GP relay stuck on - PeachParts Mercedes-Benz Forum

jpauliv · #1 09-19-2013, 01:46 PM

So I was having battery charging issues and used the forum to deduct a number of things wrong in my electrical system. I removed the battery and alternator from the car and took it to autozoo for their free test. Battery less than a year old is good alternator bad. It was a motorola and could not easily find the brushes so I installed a Bosch reman. Thought all was well, 2 days later dead battery. Hooked up the voltmeter while running and saw 12.3v, unplugged the relay and it jumped up to 13.4v. So I know I need a new relay. Guess what it is the three legged relay which runs anywhere from $400(ouch) to $300(ouch). Or I go the manual override route. First I thought I would check salvage yards but haven't had time. I thought I would check the forum members here to see if anybody would have one they are willing to sell.
Also wondering if anyone as gone from the old style to the newer GP relay that uses ambient temperature instead of the coolant sensor. Thanks again

cooljjay · #2 09-19-2013, 02:09 PM

I don't see why you couldn't switch to the newer relay......you may have to look at the later glow plug wiring diagram and then your digram.....switch some pins around in the connectors and plug in the relay....

Zacharias · #3 09-19-2013, 02:14 PM

I went with a manual relay on my Coupe and plan to do the same on my newer 300d, when the current relay dies.

If you want a replacement relay, put a "want to buy" (WTB) posting on the used parts for sale and wanted subforum here. You will get a much better price than what you mention in your posting, probably $50-$75 for used.

connerm · #4 09-19-2013, 02:23 PM

I had the same issue with my 85. I tried two used relays and neither worked properly even though they tested fine. Go new. Someone here made the point that the used ones could easily contain 30 year old electronics. That's a good point.