Fluctuating coolant temp needle...

[Om1kron]

Well I noticed last night for the first time my oem coolant temp sensor needle fluctuates. I was at a stoplight yesterday and the needle went all the way down like it was cold.

Gave it some gas and it went back up to where it was, I checked my after market temp gauge and I was holding a steady 75-80 So I know it's not a coolant leak.

I stopped and checked for leaks but there were none. I've been having a fluctuating idle recently and read a how to on how to boost my coolant temp sensors ground to fix that. I wonder if this is directly related to a bad circuit.

Any suggestions on where to look are most appreciated. I'll start with this.

http://zilvia.net/f/tech-talk/190745-irregular-idle-fix-kade.html

And let you know how that turns out.

[Pacman]

My '96 has a fluctuating needle. I've been thinking that the gauge itself is bad but one night I pulled over (steady pace with cruise on at 65mph) and felt the radiator and upper hose. They were warm but I was able to keep my hand on them for a time. That got my thinking that maybe its not the gauge. Any help would be great on this subject.

[awesomenick]

Bleed your cooling system. It's likely that you just have bubbles in it. :wan:

[Pacman]

Bleed your cooling system. It's likely that you just have bubbles in it. :wan:
Havem multiple ways using the bleeder screw opened/overflow adaptor and vacuum method at work. Cooling system is ok, no leaks and bled properly. Will fluctuate if its 105* outside or 34* outside, my cooling panel and GReddy cap installed or stock. Those reasons lead me to believe that the gauge or gauge sensor (the one thats next to the CTS) are bad.

[awesomenick]

In that case, have you tried an aftermarket temp gauge? The sending unit for the stock gauge is cheap if you think it's bad, Autozone sells it. They have it listed as a "temperature switch." You probably already know.

[Addicted2Kouki]

Interesting...I barely ever hear it going all the way down to cold.

I think its just a faulty sensor.
Maybe a bad ground.

If it were bubbles in the cooling system, the temperature would shoot up.

[hustlervibes]

I have a similar problem... or HAD a similar problem. Check the temperature sensor connected to your motor. For me the plug was very loose and causing false readings and a fluctuating needle. Try putting a bit of super gue if that is the case and if that doesn't work get a new one.

[drftthatshit]

^^ummm hello when it comes to your engine temp i would not rely on super glue check your connections there are two sensors on the engine that send signals for coolant temp.....One, is on the intake manifold runner this will be a two prong this is to the ecu, Two, this one should be close to the ecu temp sensor BUT.... it is a one wire this one is for the guage in the dash make sure the connections are tight and working useing a dmm if not just replace both they are not exspensive and can be found any where ^^hack

[hustlervibes]

WTF? Just use super glue to keep it tight, don't glob it on there. It's just there to keep the wires from moving around.

[zero.counter]

Well I noticed last night for the first time my oem coolant temp sensor needle fluctuates. I was at a stoplight yesterday and the needle went all the way down like it was cold.

Gave it some gas and it went back up to where it was, I checked my after market temp gauge and I was holding a steady 75-80 So I know it's not a coolant leak.

I stopped and checked for leaks but there were none. I've been having a fluctuating idle recently and read a how to on how to boost my coolant temp sensors ground to fix that. I wonder if this is directly related to a bad circuit.

Any suggestions on where to look are most appreciated. I'll start with this.

http://zilvia.net/f/tech-talk/190745-irregular-idle-fix-kade.html

And let you know how that turns out.
Check the resistance on the temp sending unit by wiring up the positive side of an ohmmeter to the spade connector on the sensor and then grounding the negative to the chassis somewhere.

As per FSM specs, 60C (140F) should have a resistance of approximately 70 to 90ohms and when the temp is 100C (212F)..approximately 21 to 24ohms. If not within those specs, then replace. Otherwise, check the FSM for the procedures on verifying that the gauges themselves are working. You will need a voltmeter. The issue is usually one of the 2...usually. As long as your harness is still tightly sealed, then the sending cable should not be exposed with any corrosion or grounding occurring, as I have had the pleasure of dealing with in the past.