Temp gauge works! - Team Camaro Tech
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post #1 of 10 (permalink) Old Jan 30th, 12, 03:43 PM Thread Starter
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Temp gauge works!

After many years messing with my console gauges and many searches through previous posts I finally got my temp gauge to work. The key was a post concerning the location of the sending wire & the power wire (I had them reversed). Now the only issue it It reads too hot! I bought a temperature gauge radiator cap & at 180 degrees the temp gauge is all the way over to hot. I have the correct threaded post type sending unit. I'm wondering if I should get a different resistor that is inside the gauge to scale it back to a 1/4 or 1/2 at operating temperature. Thanks for all of the help & advice!

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post #2 of 10 (permalink) Old Jan 30th, 12, 04:02 PM
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Re: Temp gauge works!

Check continuity from the sending unit body to ground. Should be zero ohms.
If sending unit is installed in an adapter, the end is not in the path of coolant.
Once up to temp, disconnect the s/unit wire and measure the resistance of the stud to ground. I remember the ohmic value being around 200 ohms for a 180 indication.
Connect to the disconnected wire, one lead of a potientometer and the other lead to ground and adjust pot to see what value makes for a gauge reading on the first mark, 10 o:clock mark. Subtract the s/unit value from the pot value and get a resistor of the difference and add it in series to the green wire behind the gauge.

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post #3 of 10 (permalink) Old Jan 30th, 12, 04:36 PM Thread Starter
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Re: Temp gauge works!

Thanks Everett. I'll give that a try. Already checked continuity to ground, it is zero. No adapter or teflon,it is in a aluminum head.

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post #4 of 10 (permalink) Old Jan 30th, 12, 05:34 PM
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Re: Temp gauge works!

Not the expert here, but if you have an alum head, the gauge sender has a different temperature coefficient, read different resistance range, than the larger OE temp sender.
This would be why the gauge reads hotter, wrong sensor than OE design.
Alum heads have 3/8 NPT as older head is a 1/2 NPT.
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post #5 of 10 (permalink) Old Jan 30th, 12, 06:17 PM
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Re: Temp gauge works!

Touch the sender lead to ground, should peg hot, then remove ground and it should read cold. If it won't return from hot to cold then your problem is either the resistor on the back of the gauge, should be 86 ohms, or the ground connection on the bottom pin of the gauge. Make sure you have the black jumper wire from one back plate to the other, as there is only one connection to ground in the harness, but both plates have to be connected to it.

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post #6 of 10 (permalink) Old Jan 31st, 12, 09:15 AM Thread Starter
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Re: Temp gauge works!

The head is an edelbrock & the OE type sender screws right in without an adapter. I do not recall the ohm reading of the resistor on the back of the gauge, but I want to say it was 91. Got plenty of time to think about it since I have to work for the second straight weekend

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post #7 of 10 (permalink) Old Jan 31st, 12, 10:40 AM
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Re: Temp gauge works!

If the gauge is a repro, they have (or had) the resistor built in to them, so you may be doubling up resistors which will definately make it read HOT at normal running conditions.

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post #8 of 10 (permalink) Old Jan 31st, 12, 11:13 AM Thread Starter
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Re: Temp gauge works!

Aha! It is a repro. So I guess if I take the resistor out it will read lower at operating temp?

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post #9 of 10 (permalink) Old Jan 31st, 12, 03:01 PM
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Re: Temp gauge works!

Yep, all that resistor does is supply a fixed downward directional force to move the needle towards cold. One would assume it its balanced out at the midpoint of the gauge so that equal forces hold the needle right in the middle. Too much resistance means not enough current in the cold direction so the needle moves towards the hot side of the gauge. No resistance (ie it really does need that external resistor installed) will result in the gauge pegging hot when the car is started and staying there.

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post #10 of 10 (permalink) Old Feb 1st, 12, 11:06 AM Thread Starter
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Re: Temp gauge works!

I'll take it out & see what happens. I've become an expert on taking my console apart & putting it back together!

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