, but not the main ECU harness. He also did the rear brakes and says the wheel sensors are OK.

After installing the battery and the brake lamp switch the lights dont seem to go on, but I have only turned it on 2 or 3 times since then and the lights are usually intermittent. When they do go on they go on for the next 10 or 20 car starts, then go away for the next couple of hours, weird, almost like a pattern.

OK techs/guys, can anyone further pinpoint what it may be? I would replace the overprotection relay but am hesitant (and so is my mechanic) since the part has 2 fuses and a different number. MB says the original one was discontinued and to use that new part, any thoughts on this?

Thanks much.

ASR/ABS light shows
 

Sounds like the well known defective wiring insulation in the main harenss and/or the electronic throttle actuator. Both are known problem areas. Real ***** is the intermittent nature at first, and then the horrible fact that even more expensive 'computer boxes' can be fried with the wrong short.

I have a hard time accepting the 'faulty ignition switch' thing.

Have fun.

I thought I had the problem licked with the brake lamp switch and new battery, the lights had not gone on the whole day. Yesterday leaving the gym, on starting the ASR/ABS lights went on, I restarted twice and they went away, and have not come back since.

I bet it does turn out to be that stupid wiring harness. From what I gather its like 3k to replace it.

Update:

Still no sign of the ASR/ABS lights, (knock on wood). I know they will pop up eventually, but Im hoping against hope.

Still no one with any idea what this might be?

spincedoc,

What was the end state of this thread? Fixed or not and what was problem?

I had the same intermittent ASR/ABS lights. A search here pointed to the brake light switch. Turns out, that's exactly what it was.

Which break light did you change?
 

Hi Larry, My 1993 190E seem to have a similar problem, its brake light (the symbol circle with hyphens around it) glows fainly as I drive it around. could this be down to the hand brake swith too?

Nope -- that's the signal that your front brake pads are worn and due for replacement. That info is in your owner's manual -- if you don't have one, call 1-800-FOR MERC and order one...

Just to close up my problem at least, the shop replaced some wiring related to this, they saw lots of dried up disintegrating wiring in this area. I have since sold the auto and purchased a 96 SL500. After the work was done the lights did not come back on again.