Coolant Temp Gauge cutting in and out (1 Viewer)

Joined
Feb 12, 2011
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94
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Columbus, OH
Like the title said, I'm having an issue where the coolant temp gauge in my 94 LC works one minute, and goes dead the next. If I touch or wiggle the plug and harness on the coolant temp sensor directly next to the oil filter, it'll work. If I drive the truck a little bit, sometimes it will cut out.

Seems obvious enough that there's some sort of short or electrical issue. I searched and didn't find anything addressing this, but wondered if anyone had any ideas on how to remedy it, or has a similar experience?

Thanks

-MK
 
Joined
Apr 16, 2006
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1,115
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Cardiff BTS & Tahoe
 
 
If wiggling the connector fixes the problem then it is likely a bad connection at the sensor. However, you need to figure out if it is the sensor or the plug. Remove the sensor and take a look. It might be obvious.
 
Joined
Feb 12, 2011
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Columbus, OH
Okay so here's the next question. What's the best way to get access to it? It's not easy to get your hand on it, let alone see it. Do I need to go from underneath the truck?

-MK
 
Joined
Feb 12, 2011
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Columbus, OH
Thanks. I assume the coolant level in the engine is higher than that sensor hole, and that coolant will come out when I remove the sensor.

I'll probably wait until I flush and fill my coolant (next on my list of baselining fluids) to remove and inspect it.

For now, whatever I wiggled worked, and my temp gauge is operational.

-MK
 
Joined
Dec 14, 2010
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Top of Idaho
you'll lose a little coolant.

deep socket and some extensions will let you get your socket wrench to clear the intake.

make sure you're using the right sized socket or you'll just twist off the wiring connector part.
 
Joined
Feb 12, 2011
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Columbus, OH
Bringing this one back from the dead. After a year, my temp gauge is still intermittent.

I was wrong in my original assessment when I said wiggling the wires at the sensor gets the gauge to work. The two seem to be uncorrelated. Every week or so the gauge will pop on for a day or two, then stop working again. When it pops on and dies seems unrelated to going over bumps, weather, etc.

I'd like to get it working 100% of the time. Any other ideas where it could be getting compromised?

Thanks in advance,

-MK
 

94SRUNNER

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Oct 9, 2006
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Location
Dayton, OH
 
 
So if you move the wires at the senor itself, the gauge functions as designed? If so then you may want to go through the connectors in the plug itself, I think you have a loose/bad connection there. It also could be the wiring, I would take a close look at those as far back on the harness as you can.
 
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Feb 12, 2011
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Columbus, OH
No wiggling the wires has no effect. Originally I thought it did, however the two appear to be uncorrelated.
 

CycloSteve

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Mar 16, 2009
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Stuck between a rock and a hard place
 
 
Did you replace the sensor yet? Unclear from last years' posts if you got that far. Other than that, as said it could be a break in the wires somewhere, or a ground-fault. 99% of the time this sort of thing is at one end or the other (sensor or gauge).

:cheers:

Steve
 

aim

Joined
Dec 22, 2004
Messages
485
Location
Western MA
 
 
 
My coolant temp gauge usually displays the correct temperature, but occasionally dips down to zero. When it does, it'll stay there for 30 seconds or so, twitch to 1/4 a few times and then display correctly again. Turning the CDL (and F/R diff locks) will trigger this condition. ECT use, possibly high beams, etc., occasionally trigger it as well.

The best suggestion I came across was tightening the screws holding the gauges to the cluster, since these screws carry the ground. This sounds reasonable in my case, since the problem started after the RavenTai mod (my solder joins are fine). I haven't checked this, since it's 0F outside right now and I am not very motivated to take my dash apart yet again...
 
Joined
Feb 12, 2011
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Columbus, OH
I finally found a resolve for this problem, and wanted to post it in case anyone searched for this down the road.

What I found was that the 80 has two temperature-related sensors. The single wire sender for the gauge which is above and to the left of the oil filter when viewing the engine from the drivers side, and a two-wire ECT sensor which relays the engine coolant temperature to the ECU. There are two sensors above and to the right of the oil filter. The first one is a knock sensor. To the right of that is the ECT sensor.

I first replaced the ECT sensor, because I was having a stumbling at idle and after covering all the bases there, was directed to the ECT sensor. After replacing this, my gauge was still inoperable. I replaced the one-wire sender last night, and the gauge works perfectly. I always figured a sender would simply fail, not work intermittently. In any event, the sender was pretty cheap (~$27 IIRC), and was simple to change.

-MK
 
Joined
Oct 4, 2019
Messages
12
Location
New Hampshire
Bump for this old thread

trying to find the part number for the single wire ECT sender gauge. I have a 1996 FJ80

Thanks
 
Joined
Jul 26, 2014
Messages
72
 
Don’t know the part number but just FYI my issue was solved by mending a broken wire At the connector for whatever it is worth.
 

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