Temp Gauge Quit Working

[Dawg]

1994 Chev C1500 4.3L 82,000 miles

The temp gauge recently quit working. When you first turn the key to start the engine, the arm sweeps over to full hot and returns to zero as always. As the engine warms the arm stays put.

I changed out the 2-wire sending unit with no luck. I'm guessing the gauge itself is getting power because of the arm sweep at start up.

All other gauges/indicators work fine.

Any ideas? What am I missing?

Thanks, Dawg

[Dawg]

Must not be a common problem. Anyone?

[Robyn]

Try this

Ground the wire that goes to the sender, the gauge (with key on) should go to HOT

If not then check the dark green wire (sender wire) for an OPEN (broken)

If wire is good all the way to the gauge then the gauge is toast

Wire #35 is a dark green wire and is the feed from the sender all the way to the gauge

Wire # 150 is a black wire and is the ground
Wire # 39 is Pink and Black and is the 12Volt supply

Check the Dark green to make sure its has continuity from the sender to the gauge
Make sure the black wire at the gauge is indeed grounded
Make sure you have 12V at the pink and black wire

If these check out then the issue is the gauge itself.

The electrical service manual says to replace the gauge.

I am still not sure that the gauge can be replaced by itself.

Worst case scenario is you could swap in another gauge cluster from a Bone yard beast.

Let us know, good luck


Missy

[Dawg]

Okay, I didn't really have time to check it out this weekend. Probably won't have any real time until next weekend. I have something a little different than described above.

One-yellow wire and one-black wire leading to the connection at the sending unit. (The sending unit is near the thermostat housing) I am assuming the black is a ground wire. I disconnected the plug from the sending unit and checked continuity at the plug. All seems well.

Can I do something to check the yellow wire alone?

[Robyn]

Temp gauge sender is usually in the LH head near the LH front corner and has one wire going to it.

The temp sensor in the water X over is for the ECM to monitor the system temp and not the gauge.

Check the LH head for the gauge sender.

Missy

[Dawg]

I'm sorry it has taken so long to get back to you. I have been tied up with managing the 9/10 year old boys All-Star baseball team. We are out, but be had fun.

I looked the truck over tonight. On the driver side I have 2 sending units both near the same spot at the rear of the engine. One looks to be in the head, the other looks to be in the block.

Top one appearing to be in the head- Larger with silver body with one blue wire going to it.

Lower one appearing to be in the block- More of a standard style sending unit with one green wire going to it.

I think we are onto something here. Can you help me determine which one is correct?

I now know the original sending unit I was looking at was the one the ECM monitors for system temp and not the gauge.

Thanks again.

[Robyn]

The one in the head should be the temp gauge sender.

I have never seen a gauge sender in the block on a GM rig ???

Where on the block is the other sender ???

Missy

[Dawg]

Both of these are very near #5 cylinder. The larger of the two units being above the smaller one.

[Robyn]

I am not familiar with the V6 engines but they can't be all that different.

My 92 GM wiring book shows the Gren wire to the gauge sender.

The only single blue wire I found connects to the KNOCK SENSOR.

Replace the unit with the green wire and you should be good to go.


Missy