OVP relay
 

Like everybody else I have had problems with this cunning device. The biggest problem is the circuit board which has holes which are far too big for the pins and components soldered in them. I believe the vibrations of the relay stresses the soldered joints resulting in a crack which is very difficult to see even with a magnifying glass. Resolder all the joints with plenty of solder first before throwing it away.

86560SEL, The OVP isn't model-specific, but there have been several versions of it (5-pole, 7-pole, 9-pole) and the earlier ones and the later ones (approx. 1988+) have different part numbers. Early 80s 126 V8s (thru MY '87) have OVPs that should work; not sure that W116 even had an OVP. S-class experts will know for sure and can correct me on that. Why do you think that you need an OVP?

Somebody said in an earlier thread that the OVP was there to protect the ECU and ABS relay if the car was jump started with reversed polarity He therefore suggested that the OVP could be removed and the socket jumpered, but he didn't say how to go about that. Anybody have any ideas on how to do it.

True, the OVP supplies power to both the CIS-E and ABS control units, and protects them from excessively high voltage. Bypassing the OVP by connecting a jumper wire between the OVP connecter sockets would allow the car to run, but how smart is it to put $4,200 worth of control units at risk because you don't want to spend $80 for an OVP?

Might also be to protect against "load dump" when the field collapses in the alternator and other devices after being shut off, can cause a high-voltage reverse-polarity pulse known to us who design automotive electronics as "load dump".

M.B. realised that this was a troublesome item when the cars were in production. They tweaked the electronic specifications to try and get them dependable and reliable.
There advise is to get the latest model of OVP available. As the previous poster has mentioned - why risk expensive components for a comparatively cheap item.

Rubber products and electronics decay over the years whether used or not. In the electronics industry we know there is gradual deterioration of electronic components due to slight alteration of chemical properties of materials, static and electrical or RF interference. These problems manifest themselves ranging from intermittent faults and operation to ultimate breakdown.

Thanks... well my car is actually a 6-cylinder (300SEL). Now I wonder if the V8 / I6 relay is compatible?

The reason I think I may need one is that my car has very recently and suddenly started to stall out when I come to a stop. It always starts back up and goes fine and runs smooth. I am also getting 21 mpg in town.

On other threads however I have also been told it could be a vacuum hose or a bad fuel pump. I am going to try to take it to a Mercedes indy shop next week to have it checked out.

Parts page is finally up and I think this is the new one...
http://catalog.peachparts.com/ShopByVehicle.epc?q=1988-MERCEDES--BENZ-300sel&yearid=1988%40%401988&makeid=63%40%40MERCEDES%2DBENZ%40%4063%40%40MERCEDES%2DBENZ%40%40X&mode lid=6220%3AMBC%7C1515%3AED%7C10000012%40%40300SEL&mode=SS&yearid=1988%40%401988&makeid=63%40%40MERCE DES%2DBENZ%40%4063%40%40MERCEDES%2DBENZ%40%40X&modelid=6220%3AMBC%7C1515%3AED%7C10000012%40%40300SEL

Thanks again.