420A Temp Gauge not working

[Fabri]

I just got a 99 Eclipse GS but it was sitting for 5 years. I replaced both the coolant sensors and the thermostat. But when idling temperature was going up really quick and the fans wouldn’t turn on but when I drive it starts dropping down and the fans sometimes turn on. The gauge never reads below the middle even on cold start.

My solution for it not to read super hot has been turning the hot air on but that only drops the temperature a little. Any help please.https://www.youtube.com/watch?v=dFM9B4bDXyA

 

[dwb]

Hard to say if this is a coolant flow, airflow, or some other issue.

You mentioned your fans are not turning on all the time. I know a 1g radiator has a coolant temp sensor in the bottom that controls one fan, but not sure about a 2g. Might be worth investigating. Do you have A/C still installed? If so, do the fans turn on when A/C is on? You definitely need to make sure the fans are working properly, but lack of coolant flow can also attribute to the fan not turning on (cold spot at the sensor).

Did this issue occur before thermostat replacement? When it's up to temp, does the upper radiator hose get hot at the radiator inlet, indicating open thermostat and coolant flow into the radiator?

I'd start by verifying coolant level is full and that the system is not leaking. Try to 'burp' it, then top off as necessary. If no better, do a full drain and flush of the coolant system.

Beyond that, do a leak down test and see if you have bubbles escaping the coolant system indicating a headgasket issue.

 

[Fabri]

Thank you I appreciate your help, I do have a/c and the fans do turn on. The issue started after the thermostat and new sensors. I think the coolant flow is good I’m going to try to flush the coolant I did see a small leak on the hose near the thermostat so ima see if the fixes anything. Again thank you

 

[Sirius1995]

Thank you I appreciate your help, I do have a/c and the fans do turn on. The issue started after the thermostat and new sensors. I think the coolant flow is good I’m going to try to flush the coolant I did see a small leak on the hose near the thermostat so ima see if the fixes anything. Again thank you

Also check if your coolant has elctrolytes, take multimeter set it on 12V DC and put positive lead in the coolant and ground to your battery ground, should read less than .3V, also perform this twice, one on idle and and one 2000rpm, if it reads more than .3V your coolant is bad and that will start causing issues

 

[dwb]

The issue started after the thermostat and new sensors.

Thermostat installed right side up? Was there something wrong with the original sensors?

 

[BLACK'98DSM]

Due to the design of the water neck, the thermostat cannot be installed backwards.

 

[Fabri]

So I think I found my issue I got an obd2 scanner and it’s giving me P0118 which apparently is voltage too high in the sensor. Atleast I think this is one of my problems so how would I go about reducing the voltage?once again thank you for all the support

 

[Sirius1995]

So I think I found my issue I got an obd2 scanner and it’s giving me P0118 which apparently is voltage too high in the sensor. Atleast I think this is one of my problems so how would I go about reducing the voltage?once again thank you for all the support

Check resistance at 68°F and see if it's out of specs, should be around 2690 - 2210 ohms

Resistance rises when temperature increases and vise versa.. it's 5V sensor so you can also measure that you'll get 5V to connector