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Old 02-15-2003, 03:25 PM
Registered User
Join Date: Apr 2002
Location: boston ,Ma
Posts: 153
ovp ?

I changed the ovp about 6 months ago due to an eractic idle now my abs liight comes on when the car is idling with the heat and radio on.When i step on the brakes the abs comes on also , the car would actually die unless I turn off the headlight,drive with just city lights on and also shut off the heat.

What should i check b4 i blame the ovp again.If someone has a spare ovp relay i would buy just to have as a back up .Dont want to spend another $ the way i did check the fuses on the ovp everything seems fine. thanks guys

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Old 02-15-2003, 04:56 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
There must be a thousand posts on this.

The OVP is just a power supply relay. It makes NO decisions except that it filters voltage spikes and prevents an overvoltage to the control units. Most of the time it is not intermittant. It can be tested by seeing if the control units have power. The easiest way to do that is to test the output at pin#3. If any output good or bad occurs the system is working and the OVP has done its job.

The one intermittant I have seen is a voltage drop through the unit caused usually by a high resistance connection where the output terminal attached to the printed circuit. Measuring the voltage at the output is the most definative test but is a lot harder to get at.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 02-15-2003, 05:31 PM
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Join Date: Apr 2002
Location: Surrey, Uk
Posts: 254
The clue here is the heater and headlamps causing the car to die. Check your alternator, if it can't cope with all those accessories switched on (it should be able to) the system voltage will drop and then,

1. The Abs computer will shut down and bring up the warning light

2. The ignition will become weak and the engine die.

I don't think this one is anything to do with the OVP relay as this has nothing to do with lighting or heater circuitry.
Mick J
'08 Chrysler 300CRD (MB OM 642 engine)
'95 E220 estate
'89 230TE (R.I.P.)
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Old 02-15-2003, 05:59 PM
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Join Date: Apr 2002
Location: boston ,Ma
Posts: 153
I thought it was my alternator also because when the abs light comes on with the headlight and heater on I would shut everything off and try to start the car it would start but it seems that the battery was dying very weak
I did a simple alternator test by unplugging the negative cable while the car is running to see if it would die it didn't .So my guess is the alternator might still be good .If the alternator was bad would nt the battery light come on ?
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Old 02-15-2003, 08:28 PM
Posts: n/a

Educated guess might the regulator brushes.

If I run the heater, lights, seat warmers and the rear defroster all at once, the ABS and SRS warning lights come on. The manual says this may happen. The bun warmers take a lot power.

Suggest you check the brushes. They go more often than an alternator.

The battery might be suspect as well.

Finally, check the ground connections -- especially by the battery. I found a loose one that caused the lights to come on more often than they do now.

Good luck,

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Old 02-16-2003, 10:13 AM
J.HIDALGO's Avatar
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Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
I also suspect the voltage regulator!

The brushes wear out, you can check them in 5 minutes. They are behind the alternator held with two screws. Your battery may be going south too. Check the voltage...
'86 300E
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Old 02-16-2003, 11:15 AM
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Join Date: Apr 2002
Location: boston ,Ma
Posts: 153
thanks a lot guys
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Old 02-16-2003, 08:45 PM
ebennz's Avatar
Join Date: Nov 2000
Location: Hurricane, West Virginia
Posts: 878

if it is your alternator, you might be able to upgrade to one with more amps.

gsxr did this recently, check his posts.


*92 400e 124.034, SOLD

*92 300e 124.030, SOLD
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