Temperature Gauge Pegs Out

[sonicbluezx3]

Okay I have a question for you guys....

First of all, let me explain a little bit. My truck (1986 K10 Shortbed) originally came with a 4.3L V6 engine. The guy I bought the truck from swapped in a 6.2L diesel engine. He used the original wiring (set up for the gas engine) and everything worked fine. I just did a total overhaul of the body, and in doing so, I put a diesel cluster in. Now, the temp gauge pegs out as soon as I turn the key on ignition. Now I know my truck isn't running hot like that because I didn't even have it running when the gauge was pegged. To make things more complex, I replaced the temp gauge that was in there with another one because I accidentally broke off the needle. The thing that makes me think it isn't the gauge is that the gauge that I broke the needle off of pegged out as well. The only one that worked was the one from the cluster for gas. I know the temperatures are different on the two, but it's only by 20 degrees.

My question is.... is the wiring different? Is it likely that I have a faulty gauge? Or sensor? I just don't want to start throwing parts at it until I can figure out which part it is, and I don't know much about these gauges.

Thanks for the help!

 

[crazy4offroad]

He probably has the gas motor temp sensor in place, and the diesel temp sensor has different ohm requirements, making it read weird. You could try getting the temp sensor for the diesel engine, but if it worked before why even change it?

 

[sonicbluezx3]

I picked up a diesel gauge cluster from the junk yard a while back and installed that one in place of the gas one. I sold the gas one like a dummy before checking to make sure everything worked.
I talked to the guy I bought the truck from and he said the temp sensor is the one that was already in the 6.2 (so it should be for a diesel)..... so I'm wondering if there is a wiring issue or something with the cluster. Seems odd that it would happen after I swapped the cluster out. Is there a way I could test the gauge by pulling it out of the cluster? I would think if I ran 12v to it it would peg out, so maybe I would need to run a different voltage by using a resistor or something.

 

[89Suburban]

I picked up a diesel gauge cluster from the junk yard a while back and installed that one in place of the gas one. I sold the gas one like a dummy before checking to make sure everything worked.
I talked to the guy I bought the truck from and he said the temp sensor is the one that was already in the 6.2 (so it should be for a diesel)..... so I'm wondering if there is a wiring issue or something with the cluster. Seems odd that it would happen after I swapped the cluster out. Is there a way I could test the gauge by pulling it out of the cluster? I would think if I ran 12v to it it would peg out, so maybe I would need to run a different voltage by using a resistor or something.

Just for the hell of it, check this thread out. You got an ohm meter?


http://www.gmsquarebody.com/forum/showthread.php?p=112498#post112498

 

[oneluckypops]

I picked up a diesel gauge cluster from the junk yard a while back and installed that one in place of the gas one. I sold the gas one like a dummy before checking to make sure everything worked.
I talked to the guy I bought the truck from and he said the temp sensor is the one that was already in the 6.2 (so it should be for a diesel)..... so I'm wondering if there is a wiring issue or something with the cluster. Seems odd that it would happen after I swapped the cluster out. Is there a way I could test the gauge by pulling it out of the cluster? I would think if I ran 12v to it it would peg out, so maybe I would need to run a different voltage by using a resistor or something.

NOPE do NOT run 12 volts to it. The temperature gauge works from a 1 wire ground circuit. Most likely the pin in the connector where different from the gas cluster to the diesel cluster. Its actually not hard to fix that if thats the case. But a quick test to determine if its the sending unit would be to unplug the sending unit. With it unplugged (open) the gauge should read cold, if you touch the sending unit wire to ground (closed) the gauge would read HOT. so your signal wire could actually be crossed up with an acrual ground wire.

 

[sonicbluezx3]

I see. Ill try that. Now i need to find the sensor... I heard it is located on the driver side head towards the front just havent looked close yet.

 

[sonicbluezx3]

Okay I replaced the sensor but I messed up the connector in the process. I am going to replace that this week some time, but I think I figured out my problem.

I went to the junk yard to try to get another gauge and only found one (out of an '81) but it didn't fit. But it made me notice something. See pics for reference.

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<< This is my gauge cluster

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<< Front of the gauge I had in there (you can see it's pegged even when unplugged. The needle doesn't move at all)

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<< Back of the gauge. Notice there is an extra connector on it that my gauge cluster doesn't have provision for. Anyone know what is up with that?

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<< The one I got today from the junk yard

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<< Back of it.

So I'm thinking that other pin has something to do with it. If I knew what the pin did I'd try to hook it up, but I think the best option is to just find the one with 3 pins that fits.

 

[crazy4offroad]

2nd gauge is oil pressure not temperature??

 

[sonicbluezx3]

Yes. First one is temp second is oil pressure.

 

[oneluckypops]

Okay I replaced the sensor but I messed up the connector in the process. I am going to replace that this week some time, but I think I figured out my problem.

I went to the junk yard to try to get another gauge and only found one (out of an '81) but it didn't fit. But it made me notice something. See pics for reference.

You must be registered for see images attach

<< This is my gauge cluster

You must be registered for see images attach

<< Front of the gauge I had in there (you can see it's pegged even when unplugged. The needle doesn't move at all)

You must be registered for see images attach

<< Back of the gauge. Notice there is an extra connector on it that my gauge cluster doesn't have provision for. Anyone know what is up with that?

You must be registered for see images attach

<< The one I got today from the junk yard

You must be registered for see images attach

<< Back of it.

So I'm thinking that other pin has something to do with it. If I knew what the pin did I'd try to hook it up, but I think the best option is to just find the one with 3 pins that fits.

Temperature gauge has 3 terminals.
1 12 volt terminal
1 ground terminal
1 signal terminal (from the sending unit)

You can easilly find out what terminal does what with a test light.

With the key on back probe the terminals in the main connector that plugs into the circuit board. Label which ones are power wires and which ones are ground wires.
NOTE: to find a ground with a test ligh just hook the clamp to a KNOWN power supply then use the probe to check for grounds.

After you find out which wires are powers and grounds trace them out on the printed board.

 

[sonicbluezx3]

So what is the extra terminal on that gauge then?

 

[crazy4offroad]

It's just a peg, like a bolt to hold the gauge together, I wouldn't worry about it.

 

[sonicbluezx3]

Okay that's cool. Couldn't tell.

 

[sonicbluezx3]

2nd gauge is oil pressure not temperature??

Ha I just realized I posted the wrong picture on there. I'll have to fix it when I get home. My bad.

 

[sonicbluezx3]

Okay so I just got the new gauge and I feel like a dummy.... it's not the gauge. It's not the temp sensor. So it's gotta be the wiring. I really thought it was the gauge because I pulled it from a truck where water had gotten into the gauge.

I was looking at the printed circuit and it seems to be fine.... just doesn't make sense to me that it all worked before with the other gauge cluster and then when I put the new gauge cluster in, it quit working. Doesn't seem like that would be a wiring issue. The thing I'm wondering is if the wiring for the printed circuit is different on the gauge cluster than it was on the gas one. Gas one was 86.... the new one is who knows.

Does anyone have a wiring diagram so I can trace these wires out? I can trace them to the connector but I don't know where they go from there.