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Discussion Starter #1
Did the dreaded heater core and wound up with more problems than I can mention in a single thread. I finally just jury rigged the A/C heater controls to get A/C, don't care about heat. Went to drive the thing down to the tire store to get a leaking tire repaired and now the ASR light is on the throttle is in limp mode the tach does not work and God only knows what else is wrong with it. I checked pin 6 for the ASR and am getting a code 30. Problem is that I have not found anything that gives information on codes. I have found several web sites that list the ports and how to obtain the codes but fine, now that I have a code what does it mean. A thousand years ago I had a printout of all the codes but it is lost somewhere in my absolutely impeccable garage.
I did cancel the code but it came back as soon as I started it up. In the past if I disconnected the battery the system would reset but not so now. Way back, I cured the problem with the throttle linkage adjustment but that is not working. Since I got out of racing I no longer have a car carrier otherwise it would be on its way to the middle of the desert for a barbecue.
Any suggestions?
 

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2002 SL500 Silver Arrow
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fwiw - was helping another forum member with his 1995 SL500. It was an electrical nightmare. I still have a twitch from that car. His set the ASR and ABS lights at the same time and then the dash starting acting all crazy (the fuel gauge would tick like a turn signal, speedo not working, some warning lights on when the door was open, different set lighting up when the door was closed). For the ASR and ABS lights, I thought it strange that it would be a wheel speed sensor (which is what a respected MB mechanic was suggesting) since ABS is the front wheels and ASR is the rear. Not sure if that was sound logic, but I went with it. Turns out there is a number of secret fuse boxes -- one of which is on the passenger side behind (meaning more towards the windshield) of where the 38-pin plug would be. It was a metal box with a few screws. There were 4 red blade fuses in there - the one closest to the fender was blown. Replaced and fixed the ASR and ABS lights. Probably not your problem since you have no ABS light at the same time - but might be worth a look just for giggles.

As far as the dash craziness - I ended up replacing every single fuse for him -- including in the trunk -- and eventually all was well. There is also (what appears to be) a lighting related fuse box behind (again meaning closer to the windshield) the main box. There was a blown blade fuse in there as well. I never bothered to find out what that last fuse was for, so I probably fixed something I didn't even know was broken.
 

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Discussion Starter #3
The very first thing I did when I first got it running (about 20 years ago) was to replace all the fuses with the good fuses but it can't hurt to check them all again. When I was fighting the A/C control issues I checked across every fuse in the car with a test light but it can't hurt to take them all out and wire brush the terminals. When I did the heater core I wound up with control problems which I spent a couple of months trying to find and fix and I had the aluminum box with all the modules in it completely out of the car. I did check the fuses in the fuel module and all were good, which is not to say that one of them did not blow. One of those fuses controls the air meter and if it blows your fuel mileage will be cut in half or more.
I believe that all those blade fuses are for the HVAC blower motor. Mercedes over engineering, one fuse for each blower speed.
 

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R129 500 SL 1991
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1,247 Posts
ASR code 030 (no reception from EA/CC/ISC N4/1 or fault in EA/CC/ISC) from this post here
Either the EA ECU N4/1 is toast, the EA (electronic throttle) or the wiring between the two.
You have ‘94. Have the engine wiring harnesses been changed?
 

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Discussion Starter #6
I resurrected this 129 from a basket. The original engine wire loom was turning to powder and after pricing a new loom I bought $100.00 worth of color coded wire from R.I. Wire and soldered up a new loom. It has been working fine for about 20 years. I am not however going to say that the electronic throttle is not gone because my granddaughter blew one of the heater hoses at the rear of the engine and barbecued the engine. That is how this all started and it has been going down hill ever since. I do have another throttle assy. do not know the condition but it is not that hard to change. Pardon my Mercedes ignorance, ECU and EA I understand but N4/1 I don't.
 

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Discussion Starter #8
Going back to the beginning and trying to make some sense of all of this. It all started when my granddaughter was driving it. It blew a heater hose and she barbecued the engine. I found a used engine and put it in. First thing was that the low oil light would not go out and it is full of oil. Figured that the low oil light was not a critical issue and just removed the bulb. It then progressed to the dreaded heater core. Put in a new core and wound up with control issues, the blend door would not open so spent a couple of weeks attempting to figure that out. finally gave up and just connected the blend door signal tube in with the center vent door signal tube and got air out of the center vent. started to reinstall dash and all the related garbage, everything fine. Finally put all the trim and cover pieces back on interior and under the hood and now I have:

No tach, ASR light on throttle in limp mode, HVAC will not respond to the temp dial, interior lights will not respond to the door switches either side, presumably the low oil light still will not go out and only God knows what other issues will crawl out of the woodwork if I could drive it. Every time I attempt to fix something another thing breaks.The tach and ASR and interior lights? popped up after I put in all the trim which in my mind points to further disturbing an electrical connection somewhere.

All of this points to bad connections but I can make no sense out of the list. At first glance they seem to have no connection to each other but the list keeps growing.

I have been working on automotive electrical since I was in my early teens which is more years ago than I care to think about and in almost every instance when I was chasing several issues I would check the wiring diagram to see if there was a point where they all intersected but I always had the benefit of wiring diagrams. What Mercedes wiring diagrams I have managed to find are useless. for instance the HVAC diagram shows all the wiring but no internal information for the control head. If it wasn't for the fact that I gave the car to my granddaughter and she loves it I would have sent it to scrap months ago. If someone can make some sense of this mess I am open to all suggestions no matter how convoluted.
 

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Discussion Starter #9
The key word in my last post is convoluted and that is what this R129 is. I will swear it is possessed. I checked the main fuse panel and found that fuses 1,2 and 3 had no power. I said screw it I am not crawling under the dash to trace those wires so I just jumpered them, on the back side of the fuse panel. Just to be clear those fuses are for lighting; park, tail license plate, instrument cluster, fog lights, warning buzzer and headlight cleaning system. I started it up and now the blend door on the A/C works correctly. The control head responds to the temp dial. The ASR light is off and the throttle works correctly the instrument cluster is back on line. Don't know if the low oil light works and don't care. The interior lights still don't respond to the door switches but I will take what I have and be very happy. Hopefully I have fully appeased the Mercedes gods and it will be reliable for my granddaughter.
 

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1995 SL500-129
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The key word in my last post is convoluted and that is what this R129 is. I will swear it is possessed. I checked the main fuse panel and found that fuses 1,2 and 3 had no power. I said screw it I am not crawling under the dash to trace those wires so I just jumpered them, on the back side of the fuse panel. Just to be clear those fuses are for lighting; park, tail license plate, instrument cluster, fog lights, warning buzzer and headlight cleaning system. I started it up and now the blend door on the A/C works correctly. The control head responds to the temp dial. The ASR light is off and the throttle works correctly the instrument cluster is back on line. Don't know if the low oil light works and don't care. The interior lights still don't respond to the door switches but I will take what I have and be very happy. Hopefully I have fully appeased the Mercedes gods and it will be reliable for my granddaughter.
Hi Oldguy, Funny thing, I am having problems with the ASR light on and checked the fuses for power, and the ones you mentioned as no power, are the same on mine. When you say you jumped them, what do you mean and how did you do it? Is the car running all good as in no ASR light on and normal throttle? thanks, Rob
 

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R129 500 SL 1991
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❗In case you don’t want your SL to burst into flames, if you do jump fuses 1, 2 and 3, I strongly suggest the first thing you should do is disconnect the headlight washer motors. The connector plug is just behind and below the headlight units.
 

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Discussion Starter #13
Thought that I would add a post script. The jumpers are gone. The problem turned out to be a connection somewhere under the fuse box and relay center. Don't know what or where as it is too deep to reach from the top and I will burn that thing to the ground before I will take the dash out again. I have managed to position the wires where everything works properly at the present.

Ozzie Rob, Something you might try with regard to your ASR light would be the throttle linkage adjustment. I recall it being about a 10 step process. I bought mine in a basket close to 20 years ago and when I put it together I had fits with the ASR light, sometimes putting the throttle into limp mode sometimes not. Sometimes also triggering the ABS light and whatever the one is beside the ABS light. I fought it for months and quite by accident ran into the throttle adjustment procedure. I adjusted it in accordance with the procedure and it was fine for years.

If you decide to try to find and fix a wiring problem put your therapist on a pre pay plan because it will drive you nuts. There is absolutely no applicable logic to the interconnections in the wiring. As I have stated many times about Mercedes wiring, it is like you put the wrong heat range sparkplug in #5 cylinder it will cause the LR tire to go flat.

I was recently talking to an acquaintance of mine who is the #1 engine assembler, machinist and all around good guy in a local performance machine shop and his observation was, "Every time I work on a Mercedes I am impressed but not in a good way. I can find no reason for their compulsion to over engineer everything and then throw on top of that a totally unnecessary level of complexity. And why are they so enamored with socket head cap screws?".
 

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1995 SL500-129
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Hi Oldguy, You nailed it there, I have been saying this for years, the same as I said a long time ago, how or why would an automobile manufacturer supposedly the most prestigious on the planet, design a vehicle such as a super car, and stick wiring in it that falls apart creating immense damage and no safety recall. I took all the modules out and simply cleaned the contacts, now I have both ABS, and ASR lights, but it runs as normal. All I want to do is have it running good without the lights so I can sell it. I can't even get the codes cleared because no mechanics have a reader that communicates with it. Local guy has a Snap on that does and he cleared everything, and when i jumped in the car the lights were on and it was in limp mode. Huge Mercedes dealership do not have equipment that will communicate with it, and then they want $275 an hour. I had a beautiful Jeep Grand Cherokee, that I ended up almost giving away because of similar stupid design faults, Had Mercedes engine and Transmission. Never, would I own a Mercedes again. Can you clear the codes with a amp meter or a couple of wires? I don't want to read the codes just clear them.
Thanks, Rob
 

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1995 SL500-129
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I will tell you another thing. My brother owns an ML500 and no longer drives it, as it is to dangerous. His problems started a long time ago when he was scooting down a motorway when the front right hand brake jammed on and took him across the median and luckily stopped before heading into the on coming traffic. Holliday destroyed, towed back home to a Benz dealership, they changed a wah sensor think that is what it is called. Long story short, happens everytime he drives it. Why would you design a vehicle that allows that to happen, It should not happen at all. I have read some gloomy stories about this fault. Why, after all these years are people still having the same stupid problems, or still trying to correct them. Why can you buy any other powerful vehicle and not have any of these issues. Does not say much for Mercedes Benz. One last thing, why are parts so expensive for say a 1995 SL500 R129? $600 for 1 engine mount plus GST, $38 from Pelican Parts in the USA. Why the ridiculous price for a wiring loom that is a failure of Mercedes? Yet, you can buy every part from a latest model for a fraction of the price. I actually know a lot of people with Mercedes including the latest, and sware never again.
 

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1995 SL500-129
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The key word in my last post is convoluted and that is what this R129 is. I will swear it is possessed. I checked the main fuse panel and found that fuses 1,2 and 3 had no power. I said screw it I am not crawling under the dash to trace those wires so I just jumpered them, on the back side of the fuse panel. Just to be clear those fuses are for lighting; park, tail license plate, instrument cluster, fog lights, warning buzzer and headlight cleaning system. I started it up and now the blend door on the A/C works correctly. The control head responds to the temp dial. The ASR light is off and the throttle works correctly the instrument cluster is back on line. Don't know if the low oil light works and don't care. The interior lights still don't respond to the door switches but I will take what I have and be very happy. Hopefully I have fully appeased the Mercedes gods and it will be reliable for my granddaughter.
Could you let me know how to jump the wires on the back of fuses 123. I resolved the ASR and ABS lights by removing the controllers and putting a tiny piece of grease on the frame so the unit would slide in a bit better, and the ASR module went in further than before. When I started the car, no lights and no limp mode, took it for a drive around the block, and driving in my driveway, limp mode and ASR light on. I have done everything outside of jumping the fuses 123, so as much info would be great.
Thanks, Rob
 

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Thought that I would add a post script. The jumpers are gone. The problem turned out to be a connection somewhere under the fuse box and relay center. Don't know what or where as it is too deep to reach from the top and I will burn that thing to the ground before I will take the dash out again. I have managed to position the wires where everything works properly at the present.

Ozzie Rob, Something you might try with regard to your ASR light would be the throttle linkage adjustment. I recall it being about a 10 step process. I bought mine in a basket close to 20 years ago and when I put it together I had fits with the ASR light, sometimes putting the throttle into limp mode sometimes not. Sometimes also triggering the ABS light and whatever the one is beside the ABS light. I fought it for months and quite by accident ran into the throttle adjustment procedure. I adjusted it in accordance with the procedure and it was fine for years.

If you decide to try to find and fix a wiring problem put your therapist on a pre pay plan because it will drive you nuts. There is absolutely no applicable logic to the interconnections in the wiring. As I have stated many times about Mercedes wiring, it is like you put the wrong heat range sparkplug in #5 cylinder it will cause the LR tire to go flat.

I was recently talking to an acquaintance of mine who is the #1 engine assembler, machinist and all around good guy in a local performance machine shop and his observation was, "Every time I work on a Mercedes I am impressed but not in a good way. I can find no reason for their compulsion to over engineer everything and then throw on top of that a totally unnecessary level of complexity. And why are they so enamored with socket head cap screws?".
I reckon Mercedes build their vehicles like this so that all the gullible wealthy people and anyone not wealthy but just as bad, break down, and take it back to the MB dealership, and they fix it at a ridiculous cost, and being the suckers they are pay it up. Mercedes is behind Toyota in quality and, engineering. NEVER AGAIN.
 

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R129 500 SL 1991
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1,247 Posts
Check the voltage supply at ABS/ASR control module from the over-voltage protection relay (OVP). There shouldn’t be any more than 0.3 V drop between battery voltage at fuse box and voltage at pin 1 of the ABS/ASR control module. If there is replace the OVP.
 

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Discussion Starter #20
Now, just drove 10 kilometers, and it is now in limp mode.
Ozzie Rob, does your '95 still have the round 38? contact test plug? If so you can make a really simple tool to check codes out of a cheap led. Do a forum search on posts by bobterry99 and you should be able to find it. A breakdown of the test plug is readily available with a google search as is the list of codes. Problem is that the code explanations are written in germanese which is similar to legalese but more convoluted.
With regard to your particular issue have you checked the 10 amp fuses in the rear most module in the box by the RH hood hinge. The fuse closest to the right side seems to have an effect on the ABS/ASR. There are also two fuses in a relay that possibly controls the phases of the moon, don't know. It is about an inch square with a clear plastic top. there are two fuses in it that also can have an effect on the ABS/ASR. Some are in the same electrical compartment by the right hood hinge, the pictures I have seen it seems to just be floating around in there. Mine ('94) is in the compartment behind the fuse box.
However what you describe sounds like the issue I was experiencing when I originally put mine together and it was simply a matter of properly adjusting the throttle cable/linkage adjustment.
That also is somewhere on this forum, would attach it to the post but I am old, do not understand computers and don't know how to attach images here.
If you get in contact with me, I believe that it is possible through the forum, I will send you everything I have. I do know how to attach a file to an e mail.
 
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