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post #1 of (permalink) Old 02-27-2003, 01:49 PM Thread Starter
 
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Temp Gage Reads Too High

I just installed a new speedometer cluster from JC Whitney in my 66 JC. At operating engine temperature the gage indicates almost to the Hot mark. I know that it's not actually running that hot because I checked the radiator hoses, radiator and engine block with an infrared thermometer and didn't get anything over 175 degrees. Even the old temp gage read a little on the hot side but the new one even more so. I installed a new sending unit about 2 years ago. I'm thinking about installing a resistor in the wire between the sending unit and the temp gage but don't know what resistance (Ohms) I need to get.

Thanks.
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post #2 of (permalink) Old 02-27-2003, 02:03 PM
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Re: Temp Gage Reads Too High

Usually, the voltage reg in the fuel gauge is off and gives false high temp readings. I had the same issues with a new fuel gauge. Mile Hi Jeep Rebuilders helped me with this problem over the phone. Good luck and keep cool,


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post #3 of (permalink) Old 02-27-2003, 03:18 PM
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Re: Temp Gage Reads Too High

Run a ground wire directly to the speedo cluster. With a bad ground, the fuel gauge goes to empty and the temp gauge shows full hot.
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post #4 of (permalink) Old 02-27-2003, 04:13 PM Thread Starter
 
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Re: Temp Gage Reads Too High

Taz, thanks for the suggestion but I really don't think that the ground is the problem. The illumination lights work, the gas gage indicates 2/3 full (which is about right) and the temp gage starts at cold and slowly goes to hot but not all the way to the "H" mark.

I suppose that it could be a faulty sending unit. I could check the resistance of the temp wire. Does anyone know what the resistance range should be.
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post #5 of (permalink) Old 02-28-2003, 01:12 AM
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Re: Temp Gage Reads Too High

</font><blockquote><font class="small">In reply to:</font><hr />
but I really don't think that the ground is the problem

[/ QUOTE ]1. If you only think it's not the ground, you could be wrong.
2. Take a jumper and run a good ground to the housing...
3. Then you'll know for sure.
4. Remember if the ground is bad, it's like adding resistance to the sender.
5. That can cause problems...
7. For CJ Gauge wiring hints check out: Jaffer's Jeep® CJ Gauge &amp; Sender Diagnostics .

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post #6 of (permalink) Old 02-28-2003, 11:06 AM Thread Starter
 
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Re: Temp Gage Reads Too High

Thanks for the replies so far. Since there were 2 grouding opinions, I went back and ran a wire from the tub directly to the cluster housing but unfortunately, no change. I should add that this is an aftermarket cluster, not the OE unit. The fuel and temp gages do not appear to be grounded; they are plastic and simply snap into the cluster. Also, the fuel gage only has 2 terminals compared to the OE's 3 terminals. It looks to me like it has a solid state voltage regulator versus the OE's mechanical regulator.

Thanks for the link. It has the Ohm specs. The next thing I will do is check the resistance of the sending unit at the block and see if it is within specs. The article says that resistance goes down as temp goes up. I would think that if I had a problem with a bad electrical connection, I would have the opposite problem and the temp gage would stay in the cold range.
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post #7 of (permalink) Old 03-01-2003, 12:40 AM Thread Starter
 
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Re: Temp Gage Reads Too High

It looks like it's a faulty sending unit. With the engine at normal operating temperature, the resistance of the sending unit was 18 Ohms. According to the article, 18 Ohms is the high end of the green band on the gage and that's exactly what the gage read. Now I have another problem. The speedometer needle "sticks". I'll have to send that cluster back to JC Whitney... [img]images/graemlins/mad.gif[/img]
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post #8 of (permalink) Old 03-01-2003, 04:57 AM
 
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Re: Temp Gage Reads Too High

I don't know the specs of your 1966 system, but if you use that later style replacment cluster and/or gauges you need to use the newer era's sender type.
I'm glad my article helped you diagnose the problem.
Chalk up another one ... [img]images/graemlins/grin.gif[/img]
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post #9 of (permalink) Old 03-01-2003, 06:21 PM Thread Starter
 
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Re: Temp Gage Reads Too High

Jaffer, thanks for the suggestion. I'll just use a 72 or later sending unit. And thanks for the article also. It is very well written and has excellent information. I've printed it out and will save it in my technical library.
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