[W126 Coupe] Suspect OVP relay (old subject-sorry)

[Mike R.]

Have you checked the fuse in the OVP? A blown fuse will create the high idle
(BTDT. 
 
What's the battery voltage with the engine running? When my ABS & Battery
light come on at the same time, my alternator has died and the battery
voltage is too low.
 
Where are you located? I think I have an OVP you could borrow/buy.
 
Later,
Mike Ramay
(702) 494-8056
Las Vegas
 
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Vance Rowley
Sent: Thursday, June 11, 2009 5:56 AM
To: Mercedes Coupes Mailing Lists
Subject: [W126 Coupe] Suspect OVP relay (old subject-sorry)
 
I know this subject has been covered many times, but there doesn't seem to
have ever been any exact diagnoses, and appears to be some confusion on the
subject.
The symptoms are as follows on my 1991 560 SEC (Euro).
 
1. Takes a long time to start, (where it used to start on the first couple
of turns of the engine.)
2. High idle, around 1400-1600 rpm (and sometimes creeps up).
3. ABS and ASR warning lights on all the time.
4. Hesitate slightly when you hit the gas. (more noticable when you rev the
engine in neutral)
 
This I believe is the typical (limp home) mode. I have seen these symptoms
on many forums as well as our archives, but never usually all at the same
time. Also, these symptoms that other people have are usually intermittent,
where mine are permanent. Anyhow, there are quite a few different diagnoses
for these symptoms around on the net, but mostly point towards the
overvoltage protection relay. I have of course checked the fuse in the top
of the relay and is OK, as well as making sure the pins are clean, which of
course they are. Have even tried one tip to disconnect the battery overnight
to try to reset the system. No joy.
 
My main question (before I purchase a new OVP relay) is, can anyone confirm
that this is the problem for sure. Also, I unplugged the relay and started
the car and all the above symptoms remain the same without the relay even
plugged in. This got me thinking. Does this mean if you unplug the OVP relay
on a known good working car, that you will get all the above symptoms? This
would surely confirm the diagnoses and was wondering if anyone has done it.
If so, please let me know, as well as any other tips or hints.
 
Thanks,
 
Vance.
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