1984 245 DL automatic 4cyl. non-turbo: My oil light came on steady after lots of flickering over a 50-100 mile time frame. The oil quantity is good, I changed the sending unit after I put a gauge in the sending unit hole and got 45 PSI cold and abt 38 PSI r warmed up. The oil light is still on constantly. Based on the aforementioned results I'd say I have a ground somewhere in the wire from the sending unit to the warning light. The wire leaves the sending unit and looks good for the first 8-10 inches when it disappears into a wrapped wire bundle. I would think the easiest fix would be a new wire from the sending unit and splice it into the original wire somewhere before the firewall?? Can anyone tell me where I might find the oil warning light wire just before it goes through the firewall? or Could someone give me a viable plan to fix the this problem, short of relinquishing my problem to a professional? Thanks

/// Disconnect the wire from the new sending switch first. You can break the new oil pressure failure switch unit by using too much pressure with the wrench. There is a diaphraghm inside that seals to the outer case. If you bend that case on installation the new one can be broken.

The thread on these switches are a special case of the 1/8 inch pipe thread. The tube is cone shaped so that there is a stop point on installation. No sealer or teflon tape is needed as long as the switch is threaded into the cast iron block. Be gentle with the wrench.

There is a grey 8 pin plastic conector about center of firewall where the engine harness conects to the car harness. Oil wire black, temp sensor wire yellow. Disconect the conector and check the engine side to see if wire is grounded. If so, you have found the problem.

You might want to try disconnecting the wiring harness to the back of the insturments and disconnect the lead to the oil pressure sensor. Then take a multi-meter and test the resistance of the wire, relative to the ground. Hook one wire of the meter to the wire and one to the engine. If you get low resistance or 0 ohms you probably have a short. I know the insulation has been know to deteriorate on some model years.

I beleive this will work. It has been a while since I have looked at the wiring diagram of a 240. I am reanoably certain that this wire only goes to the instument panel and oil pressure sensor. I have been wrong in the past, when firing off from the tip of my brain!

Hope this helps.