Author Topic: 69 Camaro console water temperature gauge issues  (Read 290 times)

mmotley

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69 Camaro console water temperature gauge issues
« on: May 17, 2020, 12:18:30 AM »
Hi Folks,

Hope you can provide some insights.   69 Camaro RS 4 spd with console gauges.   The water temp gauge will not come off cold regardless of engine temperature.   When the sending unit wire disconnected and ignition on the gauge goes to full cold.   With the sending unit grounded to battery and ignition on it goes to full hot.  This leads me to presume the gauge is ok and the wiring is properly hooked up.   I've cleaned all connections, confirmed ground, replaced sending unit, confirmed resistor on back of gauge is 85 ohms.   Resistance on the sending unit drops as engine temperature increases.   Here is the kicker - with the engine running and warm the gauge is at full cold - turn off the engine and ignition off and the gauge will begin creeping up.   Turn the ignition back on and it goes to full cold.   It makes me think I've got a short in the system somewhere and I'm getting battery voltage even with the key off.   I am not an electrician and have no idea if that makes sense.  I would think if I have a positive short things would melt or pop fuzes... but there is no way an electric gauge can move without electricity.  I'd appreciate any thoughts or suggestions you folks may have

thanks
Mike

firstgenaddict

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Re: 69 Camaro console water temperature gauge issues
« Reply #1 on: May 17, 2020, 03:20:57 PM »
Sounds like you have an idiot light sending unit.
Have you checked the range of output from the sending unit using an ohm meter?
Does the output incrementally change or is it OFF or ON.
James
Collectin' Camaro's since "Only Rednecks drove them"
 
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169INDY

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Re: 69 Camaro console water temperature gauge issues
« Reply #2 on: May 17, 2020, 06:00:09 PM »
James is on the right track; Start with the Grounds at the console make darn sure they are good.
Then like James mentioned set up an ohm meter on the sender, Disconnect the harness green wire, Hook Red meter lead to the pin and black meter lead to chassis or eng ground. set  the ohm meter to read OHMS
In general terms:

Cold <400 ohms
Mid= 100 ohms
Hot around 50 ohms
These values are a ROM (Rough Order of Magnitude) i.e. approximate (* I can not recall where I source these values)

Start the car and warm it up observing ohm meter and monitor temp using a harbor freight point and shoot thermal device.

https://www.lectriclimited.com/electrical-devices/temperature-sending-unit-110014

If you get REAL fancy you can source a 0-500 ohm potentiometer and make a sender simulator.

The intent s to determine "IF" your sender is a variable resistor with inverse proportional resistance to temperature. See the temp increase the resistance decrease -vs- a std dash light "Switching" sender that is Open (Infinite ohms) cold and Closed (Zero Ohms) hot.
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

mmotley

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Re: 69 Camaro console water temperature gauge issues
« Reply #3 on: May 18, 2020, 12:08:45 AM »
Thanks for your help guys!!!

Clip on top - not threaded.   Stone cold it is 142 ohms - so pretty sure it not an idiot light otherwise it would read open.   I will crank tomorrow and check resistance as things warm up.   What about the gauge creeping up when the ignition is off?  Makes no sense to me.   I read though a crap load of forums and didn't see any issue similar to this.   

169INDY

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Re: 69 Camaro console water temperature gauge issues
« Reply #4 on: May 18, 2020, 02:44:44 AM »
I have a email to Lectric Ltd, & Found a Instrument Panel - with gauges color diagram dtd 2005
WATER TEMP SENDER
390 Ohms at 100 degree F
102 Ohms at 260 degree F

Your Stone Cold (Ambient garage temp) resistance seems out of wack?
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS