Parts Catalog Accessories Catalog Tech Info Tech Forums
  Search our site:    
 Cart  | Project List | Order Status | Help    

Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

LinkBack Thread Tools Display Modes
Old 10-18-2001, 12:09 PM
Registered User
Join Date: Aug 2001
Location: Santa Maria, CA
Posts: 49
Overvoltage Protection Relay Failure Modes

There has been a lot of talk regarding the infamous OVP and how it contributes to or causes any number of failures in our Mercedes cars.

My question to all of you smart Mercedes mechanics (MBDoc, Benzmatic, etc.) is:

What are the failure modes within this relay that cause these problems?

The unit has a zener diode and a relay as its main constituents. Do the contacts burn or get dirty? Does the zener diode short out or open up? Does the relay functionally die? Does the zener threshold voltage change, perhaps as a function of driving conditions??

I pulled mine a few days ago and checked the relay operation, the contact resistance and the diode function (except for the threshold voltage). Everything checked out.

If all of these tests are ok, can I assume that the unit is fully functional, and not a contributor to my warm start problem? Or is there some other failure mode (perhaps intermittant) that is not easily checked?

If we had a set of tests we could apply to verify OVP operation we could all save wasted money troubleshooting by replacement.
The OVP tests in the manual only check for catastrophic faults.

Thanks guys

Tom Elerding
Reply With Quote
Old 10-19-2001, 12:17 AM
Senior Member
Join Date: May 2001
Posts: 104
the ones that I have seen fail get solder cracks from heat - cold cycles. Look with magnifying glass and resolder any that are suspect. Maybe if somebody else has seen internal component failure, Iwould be interested in knowing.
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Over-Voltage Protection Relay - Failure Mode pberku Tech Help 4 12-28-2004 12:57 AM
1987 Mercedes 190e 2.3 and Overvoltage Protection Relay Eidetic57 Tech Help 3 12-13-2004 12:07 PM
overvoltage protection relay 560SL jcciem Tech Help 1 03-31-2003 12:42 PM
OVP - Overvoltage Protection Relay, right one? LAFetner Tech Help 4 10-11-2001 02:03 AM
overvoltage protection relay LAFetner Tech Help 3 07-31-2001 07:58 PM

All times are GMT -4. The time now is 09:21 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page