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

[Vance Rowley]

Hi Mike,

  Yes, the fuse is OK, and the voltage with the engine running seems OK at 13.9v. Also, thanks very much for the offer of the OVP, but unfortunately, I am located in the UK (although I do sometimes visit Vegas each year in November during the Global Gaming Expo), sadly I don't think I will be going this year, and of course I am hoping to get the problem sorted before then anyway. Thanks again for the offer, all help is always appreciated. I must remember to look you up next time I visit. 
One more thing is, I have noticed there are a few variations of the OVP (different part no's, some with one fuse, some with two), but from what I can tell from the little circuit diagram on the side of my relay (201 540 32 45) and comparing it with the photos of others I have looked up on the net, it doesn't look as though it makes any difference as long as it will fit into the socket. In fact when I looked up my part number on a UK based parts supplier, it returned part no 201 540 37 45, one with two fuses and a red top with an additional circuit which would be redundant if plugged into my socket. From what I can tell, this should be fine as the first circuit looks the same. Am I correct about this?

Cheers,
Vance
  ----- Original Message ----- 
  From: Mike R. 
  To: 'Vance Rowley' ; 'Mercedes Coupes Mailing Lists' 
  Sent: Thursday, June 11, 2009 2:44 PM
  Subject: RE: [W126 Coupe] Suspect OVP relay (old subject-sorry)


  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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