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R129SL
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Discussion Starter #1
I started having a problem with the ASR system on a 1992 500SL. I was driving on the highway when the ASR sensor light came on and the car defaulted to a "limp home mode": The engine output power was reduced and I was able to make almost home; after stopping at a red light the battery light came on and the car completely stalled. I restarted the car and the ASR light was off and the car drove normally home.

Two motors relating to the ASR system were replaced by the service shop: ($ 1,500 Parts & Labor). The car was running fine for three months then the ASR problem returned. The repair shop then replaced the ASR sending unit: ($ 680.00 Parts & Labor). A week after the sending unit was replaced the ASR problem continued to occur sporadically. The shop then installed a brand new electrical accelerating unit (a very expensive piece of computer hardware: ($ 2,000 Parts & Labor) in the hopes that the computer was causing the ASR sensor program to trigger in error, but the problem continued.

The original electrical accelerating unit was reinstalled and I was credited for the
cost of new computer module; thank god. The over voltage protection relay was also tested with a new unit but the problem persisted. The repair shop has been testing the car for the last few days and the problem has not returned.

Has any one experienced problems with the ASR system similar to mine?, and what information could you provide. I am concerned that this is going to be
one of those problems that will haunt me for a while.

I use a very good repair shop that specializes on Mercedes repair. I am thinking of taking the car to the dealer if it happens again, they may have
better diagnostic tools or more experienced repair technicians. So far I've spent over $ 2,180 just on parts and service.
 

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'00 ML320 Elegance
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8,965 Posts
Yikes...

I use a very good repair shop that specializes on Mercedes repair. I am thinking of taking the car to the dealer if it happens again, they may have
better diagnostic tools or more experienced repair technicians. So far I've spent over $ 2,180 just on parts and service.
Sounds like it is a good idea to take it to the dealer in this case, as they may also have service bulletins on this. Who knows, they may even be willing to goodwill part of the repair costs.
 

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SL500
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56 Posts
Go to the dealer...

Your original problem sounds more like a low voltage problem, and not an ASR problem at all. I'd go to the dealer for this sort of problem. The ASR system has a tester that the dealer can read out to get the fault code. (In addition, I'm not aware there being two motors related to the ASR system... only a hydraulic control module.)
 

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2000 ML430
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12 Posts
ASR MIL

I recently purchased a 97 SL320 that had an ASR fault and the problem was a relativley cheap brake switch. In my case the givaway was that both the ASR and the ABS lights were on as the ABS will only work if the brakes are depressed and the ASR will only work if they are not. All the wheel speed sensors checked out fine. If you are experiencing any ABS issues in addition to ASR, either the brake switch (separate from the brake lights)or one of the speed sensors could be intermittently failing.

I have also seen a few threads with regard to low voltage causing similar problems which could be weak charging issue. If so the problem may be more prevalent with a lot of electrical load (fan, heated seats, headlights, etc.)
 

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500sl
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3 Posts
ASR Problem

Had same problem with my 91, 500sl. Would go, into limp mode at most inopportune times. My solution was not as complicated as you listed. My prolem was related to the accelorator linkage. There was some slack because a plastic fitting around the cable was broken. Something about the computer misreading throttle position. Check the end of your thottle cable for slack. Fixed it and never had the problem again.
 

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RE: ASR Problem

want to check out the brake switch on my car to see if it is going to clear my asr and abs fault but are we talking about the brake switch on the brake pedal?
i know that sounds bumb but it could be the foot brake one or some other.

just want to check.

what is replacing it like?

dave
 

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5 Posts
chipstone said:
I started having a problem with the ASR system on a 1992 500SL. I was driving on the highway when the ASR sensor light came on and the car defaulted to a "limp home mode": The engine output power was reduced and I was able to make almost home; after stopping at a red light the battery light came on and the car completely stalled. I restarted the car and the ASR light was off and the car drove normally home.

Two motors relating to the ASR system were replaced by the service shop: ($ 1,500 Parts & Labor). The car was running fine for three months then the ASR problem returned. The repair shop then replaced the ASR sending unit: ($ 680.00 Parts & Labor). A week after the sending unit was replaced the ASR problem continued to occur sporadically. The shop then installed a brand new electrical accelerating unit (a very expensive piece of computer hardware: ($ 2,000 Parts & Labor) in the hopes that the computer was causing the ASR sensor program to trigger in error, but the problem continued.

The original electrical accelerating unit was reinstalled and I was credited for the
cost of new computer module; thank god. The over voltage protection relay was also tested with a new unit but the problem persisted. The repair shop has been testing the car for the last few days and the problem has not returned.

Has any one experienced problems with the ASR system similar to mine?, and what information could you provide. I am concerned that this is going to be
one of those problems that will haunt me for a while.

I use a very good repair shop that specializes on Mercedes repair. I am thinking of taking the car to the dealer if it happens again, they may have
better diagnostic tools or more experienced repair technicians. So far I've spent over $ 2,180 just on parts and service.
I have had exactly the same problem getting worse over 4 years. No one can find the cause. What fixed your car in the end?
 

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1991 500 SL, 75K, DlyDrvr
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62 Posts
ASR Problem

Chipstone,
The brake light switch is on the brake pedal and is simple to replace. Just take your time and all will go smoothly. I had similar ASR/LH problems and after replacing the brake light switch, (not the problem) checking codes, (there are no codes for the ASR light) I finally took it to the dealership. The way they check the ASR problem is by asking the customer just what has happened recently since the problem started (this is what my dealership told me as there are no codes for this). Everything pointed to the Electronic Accelerator Actuator (that checked out okay as well). After discussing the past few months with the car, we established that my problem was moisture in the R25 sensor (throttle positioning sensor) causing the ASR light to come on and the engine to go into the LH mode.
The moisture came from power washing the engine and water got into the sensor because the protective covering around the wire harness had deteriorated. They recommended just driving the car until the built up heat dried out the moisture in the sensor. It worked! Hope your fix is as simple as this as there is nothing quite as frustrating as spending money on parts/labor that does not cure the problem. SpeedDemon
 

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ASR Problem

I have a similar problem on my 94 320. Seems that both SRS/ASR light come on together when the car is started cold and stayed on until it warmed up and I re-started it. The lights atayed off. I checked the battery voltage when the car sat for a couple of days and found 12.2 volts. I've charged the battery and disconnected it for the winter. Will conncect and try again. I only mention this because the under voltage condition seems to possible be my problem. Hope so anyway. I did replace one front speed sensor that the mechanic said was bad. Not sure that is was a problem.
 

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1995 Mercedes Benz 500 SL Convertable Coupe
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35 Posts
Asr

Funny I was reading about this just yesterday. This may sound like a simple solution. But, both front and back tires should be the same size. If not this could be the cause. There is a sensoe that can detect if the back tires and front are not in sink. It said that there is like a 15mph leeway. If you have an oversize tire in back and a regular one in front. This could be the problem.

If they are the same size. Then just ignore this, LOL :thumbsup:
 
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