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Discussion Starter #1
I've followed the threads and all seems to be OK. New everything and all other gauges work fine. Goes to hot when grounded cold when unhook. When I'm driving the gauge jumps from full hot to the correct reading of just past 1/4 of the arc. I have an after market hooked up seperately and the temp is correct at 190. Any ideas as to why it keeps changing from the correct reading to full hot?

Thanks
 

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A couple things may be happening.
The green wire may be grounding due to vibration.
Sensor may be faulty.
Next time HOT happens, disconnect the sensor wire and observe the gauge;
goes to cold - good wire and maybe a good gauge - stays hot, grounded green wire or bad gauge.
With green wire disconnected, measure sensor resistance from center terminal to engine head - should have some resistance, maybe 200 ohms or such, but not ground.
 

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Thanks, I'll give that a try tomorrow night and let you know the outcome..............
 

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Everett, I pulled the wire and turned to ign and the gauge went right to cold. I hooked the wire up, turned to ign and it went right to hot. I'm not sure what you mean by "but not ground". Could you walk me through the meter test including where best to set the meter.
20M, 200K, 20K etc.
 

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Put your meter on 20K. Touch your 2 leads together. Meter needle should peg or if digitial it should read 0.00 or close to that.

Touch one lead of the meter to the terminal on the sending unit and other lead to a good ground. What does the meter read, should be close to 200 Ohms.

Once you do this set the meter to 200K and see what it reads again.
 

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Discussion Starter #6
Thanks Mike I'll do that after the game..................................................
 

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What Mike and I are suggesting, 200 ohms if sensor is at engine operating temperature, otherwise, a higher resistance value.
The temp sensor has a negative temperature coefficient, meaning when cold, center terminal to ground, using the meter as Mike describes, the sensor will read a high resistance, generally above 5000 ohms.
As the sensor heats up, resistance value lowers, typically, at operating temp of 180°F, 180 to 200 ohms. Just remember, higher temp, lower resistance, closer to HOT indication.
You can get a 100 to 400 ohm resistor, one resistor lead to ground, the other resistor lead to the green wire and see a scale indication. The resistor is a substitution for the sensor/sending unit.
BTW, a TEMP light sensor will not work for a gauge as the light sensor is a switch, HOT, switch is closed, to light the TEMP light.
 

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Discussion Starter #8
Great info and I understand exactly what you mean. Too late to warm the engine tonight though. I bought the sender when I bought the the harness from AAW. It's the correct one with the threaded center terminal. All parts are new. I did have a twist tonight though.
Wire attached-full hot. Took wire off - full cold. Replaced the wire and when I went to ign, it stayed cold. I got excited to no avail. When I started the engine it went right back to full hot. So I'll check the ohms as you describe tomorrow.
 

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Something that I ended up chasing bad grounds /connections around a few yrs back... the glass on the dial is a fraction too close to the needle, and sticks once in a while.
And another , the small nut that holds the tsg on on the top of the sensor has been over tightened at some time, causing a fault in the sensor..
If the above stuff of Everret and Mike doesnt work out , then look at those...bit odd ball but have come across both.. the 2nd not on a camaro thu.
 

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The experience I had was, my 68 Camaro with idiot lights, when driving especially at night with the park/headlights on and dash gauges illimunated, the Temp idiot light would be dim, but would stay on, which was annoying to me. Found out the answer was if you have idiot lights, the temp sending unit that is on the engine (mine is a 350) uses the temp sending unit for idiot lights, and if you are using guages and not the idiot light set up, the sending unit needs to be for when using guages. I found this out when asking for the sending unit at NAPA, Yes there are two different Temp sending units, problem solved when bought the new sending unit to use with Idiot lights. Worked for me, problem solved...This is my personal opion, some may disagree with it......Max in Las Vegas, NV Team Camaro Gold Lifetime Member....Also need to use teflon tape, such as in my case, using an Edelbrock Performer Intake Manifold......................
 

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Discussion Starter #11
Hey guys, something caught my eyes on I believe the CRG forum. It was about the console gauge ground. It stated the other three gauges worked without a ground but the temp gauge did not. He grounded to the trans tunnel and he was good. I have my gauges grounded to the dash. Would that be a bad place to ground?
Sorry I'm not getting back to everyone quickly but I'm only getting about an hour each night to work this out.
Everett, I'm getting .04 ohms from the sender when warm @ 20K. However I really don't trust the cheap meter I have. Because everything is new I can't help but thinking it's some kind of ground problem.
Let me know what you think of the dash ground and if I should add an addtional grd to the tunnel........................ Thanks, again
 

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Dash ground is ground. However, adding another ground to see if the science project works is not a bad idea.
If meter has a lower ohms scale, try it, 2K scale? Another sanity check with meter is measure a bulb filament resistance and see what the value is indicated.
Otherwise, borrow another meter.
 
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