Hi i'm new on this forum. I just recieved my OVP relay today and tried it on right away. The one that came through the mail has 2 fuses on top. The OEM i had only has 1 fuse with less studs that fits at the base of the unit.I started the car (same idle, stalling) and when i tried to shut it off, the key went all the way out but the engine keeps runnning (no key on idle). Which btw, happens when i put a new fuse on the oem relay which has a broken fuse. I have no idea what happened! Any comments/suggestions/thoughts will be greatly appreciated.

 

I forgot to mention my car is a 1989 Mercedes Benz 300e.

 

No change in my response to your query on another thread.
The only thing that will keep the engine running with the ignition switch in the off position are the switch contacts or wiring to the switch.
The OVP cannot keep an engine running as it has naught to do with the primary and secondary ignition circuit.
The ignition switch contacts are open in the off position which prevents any power going to and energizing the coil or anything else.
In essence it is a "master switch" for all the systems that the battery feeds.
Once turned from the off position it provides power to various relays that activate the systems in the vehicle.
With the coil de-energized there is no spark and no ability to have combustion, hence no running.
You may also check the ignition switch wiring to see if there is a cross over from any 12VDC+ that would create a jumper and negate the switch itself.

 

Actually the same thing happened to me I had to pull the replacement ovp out in order to turn the car off I dont know why this happened, as 300Edd said The one that came through the mail has 2 fuses on top. The OEM i had only has 1 fuse. i will attempt to replace my ovp with the same exact relay instead.

 

For the W124 series cars there were essentially four different types of OVP used - a 5 pin, single 10 amp fuse version used early on (201 540 08 45), a 7 pin single 10 amp fuse version (201 540 32 45) used in production until the M104 HFI engine, a 9 pin dual 10 amp fuse version (201 540 37 45) that superseded the 7 pin version, and a 9 pin single 15 amp fuse version (000 540 67 45) used on said M104 cars. The 9 pin dual 10 amp fuse version is backwards compatible for 7 pin 10 amp single fuse applications, so it does not surprise me that this is the version you received, especially since the 9 pin is the updated part (note that even though the 9 pin relay has two fuses in it, only one is actually used in the W124 application). No other versions are interchangeable with each other.

As for your problems with the engine continuing to run after the key is switched off, if the problem only shows up when a good OVP and fuse is in place, but the problem goes away when the OVP or fuse is removed, the problem is almost certainly that there is a "connection" between the OVP controlled ECU loads and the hot in run/start side of the ignition switch.

Sometimes a D.P.O. will "jumper" the ignition switched circuits to the ECU circuit to "fix" lack of power to ECU functions like the IAC, etc. when an OVP has failed. This works fine until the fuse/OVP is replaced at which point the cross feed will cause the OVP to "latch" on and back feed the hot/run circuits and keep the engine running. The engine won't stop until the OVP or its fuse is removed. It is also possible that a defective CISe unit or MAS controller could be causing the back feed as well, but I have not read about that happening.

Diagnostic test: With the OVP and fuse in place start the engine and turn off the key, assuming the engine keeps running, remove Fuse 6. If the engine stops, the cross feed is in the Fuse 5 or 7 circuits. If the engine keeps running, the cross feed is in the Fuse 6 circuit or potentially the MAS controller.

Good luck,

- FD

 

Thank you for your reply

 

Dwalker, sorry for the late reply. Yes i did find a way to end that problem. It was a used 7 pin with the same part number i bought from Ebay. Seems that when i have a new fuse on my old OVP, it just wont stop running when you turn it off. Same as with the new OVP relay that i bought from the dealers (what a waste of money). DO NOT change the ignition switch. Now i'm just waiting for my used ECU from the mail and see if it fixes the shutting off on traffic/stop lights. Hope this'll help.

 

I drive a 1994 SA built W124 with the M111.960 powertrain and I have had loads of hiccups.

Car had rough idle and running rich when I purchased.
Wiring Harness replaced by MBSA under warranty somehow before I purchased but they did not replace the wiring to the ETA.
I rewired the ETA and plugged in. Car ran horribly, hardly idling.

I replaced the MAF, fine for about 200km. Car back to running poorly.

Next I started fiddling with the OVP, got it running smoothly again. Next morning running poorly again.



I went ahead and asked a friend to bring me an OVP, at this time I was not aware there are different types.

As soon as I plugged in the OVP, the powertrain primed for startup. Climbed in behind the steering and dash lights all on, ready to start.

Started, and ran perfectly, would not switch off again.

The supplied OVP was a 7pin, manufactured in 1988. Single top fuse(10a).

The original is a Single Top Fuse (15a) 9 pin.

Is there any workaround to make the older 7pin work with my car?

The dealers are charging crazy money for the part. (ZAR 1874.00)