95 w124 Diesel. Does this sound like OVP? - PeachParts Mercedes-Benz Forum

thatguy · #1 05-09-2012, 01:00 AM

Tonight my car decided to act up out of no where. The ABS light came on, followed shortly by the SRS light, at the same time the blower stopped working and just began making a high-pitched whining sound from near the middle of the dash from what I can tell just poking around; I can still hear the AC compressor engage when I hit the AC button, but it makes no difference as I get no air from the vents. I shut the car down and restarted it, no luck, the lights are still coming on and off (mostly on). I checked all the fuses at the top of the fuse box and none are blown, or even blackened for that matter. It's completely dark now and on this car you have to pull the fuse box coverings off with a screw driver to access relays. Anyway, the tach still works and it starts, but does this sound as though the OVP has died?

Thanks

Jeremy5848 · #2 05-09-2012, 01:44 AM

If the tach works, the OVP relay is OK -- the tach signal runs through the Electronic Diesel System (EDS), which won't get power if the OVP relay dies or its fuse blows. SRS does not use the OVP relay.

This sounds like a low-voltage problem caused by a failed alternator or regulator. Try turning everything off except for the engine, so as to lower the load on the electrical system. Check the battery voltage. You should have between 13 and 14 Volts with the engine running at any speed above idle. If the system voltage doesn't come up with engine RPM you have a charging problem.

Jeremy

thatguy · #3 05-09-2012, 02:01 AM

Jeremy ,

Thanks for the reply. It makes sense now that I think about it, it happened tonight as I was running with the fan blowing, lights on, and radio on. Sounds as if that was too much load. I will check the voltage tomorrow in the daylight, I sourced a new Bosch alternator and it's about $200, ouch. An odd thing here, to me, is the dome light. When I switched the key on with a hot engine, the dome light was flickering like mad when I had the door open, but as soon as I turned the key off the light maintained its normal light pattern. Perhaps it's taking a toll on my battery too.

biopete · #4 05-09-2012, 02:30 AM

glow plugs were sucking all the juice.

chazola · #5 05-09-2012, 04:03 AM

does sound like the symptoms I had when my voltage regulator died, how many miles on your car? You can check/replace the regulator with the alternator in situ, a lot cheaper than replacing the whole alternator if you don't need to...

thatguy · #6 05-09-2012, 12:11 PM

Quote:

Originally Posted by chazola

does sound like the symptoms I had when my voltage regulator died, how many miles on your car? You can check/replace the regulator with the alternator in situ, a lot cheaper than replacing the whole alternator if you don't need to...

It has about 167k on it now, I will be checking it later today when I have some time, I'm hoping that's the case.

Chris W. · #7 05-09-2012, 12:42 PM

Remember that you can buy the regulator separately from the alternator. Very easy R&R, both for the alternator itself and for the regulator.

Rgds,
Chris W.
'95 E300D, 367K

Jeremy5848 · #8 05-09-2012, 05:29 PM

Quote:

Originally Posted by thatguy

Jeremy ,

Thanks for the reply. It makes sense now that I think about it, it happened tonight as I was running with the fan blowing, lights on, and radio on. Sounds as if that was too much load. I will check the voltage tomorrow in the daylight, I sourced a new Bosch alternator and it's about $200, ouch. An odd thing here, to me, is the dome light. When I switched the key on with a hot engine, the dome light was flickering like mad when I had the door open, but as soon as I turned the key off the light maintained its normal light pattern. Perhaps it's taking a toll on my battery too.

The dome light flickering is normal if the door is left open. Agree with the others, it could be the regulator, the brushes (part of the regulator) do wear over time and may be starting to loose contact with the slip rings of the alternator. About $65 and a few minutes to install.

Jeremy

thatguy · #9 05-09-2012, 08:32 PM

Well I put a tester on my battery with the motor running and AC, radio, lights and fog lights running and was getting some weirdo readings. It would wave up and down between 10 and 14 volts, but it was 14 volts at idle and 10 volts at ~1500-1800 RPM. I did look at my fuses and they were basically powdered tin at this point, so I replaced them all with brass/copper and now I suddenly can't get it to recreate the oddity no matter what, it's constant at 14v at idle and up to 3500rpm. I think I should replace the regulator to be safe, I can't have this thing going south on me 100 miles from home.

Thanks again to all that helped me out.

shadetree77 · #10 05-09-2012, 09:16 PM

yeah i would just change out the regulator; i would also source one of those voltage meters that plugs in the cigarette lighter so you can keep an eye on the voltage

Jeremy5848 · #11 05-09-2012, 09:18 PM

It's possible that the whole thing was caused by a flaky fuse. The aluminum fuses are a little less expensive than copper but you pay in other ways. All metals oxidize with age but aluminum oxides are insulators while the various copper compounds are still fairly conductive -- I don't know the numbers, we need a metallurgist's knowledge here. As you have discovered, old aluminum fuses are worthless and new ones aren't much better.

In any case, it's worth putting in a new regulator. Unless the old regulator's brushes are completely worn to nothing, keep the old one as a spare (carry it in the spare tire well with your tools). By installing the new one you'll learn how to do the job in case something ever happens on the road.

Jeremy

thatguy · #12 05-19-2012, 08:13 PM

Well I installed a new alternator with a new regulator and everything seemed to be fine, however, today my initial problems resumed. Driving along for 45mins with the AC running and, out of no where, the SRS and ABS lights come on and my blower stopped working again and emitting that same high pitched sound. Anyone have any clues as to what's posessing my car this time?

Thanks

sixto · #13 05-19-2012, 09:02 PM

Might be time for a new key switch.

Sixto
87 300D^2

thatguy · #14 05-19-2012, 10:29 PM

Quote:

Originally Posted by sixto

Might be time for a new key switch.

Sixto
87 300D^2

Interesting, I've never heard of them doing such a thing. I've been trying to research it, but I haven't had much luck. Have you had this problem before? I find it weird that the warning lights come on and the vents emit that horrendus sound, I'm wondering if I got a bad alternator?

ottomatic · #15 05-19-2012, 10:55 PM

My 95 sat for 5 years before I bought it. I had a host of electrical problems alot of them as you described. I changed fuses to copper and in doing so it eliminated most of them.
My blower or fan finally stopped screeching, (it quit altogether). Today when I put my right signal on,The the wipers come on. ( i feel like an idiot) , The radio still has a mind of its own, (sometimes it turns itself up to full volume) I leave it off now.
However mpg is 36.7 I can live with all its problems with the cost of diesel @ $4.00 per gal.
I've decided I'm not going to sink alot of $ or time into getting the 95 perfect. Just do routine maintaince & fix life threating problems
Every time I do that to an older MB some fool runs into them
( 3X so far: an 82 Td= rear ended & totaled, 83 SDL rear ended & totaled, & 300d t-boned & totaled)
None of the wrecks were my fault. In reality although I collected ins, $ I still lost $ & time overall\

BTW : perhaps you blower motor is shorting out
Also check here 1995 E300D Glow plug issue.. Yes I've searched..