Hello I am working on my 1985 Corvette.ni am trying to locate the wire that goes to the I/P Coolant Temperature Sensor.
According to the FSM it is in the alternator wiring harness. In the alternator wiring harness I found the wires to the alternator and one olive green wire. I think that the olve green wire goes to the oil temperature sensor.
My son in law sent me photos of my 1989. The wire to the coolant sensor is green with a white stripe. The oil temperature sensor wire is olive, on the 1989.
Can I get some help on this please. I control f the FSM and it only gave me the picture of the connector on the motor but nothing indicating it's color.

Thank you

 

COOLANT TEMP - GREEN

OIL TEMP - GREEN/WHITE STRIPE

I believe in some of the FSM there's a .8 BLUE mentioned but I understand that's maybe erroneous.

See the cluster wiring diagram - that should confirm

 

Thank you.

So what I am reading from your post is that both of these wires go directly to the cluster. So if all else fails I can run a wire from the cluster to the sensors. Correct?

Thanks again

 

I'm sure not an expert on the '85, but I thought the CTS for the gauge in the '85 is on the RH side of the engine, between plugs 6 & 8. If that's true, It doesn't make sense that the wire for that sensor would be in the alternator harness. I suspect that CTS wire would be green where it goes to pin 2C in conn. C100 on the firewall. The wire at the CTS may be blue, but changes to a green wire at another connector. (Maybe? If I'm off base, I'll retract this post.)

 

first of all no one that offers help is off base. The 85 Corvette has a CTS in the front of the motor. It talks to the ECM and controls fuel flow.
There is an I/P Coolant Temperature sensor in the left head. That I now believe goes directly to the instrument cluster.
On the passenger side is the fan switch that turns on the coolant fans.

So today I was working on the car. replacing the tachometer filter and realized that the previous owner had connected the tach filter wire to a green wire that lives in the alternator harness. I think it is the oil temperature wire. It was missing most of the insulation. I think it came in contact with the exhaust.

I did find a brown wire without a home. Connected the Tach filter to it and now I have a working tach.

But, I also have anew problem.
The body of the tach filter is hot. If I put my test light on the filter and negative terminal. The test light lights

Does anybody have any idea what would make the body of the tach filter hot.

 

I think I found the oil temp wire. I was connecting the tach filter and realized that the tach filter was connected to a green wire that was in the alternator harness. I had a brown wire without a home.

I connected the tach filter to the brown wire and the tach port on the distributor. The tach works but the tach filter body is hot. If I put a test lamp on the body of the tach filter the light lights. Why does it have voltage on the body of the filter.

Thank you

 

It sounds like you found your sensor! The one on my 1988 C4 is between cylinders 1 and 3 (Left side of engine from drivers seat) and has the green wire going to it. It is a single wire connector as that is what the dashboard gauge reads from. The ECM gets it signal for temperature from up in front of the engine under the throttle body and that sensor should have two wires going to it. The second wire is a reference Voltage used by the ECM for more accuracy. The reference voltage is 5 Vdc on one of the two wires from the ECM Coolant temperature sensor.

I have had the darnedest time getting a new end for the wire that goes between cylinders 1 and 3. It is a single wire plug that locks on to the sensor body to help maintain a good solid connection.

Sorry, I have never messed with a "Tach Filter", I know where it is and what it is supposed to do but have never touched one yet as mine still works fine.

One thought, while you are near them you might want to verify the operation of the coolant temperature sensors while you are there. They produce a resistance that correlates to a specific temperature. They are easy to test with a Volt Ohm meter and the chart from the Service Manual.

Good Luck with your Corvette and lets get our Corvettes back on the road where they belong!

 

This is a great response. I thought the CTS in the front of the motor was tested by voltage. 5 volts cold and 1.5 at operating temp.
Rockauto cells the coolant temperature sensor connector for the I/p sensor. Have a great day and thank you