OVP Relay - ABS light - Hard starting
 

After reading Steve Brotherton's article in DIY I have newfound hope in diagnosing a couple of continuing problems with my '91 420SEL. One thing in particular that I want to check is the OVP Relay....if I could only find it.

A year ago I sent my 420 into the shop for some major overhaul work. A timing chain guide broke, mucking up the chain and a couple of valves. I redid a bunch of stuff as long as I had it apart.

Now, before the timing chain broke the car was running great, started right up and ran smooth. When I took it back from the mechanic I noticed 2 things - first, the ABS light was on (it was NOT on prior to this.) Second, it did not just start right up like it had. It started a bit rough and it has been getting rougher ever since. When I complained to the mechanic about this, he said he thought the rough starting was a problem with the fuel injectors. I was skeptical so I took the car as-is and have been dealing with it ever since. When I drove away, I also noticed that the Cruise Control did not work anymore. I called him back and he said I'd need a new cruise control actuator and that was also why the ABS did not work.

I refuse to throw parts at a problem when I'm not sure of its origin, especially after I had just laid out over $2,000 for the rebuild. When I ran across Steve's article here last night a few lights went on. OVP relay - rough starting - ABS light. Could be.

So...if anybody knows where this little rascal can be found, I'd surely appreciate it.

Here's a photo of the OVP(over voltage protection relay):

http://catalog.eautopartscatalog.com/smittys/sa/wizard.jsp?partner=smittys&clientid=sasponline.com&baseurl=http://www.sasponline.com/&cookieid=17R0ZW5V7&year=1991&make=MB&model=420-SEL-001&category=P&part=Overload+Relay

You can click on the photo to expand it.

It's at the back of the engine , about in the middle of the "first" firewall.