Engine Electrical issues - OVP relay and voltage regulator? 1989 190D - PeachParts Mercedes-Benz Forum

tuxbeej · #1 10-05-2007, 02:39 AM

Greetings, eh?

I'm driving a 1989 190D 2.5 automatic. I love the car, but some of these problems are getting on my nerves.

During a 3100 km road trip in August from Edmonton, Alberta to Vancouver, BC, then through Penticton, Grand Forks, Cranbook, Banff, Calgary and then home to Edmonton, the car did a lot of climbing and descending mountain ranges. On the way to Vancouver, my ABS light came on and hasn't come off since.

My SRS light comes on (and the tachometer fails) intermittently. It's been doing that since March 2007. After searching this forum, I learned that the infamous OVP relay could be to blame. I didn't actually take it out of my car until the ABS light came on. However, I've tested it using a digital multimeter and a 12VDC 1.5A AC adapter with alligator clips on the end of each line. I've managed to get the relay to "click" when I bridge +Ve across pins 30 and 15 (with -Ve on pin 31, IIRC). Continuity was there and I managed to see volts appear across all of the pins. Some were showing 16 V, some were showing 8 V. I tested the fuse for continuity and it was still working fine. I unplugged my adapter, waited, plugged it back in, and tried everything again. At that point, I couldn't get the other pins to show volts at all, and I didn't hear a click when I completed the circuit.

I popped the relay back in the car and it's gone back to being intermittent again. Sometimes the tach's working, sometimes it's not (the ABS light is still always on). I can live with this for a bit, but the next problem seems to be much bigger.

The car is now idling around 500 RPM. It has been slowly dropping in the last few months. Recently, I've taken to nudging the accelerator just a tiny bit to get it up around 650-700 RPM and I don't actually take my foot completely off the pedal when I brake. At a stoplight, I usually brake to a stop, then shift to Neutral, and nudge the accel. so that I don't shake the car to pieces.

I noticed recently that before I turned the car off (after 30 minutes of driving), I turned the headlights off and the idle improved slightly. VERY slightly, but I could still hear it. Once I got home, I decided to check the battery with the multimeter.
- tested battery when off - 12.35 V on avg.
- tested battery while idle - 13.6 V on avg.
- tested battery while idle w/headlights, fogs, max fan, heater on full, and hazards - 11.96 V on avg.

So now I'm thinking "voltage regulator". Like most of us, the cheap, correct fix appeals to me more than the expensive, incorrect "fix" (which fixes nothing). Any insight to my problem? Should I replace the VR first, then the OVP relay?

PS: I took it to one of the dealerships here in Edmonton in March and they recommended replacing a *ton* of parts; parts + labour were going to work out to CAD$19,000. I've since done some of the work myself, and some through a mechanic friend. The dealership, though, recommended changing out my throttle links (among other things). Could that be another reason why my idle is getting lower - a loose or worn throttle link?

If you need more details, please let me know. I'll be more than happy to tell you all sorts of crazy stuff. Thanks, everyone.

tuxbeej · #2 10-05-2007, 02:49 AM

I should also add that my cold oil pressure is 3 bar (after I rev the engine past 500 rpm when I first start the car) and my warm oil pressure is about 1.5 bar.

I'm due for an oil change as well.

Here's more fun, and yes, I realize how stupid this is. When I had my oil changed at Mr. Lube, they weren't exactly sure where the filter was or anything like that. They eventually found it and I directed them to use 6.5 L, since that's what's recommended. When they poured in 6.5 L (of the 8 L I provided to them), they said that the stick was still showing a low level, so they wanted to add another .5 L. "Go ahead, I suppose," I said. Gradually, that became another .5, then another .5. Then all 8 L were in my car.

The car still drives fine with 8 L in it. Some of it may have burnt off or leaked or something, as the oil level has dropped a little. There is a fuel leak on my injection pump, similar to the one described in the DIY articles area (eventually, I have to get the replacement rings for that, as well as the splined socket, and perform that job).

Finally (and this might be scary), I want to do the next oil change myself. To show how inexperienced I am with this, though... which way does the oil pan plug come off? I've been trying to ratchet it off counter-clockwise and I've had no luck so far. Is it clockwise instead? I'm worried that at the last visit to Mr. Lube, they overtightened the bolt and I'm going to need an air ratchet to get it off.

I'm sharing all of this in the same thread, simply because I'm hoping that more information will lead to a really good solution. Ask me for more details; I'm not shy.

Thanks again, everyone.

JimFreeh · #3 10-05-2007, 07:01 AM

Your loaded voltage while running is low, the alternator regulator can be replaced independently of the alternator. Just a couple of fasteners and unplug it. Try that first before condemming the alternator.

Jim

tuxbeej · #4 10-09-2007, 04:41 PM

I just replaced the voltage regulator over the weekend, and I'm getting much better voltage to the battery.

With just the engine idling, it's ~14.01 VDC
With lights, CD player, heater, fan, hazards, etc, it's ~13.8 VDC.

This is a great deal better than before. The posts on the old VR were worn down almost to the white casing. I'm going to check the voltage again in about a week.

The OVP relay still hasn't gotten any better. I can still hear a lot of clicking behind the dash on the psgr. side, and I keep losing my tachometer (and the SRS light comes on).

I'm going to replace the OVP relay in the next week or so, once it gets shipped in. And then I have to figure out why the ABS light always stays on, whether the tach is working or not. I haven't felt the ABS 'kick' when I brake for a while, so I'm pretty sure it's non-operational. Whether that's a relay or the computer, we'll have to see. If anyone has any tips, I'd *love* some advice.

Thanks again!

tuxbeej · #5 10-13-2007, 04:20 PM

Just popped in my new OVP relay today and the car runs beautifully. The RPMs are sitting between 5000 and 10000, and I haven't had the tachometer failure yet during my 30 minute drive home. I think it's fixed.

I still hear a lot of clicking coming from the right dash, so I'm assuming it's the new OVP doing its job, or there's another relay back there really getting hammered.

The only other problem is that my ABS light is still on, but I'll be hitting the forum to see what other people have tried. I'm hoping it isn't connected to the brake pad sensors - as far as I know, all of my pad sensors were removed when I last got my brakes done (some were broken), and I didn't bother to buy new ones. But hey - if it's the sensors, that's cheaper than buying a new ABS computer...

JimSmith · #6 10-13-2007, 04:45 PM

Glad to see you are making progress. The oil plug is a normal right hand thread. You turn it counter clockwise to remove it. Buy a replacement from the dealer as they stick quite often, and I have rounded them off on my 190E 2.3-16 a number of times. I now use a tool that sucks the oil out of the dip stick tube.

The oil filter and oil change together should take the full amount of oil the manual calls for in an oil and filter change. If you overfill the oil, you are looking for trouble. Too much oil is bad for the engine as the crank acts like a wire whip in heavy cream, turning the oil into a foamy froth that has none of the properties of the oil alone, leading to overheating and damage to all the wearing surfaces. Like bearings. Not a good idea.

The OVP is not supposed to be popping off all the time. You may have another problem with a short somewhere or another relay is being energized in the vicinity. The KLIMA relay for the A/C is in that vicinity on a 190E, so you may want to check the climate control settings. The ABS issue is likely a bad sensor or a dirty sensor. These can be cleaned and if that doesn't work, you might try replacing them. Not sure if I have ever heard of an ABS computer going bad. Good luck, Jim

tuxbeej · #7 10-13-2007, 04:57 PM

Quote:

Originally Posted by JimSmith

The OVP is not supposed to be popping off all the time. You may have another problem with a short somewhere or another relay is being energized in the vicinity. The KLIMA relay for the A/C is in that vicinity on a 190E, so you may want to check the climate control settings.

You know, I have *never* been able to get my A/C to work. I'd turn it on in the summer when we were driving through 30C+ weather and I'd never get any cold air out of the system. Could it be this relay that's causing that problem too? I'd assumed that I had a leak in my A/C system and lost all my R12. Or else the compressor had failed.

Can I just pull the KLIMA to see if the clicking is still happening?

Quote:

The ABS issue is likely a bad sensor or a dirty sensor. These can be cleaned and if that doesn't work, you might try replacing them. Not sure if I have ever heard of an ABS computer going bad. Good luck, Jim

Thanks, Jim. Much appreciated. Do these sensors look like the attached thumbnail? These are on autopartsonlinecanada.com as "Brake Pad Sensor". I'm pretty sure we've pulled at least one of these out on my last brake job as it was snapped. The ABS light first came on when I was driving to Vancouver, and I had my brakes changed after the trip, so I don't really know where this could have started.

JimSmith · #8 10-13-2007, 09:22 PM

Go ahead and take the KLIMA relay out and see if things get better.

I doubt the KLIMA relay is the reason the air conditioner is not working, but it is possible. It is more likely some other problem is sending bad info to the KLIMA and it is merely responding. Low freon is a common problem with older cars and if you have not recharged in the last several years, it might be a good idea.

The sensor in the photo is for brake pad wear. That is not an ABS sensor. The ABS sensor is a device that basically counts notches on a toothed wheel.

Good luck, Jim