just a few wiring questions

[65truckowner]

I am almost done with my 66 frame off. I have a couple of problems I cants seem to figure out. One is my oil light stays on when the engine is running. The engine has 30 psi at a warm idle so I no it has enough pressure. It is a 350 engine. The wire that plugs into the sender is hot with the key on and when the engine is running but once plugged in it is not hot anymore... The other problem is my temp lights the green and red do not work at all. I have a new sender for them as well. Any ideas would really help.

[shp4man]

Wrong senders?

[jtrichard]

Pull the wire off the oil sender if light goes out = wrong or bad sender ......if still on = wiring problem ..... take the wires off temp sender with another wire ground out each wire (one at a time) and see if lights come on if not check bulbs if good then no power to bulbs OR bad wire/s to sender

[ray_mcavoy]

Yes, as shp4man said, you might have the wrong sending units. There are different ones for warning lights vs. gauges.

The circuits for the "OIL" as well as the "HOT" and "COLD" temp lights all share the same basic design. Switched power (from the ignition switch) is routed to one side of the bulb. The other side of the bulb is connected to the sending unit. And the body of the sending unit is grounded through it's threads that screw into the engine. In the case of warning lights, the "sending units" are basically just on/off switches that open/close at a certain pressure or temperature. When closed, they complete the circuit to ground which turns on the corresponding dash warning light.

With this circuit configuration, it is normal for you to be measuring voltage on the sending unit wires with the key on (or engine running) and the wire unplugged from the unit. The fact that the wire is not hot anymore (and the light comes on) when you plug the wire back in indicates that the contacts in the sending unit (switch) are closed. Since your engine has more than enough pressure to open the oil switch, it sounds like you are dealing with either a stuck/defective or incorrect oil sending unit/switch.

As for the hot & cold temp lights, try temporarily grounding the sending unit wires. Grounding them should turn on the lights. If it does, the issue is the sending unit/switch. If not, check for loose connections in the wiring, bad bulbs, etc.

[65truckowner]

Thanks guys. I have looked at the oil sending units in my parts books and I must have the wrong one It is the larger one instead of the small one that looks kind of like a spark plug shape. I will ground the temp wires and see what happens.

[65truckowner]

Ok I fixed the oil light. It was the wrong sender. I have not checked the temp lights yet. I drove it to a cruise in tonight and when I got home I could smell burnt rubber real strong. I checked all the tires and nothing was rubbing. I also checked the belt on the engine and it was fine. Any ideas??