87 300D NO tachometer-NO A/C-ABS problems///Good fuse in OVP relay///Bad relay????
 

I have a 1987 300D and my Tach doesn't work, my A/C doesn't work and My ABS pulsates some times at low speed when I apply the brakes,and the ABS light is on.
Thanks to this forum I found out to check my OVP fuse and It checked good with no corrosion on the contacts, Do you think the relay could be bad? Was it a common problem, How do you check them?
Any advise would greatly help
Thanks to all in advance.

David Lee , Portland Oregon
87 300D
87 190E 2.3
84 230E Euro

A common problem, the solder on the circuit board in the OVP relay cracks on/around the pins of the relay's frame.
Cut the can's corners and pull the assembly out of its case to examine and repair any broken joints, don't use too much solder, a little silicone sealant on the cans lip will hold it together after the repair.

Once again this forum has helped me, plus Ive learned something new
I will do what you suggest and hopefully find the broken link.
thanks again for the input.

David Lee Portland Oregon

87 300D
87 190E 2.3
84 230E Euro

I took my OVP relay out today, and tried to disassemble it with out damaging it, I pulled back the metal where they pinched it the bottom and could not seem to pry it out of the case. Im Stopping now. I dont want to damage the relay as to where It can't be used again.
If any one has a tip on how to take this relay apart for inspection
The knowledge would be greatly appreciated.

Thanks to anyone that might be able to help.

David Lee Portland Or. USA
87 300D
87 190E 2.3
84 230E Euro

Might want to check the CPS if your year had one. Is usually on top of the trans bell housing and can be seen from the top.

Here's a thread I started a while back while having some of the same issues you are having:

http://www.peachparts.com/shopforum/diesel-discussion/305766-ovp-woes-dissection-pics.html

Sorry the pictures weren't better, but I worked with what I had.

I checked under the hood with a flashlight and could not see anything connected to the bell housing, but, the 6 cyl engine sits very close the the fire wall and it is hard to see.
Maybe some one out there knows if my car has a CPS and if so, Where it is.
If i dont get any response on it Ill start a thread.

Pics where great, Thanks, I dont think I will attempt that surgical procedure until I have an other working one handy, but I will use those pics later on.

One more question, When I unplugged my OVP on my 87 and started the car, the car ran like s*#t. so I reinstalled it and then it ran fine again. Does this mean , my Tach, A/C, and ABS issues are some other problem?
What else to look for? Haven't been able to find out yet weather or not I have a CPS and What symptoms it causes when one goes faulty.

Thanks again for all the thoughts and advise so far.
Anyone's additional thoughts will still be greatly appreciated.

David Lee Portland Or. USA
87 300D
87 190E 2.3
84 230E Euro

I should have paid closer to your original posting. If your brakes are pulsing, the ABS is powered (indicating the OVP is working for that circuit) and more likely you have a bad sensor or gunked up chopper on one of the wheels. NOTE: When I have a bad sensor, the brakes pulse coming to a stop when the ABS light is OFF. When the ABS light is ON, the brakes NEVER PULSE.
The fact that your idle went to crap when you pulled the relay is also an indicator that the relay coil/contacts are functioning properly. I'm thinking you may have an issue with one pin (corner #87) that I found at least controls the tach. As wireman said in the second post, it may just be a bad solder joint at the pin.

I think I paid less than $20 for a good used OVP on ebay. Even if it doesn't solve THIS problem, having a spare that you can just throw in the glovebox etc. for the future is a good investment IMHO.

Gonna order an other OVP to try out this week. then i'll I dissect mine.
Also gonna get it on a lift and inspect the wheel sensors.
Thanks again and I will update this thread after I know more

You guys are great!!!!!!!!!!

David Lee Portland Or. USA

87 300D
87 190E 2.3
84 230E Euro

The front wheel sensors can collect a significant lump of debris on their sensing face, the hub has cut grooves on its periphery to form the phonic wheel/chopper which can rust up or corrode away. You don't need a lift to access them just take off a wheel and remove the single sensor fixing bolt to allow the sensor to be pulled and the teeth inspected through the hole.
The rear sensor (I'm making a guess that you have the 3 channel system) is mounted in the diff, it is not prone to rusting since its oil immersed but its cable can be damaged, look carefully at its wires as they pass into the body of the sensor and body of the car.
Be wary of the sealing ring if you take it out of the diff, it is a non stock size and in the UK is MB only. The sensor wires go the a terminal block under the rear seat, LHS next to the locking pump.

You seem a shade wary of hacking into the OVP, here's how I get in them:-
To open the can use a craft knife to trim off the bottom corners of the canister, about 1/4"-3/8" will do it, the side crimping can then splay out as you withdraw the moulded base from the can. A file could also be used to remove the corners.

To re-seal it I used silicone sealant, the sides will spring firmly onto the base moulding and if you've not cut too high up the corners will seal perfectly well with just a smear on the base's sides. The transparent non acid silicone sold for aquarium building works well.

I have found several defective relays in the past, some will begin to function again if they receive a sharp tap, as sure sign of intermittent internal connections.