Temp Gauge Problem?

Hi there all! First I would like to say nice site you have here. I didn't know it was around till this morning.

Ok here is my problem.

I have a 1991 Blazer S10 model with a 4.3L. The motor I have in there is out of a 88 Astro Van.

My temp gauge on the dash doesn't work. I have changed the whole cluster with 4 others and still won't work. I have tested my coolant temperature sensor with a ohm reader and it works fine. Now somewhere I read that I should have a sender. I have a loose wire that is green and I suspect that is my sender wire. But the place where I would have the sender is plugged and I am certainly missing it. I am unable to get the plug out due to rust and corrosion. Also it is a square inside the plug, not sure what to use to take it out.

So because of that my idle is really high because the CPU reads the gauge as under 40 degrees and thinks it's warming it up, right???

Well my gas milage is outrageous, and it's hard on the u joint shifting it when the idle is to high.

Is there a way I can wire up the wire (green sender wire)to something else to fool the CPU???

Or do I have to find away to take out that plug on passenger side above manifold and put in sender.

I thank all who try to help me on this.

Welcome to AF.
Your engine uses 2-3 temt sensors.
One for dash gauge and one for engine tempt and some have a air tempt sensor.
The engine and air tempt sensors use two wire sensors.
Work on them first.
MT

On your engine I do not see a aAIR tempt sensor.
The computer tempt sensor should be on top front of engine near or in thermostat housing.
Also check all of the ground wire at thermostat housing.
It uses two wires yellow and black wire.
Black ground and yellow to computer.
Find and check that sensor and check wiring plug.
They have a lot of wiring problems at sensor.
You can buy a new sensor with a new wiring plug in.

If the computer is reading out -40 on engine tempt the sensor may be unpluged or bad or wiring bad.

The tempt sensor in the head is for the dash gauge and does not affect the engine running or computer.
If you can not get the pipe plug out of the head look on intake and thermostat and on engine for anothe plug to water to engine cooling.
But works the dash gauge.
Also on dash gauge check fuses.
MT

thanks for the replys. I just want to make sure that I understand this correctly.

The black and yellow wire that go to the coolant temp sensor go to the computer and don't need the sender(passenger side above manifold) to get reading on the dash? Right.
So if I don't get a reading on the gauge, I must have a boken wire somewhere. Or even my sensor is shot. I did do a OHM reading on the sensor and I have the right resistance when I made it hot and cold. But I will pick up another sensor anyways to make sure.

But if it reads -40, that's what makes my idle high right?

Heres another one, My oil pressure gauge doesn't work either, LOL.

any ideas?

Could there be any other issues I can check? If it reads

Yes they are two seperate sensors.
The one in the cylinder head works the dash gauge.

The one on top front of engine with the black and yellow wires feed to the engine computer.

If the computer is reading -40.
The sensor is not working or wiring from it to computewr is bad or the computer itself is bad.

If the sensor has good ohm readings check the wiring from it to the computer.
Check the ohm readings on the black and yellow wire where they plug into computer.

If no ohm reading there the wiring or plug in is bad.

If good ohm reading there and the computer reads -40 the computer is bad.

If computer is reading -40 it is running in a full rich or a real cold mode.
And may be on fast idel.

Fix the computer tempt sensor first.
MT

ok then that my problem, I have only the one sensor by the thermostat and none by the cylinder head. I have a loose green wire that should connect to a sensor.

Now since I have hard time taking out that plug that the sensor should go into, can I just wire up that green loose wire to the yellow to get a dash gauge reading?

If not, any Ideas on how to take out the plug, It seems to be a square type of wrench needed, I tryed to put a 3/8's ratchet to it, but it's a little to big.

No way that will work.
May even blow coputer.
They are two seperate and different sensors and each one will have to be wired right.
Is the computer tempt sensor working right or have you fixed it.
If you can not get on plug out of the head for dash gauge sensor try the other plug or go over to the head on other side.
or look for a plug to water jacket on other parts of engine.