lvjeff

I went to the couple of junk yards in town recently and there was only a single 90s SL and the OVP was already gone , ill keep my eye out on ebay for a recent used one. This weekend im going to test the newer brake wire harness i have on the driver side and see if it clears the abs light.

dolucasi

Looks like all W201, W124, W129's have the same OVP part number at least for the 89-90 period. So your donor pool is larger than previously believed and you can check other models as well.

lvjeff

oh that’s good to know I’ll look around for those as well

lvjeff

@dolucasi A new data point for the ABS light issue. I tried to replace the driver side brake wiring harness but it looks like way too many important things have to get pulled out or moved (the fuse box area, master cylinder and brake booster etc) I dont have the confidence to do that on my own. So I planned on taking it to a local indy benz specialist here in vegas to get it properly diagnosed.

Before I did that I wanted to perform an experiment where i compare driving with the front left abs speed sensor connected and not connected. With it plugged in drives like normal plus after about 30 feet of driving forward the abs light comes on. With the sensor unplugged from the harness what a crazy difference! the car accelerates so much better, idles much smoother (i didnt think it idled bad before) and the ABS light does not come on no matter how far i drive. I also cant get it to stall anymore. What is going on here? Is this pointing to the new speed sensor I installed being bad? (Its not genuine MB) Or the left side brake harness is bad? What does it mean to not have one of the speed sensors connected? Im still planning on brining it to the shop but would love your or anyones take.

thanks
jeff

dolucasi

Here is my take assuming that the brake wiring harness you mention is the actual wiring connecting the ABS speed sensor to the ABS unit.
And you are having a hard time replacing the wiring harness. Please confirm this.

If so, I think my previous assertion earlier in the thread may well be correct in that the driver front is the master. If you disconnect it perhaps the ABS speed check can not be performed properly.
No matter what though it seems the aftermarket speed sensor may be a culprit. Do you have the original sensor? I assume you replaced that hoping the ABS light will go away? And it did not.

BTW, all this is way premature for your car. My OE originals are still in the car at 200+Kmiles and I have no issues. I also have not read very many comments on ABS issues on well taken care of cars like yours.

Perhaps the specialist can figure all this out.

lvjeff

HI

Ya the harness section is the separate harness section that connects the speed sensor and brake pad wear sensors to the abs and car. But not connecting the speed sensor was also a red herring, while on an initial drive from cold the ABS light did not come on. If I drove around for a bit then shut the car off and then started it back up the ABS light would come back like normal. Looks like im going to just leave the ABS stuff for the indy shop.

Another question for you @dolucasi i saw a post you had a few years ago on benzworld about changing your manual transmission fluid to ATF from gear oil. Im planning on doing that with my manual this week. Has the ATF fluid been good for you? Would you still recommend it or something else?

thanks again

dolucasi

The ABS system will do a "check" upon power up. I assume part of the check is to make sure the sensors are connected and the expected input is there. This all happens when you first turn ignition on.
So if you disconnect it after this check, you have bypassed that portion on the check. This is probably what happened to you. And after you restarted the car the check flagged that you have a non-operational sender from the driver's front.

Yes, I am not sure if the 2 manual transmissions (W201/W129) are similar, most likely yes, as far as the syncro's are concerned.

Dealer always put Penzoil ATF in mine. When I had a mechanic put gear oil in it unknowingly it became very hard to shift in cold weather.
So I put ATF fluid in as advised there. It made it very smooth but I feel it is a bit too thin. Most friends use Redline-MTF instead. So after I service my transmission I will switch to Redline-MTF.

For you, I would recommend Redline-MTF.

lvjeff

Appreciate it thank you, im hoping to get in with the indy shop next week, ill post what they say.

lvjeff

Hey @dolucasi I have an update about the mysterious ABS light. My local indy shop figured it out, It was the front passenger side sub harness with an open circuit. The harness that is between speed sensor and the controller. The controller would trip the light when it got only 1 signal from the driver side. I was fixated on it being the driver side problem since spinning that wheel would trip the light and spinning the passenger side didnt. I should have known the controller would need both signals to determine everything is fine.

dolucasi

Great to Hear Jeff. Any other issues with the car now?
Happy motoring!

lvjeff

so far so good, I tested abs on a gravelly road and it kicked on correctly when i expected it to. i recently changed the fuel pumps (they were original) and i havent seen the stalling issue i was seeing intermittently when pressing the clutch and letting the revs fall to near idle so maybe one of the pumps was on its way out or both were going bad.

dolucasi

It's great the ABS issue is behind you. And the fuel pump replacement is a good preventative measure as it was aged. I am skeptical it will fix your random stall as when they start going bad the symptoms are quite different. But if it fixes the random stall during clutch action do post it there as the more we know the better we are informed.

Happy motoring Jeff!