More grief with the ABS light + Poor idle - PeachParts Mercedes-Benz Forum

tinypanzer · #1 05-06-2009, 04:22 PM

Well, I put a new voltage regulator on, and that seemed to have cured the issue. 1K miles with no ABS light.

Today was another story. The ABS light is now coming on for extended periods of time (at least 5 minutes sometimes more).

While the ABS light is on, my idle gets VERY poor, hovering around 450 when in drive, and almost stalling. In park or neutral it climbs back up to 700 but still idles roughly.

I managed to get my meter on it while it was doing this behavior and I found my system voltage to be 13.5 at idle, in neutral.

As soon as the light goes out, my idle returns to normal and my engine power comes back.

Any ideas???

pawoSD · #2 05-06-2009, 04:34 PM

The type of car is?

13.5 is slightly low, but still normal/charging.

tinypanzer · #3 05-06-2009, 04:54 PM

Sorry, it's a '90 300SE.

Recent parts replaced:

OVP Relay
Voltage Regulator
Battery about 1 year old
Fuel pump, filter
All fuses

Thanks!

tinypanzer · #4 05-06-2009, 06:18 PM

UPDATE -

I let the car sit for a few hours and restarted it. It barely wants to start, and the ABS light is now on solid.

WTF?? Help!!

tinypanzer · #5 05-06-2009, 06:34 PM

I'll be damned -

Just on a hunch I decided to pull off my brand new OVP relay and put my old one back on (luckily in my trunk) and the problem went away immediately, the car started right up, held a smooth idle at 800RPM, and system voltage went back up to 14.

How's about that - a brand new defective OVP relay!

Just goes to show - new doesn't mean good.

duxthe1 · #6 05-06-2009, 07:48 PM

I didn't follow up on your last post but I see that you found and fixed the charging problem. Reading through this post I was thinking that you need to check the OVP relay again. It's a good thing you held onto your old one, eh? Defective new parts are a *****.

The worst one I remember is a new distributor cap that was installed on the president of the local Mercedes club's S320 . Went all of a mile and a half and completely failed. Missed being able to deliver the car when promised b/c of all of the time spent checking everything else first.

tinypanzer · #7 05-06-2009, 08:08 PM

I'm beginning to wonder if in fact I even had a charging problem before. I think now it was just the OVP beginning to fail.

All in all, I needed to replace the voltage regulator anyway, since it had over 120K on it. There was only about 1/4" of brush left......

This brings me to another question - What the hell is the OVP doing when it does this kind of thing? Is it trying to dump "excess" voltage via the zener diode, or what? Odd that the car will still run, just so incredibly poorly.

I wonder if it caused my old voltage regulator to finally give up by dumping voltage and overloading the regulator......

I just dunno...... At least I'm getting home tonight, and at least it waited for my mom to give me the car back before doing this.

pawoSD · #8 05-06-2009, 08:30 PM

Were the fuses in the new OVP intact?

duxthe1 · #9 05-06-2009, 08:37 PM

What you were describing sounds like the OVP going open circuit and not supplying any consumers with power. The poor running and idle were due to the car running without any electronic assistance. The fuel injection is mechanical and can supply fuel without the CIS module being online.

tinypanzer · #10 05-06-2009, 08:39 PM

Aaaahhhh! I see now. That makes sense!

Thanks for the explanation.

Yes, both 10A fuses were intact!

"The fuel injection is mechanical and can supply fuel without the CIS module being online."

That is totally cool that it can run without its brain, albeit quite poorly..... I've always heard that it could do that, but never really believed it. Well, I just drove to the airport and back with no brain and I made it. Wow....

Ivanerrol · #11 05-06-2009, 09:18 PM

This new OVP you bought. Was it OEM or an ebay special?

How are the contacts where you plug the OVP in - nice and clean?

tinypanzer · #12 05-06-2009, 09:21 PM

Yup, the contacts were good. I even opened the plug and inspected the solder joints.

No, it wasn't an Ebay special, I ordered it from FastLane! It's an APA. Guess I should have gotten the Kaehler!!

Ivanerrol · #13 05-06-2009, 09:38 PM

My spare parts specialist at the local stealership informs me that the OVP and FPR's were upgraded with redesigned electronic components many times during the period that these were produced as a new item.

The latest upgrade is the item you should be putting in.

I bought an OVP from a non OEM spare parts specialist. It had no markings on the outside and had been made in China. I like yourself ended up putting the original OVP back into the car until I ordered one from an OEM Benz part supplier. The cost difference was over $ 100.00.

I.M.H.O. The OVP and FPR are critical components for the KE system. When ordering parts from Fastlane specify the OEM component.

J.HIDALGO · #14 05-06-2009, 09:52 PM

are typical (in my limited experience) of a bad OVP. I hope other people read this thread and try the OVP first. I know the OVP gets blaimed for a lot of things but, this is typical.
I am glad you found the problem...

tinypanzer · #15 05-11-2009, 10:53 PM

Upon examining the defective OVP closely, I discovered that the contact for one of the fuses had burned up. Not on the fuse itself, but the contact in the socket. I was able to see it through the discolored plastic slot........ FYI......