A few days ago i posted about my car heating up and the fan not working... Ive seemed to find the problem because i replaced my thermostat and the fan now works .. The car runs fine and the top hose gets really hot and the bottom hose stays just warm which tells me the radiator is circulating. So everything seems to be working fine but every now and them the gauge will go to three quarters and i dont belive it is supposed to.. (Im not losing fluid either) . So i shut the car off and check the fluid but its fine and ill start the car again and itll be at half as it should be.... Could it be the gauge in the car? What are the chances? The tempurature sensor is not releasing an engine code either .. Please help!

 

It's quite possible. It can also be the sensor for the gauge.

If the 2000 is anything like the 92-95, there is 3 different temp sensors on the motor, one for the fan, one for the gauge, and one for the ECU.

The easiest method I can think of to isolate whether it's the sensor or the gauge would be to tie into the wires to the sensor and monitor the voltage. If the voltage is stable while the gauge jumps to 3/4 then it's a gauge issue. If the voltage jumps with the needle, then it's not a gauge issue.

I hope that makes sense.

 

That does make sense thank you! Ill give it a shot!

 

There's only one wire that runs to the gauge. It's a single plug switch, on the head under your distributor. Should be easy to find - it's the only one wire plug there. It's also very easy to accidentally unplug when you're doing other things with the cooling system. Find it, make sure it's plugged in, check for corrosion.

 

Being the one wire sensor, if you don't find corrosion or contact issues it will be a little bit more challenging to setup a monitor for it.

It should be a thermistor and if it's anything like the rest of Honda electricals, it is the ground of the circuit not the hot lead.

The easiest way to determine that of course is to check for voltage between the one wire and ground. Should be zero volts if my suspicion is correct.

That won't be as cut and dry to see fluctuations or the lack of with the needle.

For that situation I suppose you would have to monitor current instead of voltage as the hot side is internal to the cluster for the gauge.

The change in impedance by hooking up an amp meter inline with the sensor will change the home position of the temp gauge.

For all the trouble, might be easier to get a replacement sensor if you don't find any contact issues and swap it out. If the needle still bounces then you can conclude with some confidence that it's a gauge issue.

 

It is a grounding thermistor. You can short the lead to ground and watch the gauges run up towards hot.

I would verify a proper bled coolant system before attacking sensors and gauges as well as the fan switch

 

Solid advise right along with NotARacist advise.

The most likely culprits are between you two.

I was focusing just on the aspect that it could potentially be something up with the gauge as OP had asked and an easy way to rule out the gauge itself. Even though the gauge is much much less likely than anything either of you two posted.

 

Thanks for the help guys I appreciate it ... Im going to go get a hot/cold gauge and fuel gauge out of an ex at the junkyard tomorrow and see if the needle jumps around and go from there ... Might as well start with the cheapest first

 

I'm assuming you've already done the cheapest items of all and checked the connection for looseness and/or corrosion as suggested by NotARacist and also made sure the coolant system is properly bled/burped as well as make sure the fan kicks on (fan switch verification) as was suggested by 92ehatch?

These items don't cost any money just some time....

 

I mean, that thing is stupidly easy to accidentally unplug whenever you're fiddling around near the distributor. It's all on the same loom, too, so pull on one thing when unplugging it, and it might just pop out too, and you'd never notice it.

 

And it plugs on like the OEM oil pressure sender on the back of the block with a little coil within a rubber casing thats likely corroded so its fairly easy to damage as well without realizing it as stated above.

 

I read nothing to suggest that your temp gauge isn't working properly. I also don't see any logic in replacing your gauges at this point. Start by thoroughly bleeding the cooling system like this:

https://honda-tech.com/honda-civic-d.../#post39830585

^This must be done after replacing the thermostat.