photocliff

I am looking for ideas on what I should do.

On my 69 302 the coil wire and the temprature sensor wire seem to blink on and off. They don't stay constant. To get the engine to start I have to jump a wire from the "I" on the selenoid and when it's running the temp gage is all the way over in the hot position. I don't want to leave the jumper wire on because of possible damage.
When I put a circut tester on the wire the tester light blinks on and off. Both at the same speed. I know I could have a bad ignition resistor wire but what would cause the temp sensor wire to blink too? Is the temp a resistor wire too? The oil pressure wire seems to work just fine. (The three wires are coupled in the same connector coming out from the firewall).

67t5ponycoupe

Sound like the harness from the firewall to the engine has issues. It has your coil, temp and oil pressure. Unplug the harness at the fire wall and check to see if you have voltage on the coil connection. If not you may have a bad resistor wire or wiring issues under the dash. The coil wire may be shorting on the temp wire and causing the temp gage to peg.

vescotech

The temp sensor wire should blink when testing it with a test light. This is caused by the constant voltage regulator on the instrument cluster. Does you car have an oil pressure gauge or an idiot light? If it has a gauge the oil pressure sending unit wire should blink as well.I know you said it was working but is there any chance you may have the coil wire pluged onto the oil sending unit and both wires you are checking are for the gauges? If not the coil resistor wire might be broken and shorted to the temp wire. Pull off the I wire at the solenoid and check to see if its blinking too. It connects to the ignition wire at the coil. If the ignition wire is blinking it should be too.

Stepman

It sounds like your wires are mixed up. The temp and oil wires should be a pulsing power, the coil should be constant. I'd check to make sure the wires stay the same thru the plug.Then, check them to see what kind of power is on each one. Finally, turn the key on and ground the one you think is for the temp, then the oil, and see if the gauges peg. Also, the coil should be the thicker of the 3.

Starfury

I agree with Stepman, sounds like the wires are hooked up incorrectly. That said, the coil wire should be pulsing with the engine running. Every time the coil charges, voltage is going to drop at the coil + terminal.

photocliff

I did unplug the, three wire, harness and got the same results that I got at the wire ends. The harness came from Mustang Depot and all three wires are different lenths. I assumed the longest one shoud go to the oil pressure unit since it's the furthest reach for a connection.
If the temp and pressure wires are supposed to pulsate then that means I have the coil wire connected to the oil unit because thats the ony one not pulsing.
After reading these responsess I also figure that if i dissconect the "I" wire at the seleniod and then test all three I will find the right wire for the coil

Thanks for helping me expand my problem solving skills in the area.
Thanks, I will get to it this coming weekend after it warms up a little outside

jlg2002

FYI, IAW the Mitchell manuals I have, the coil wire is Red with a Green stripe, the water temp is Red with a White stripe and the oil press is White with a Red stripe.

MIL1ION

This below is normal for a sending unit signal wire

Temp,Oil & Fuel

photocliff

BINGO! Thanks jlg2002 That is what I needed. Now my oil gage seems to not work. I wonder if I ruined it having the wires crossed. I know I have oil pressure but the gage didn't move. Thats what makes it fun to work on. Something new to figure out!