hey guys, i have a 99 accord dx, i noticed the temp gauge would drop to cold and fluctuate while driving, but the needle would never go up pass the normal mark, or go the H. I replaced the thermostat yesterday, and the temperature needle still drops to cold while driving. after the thermostat replacement i let the car idle and the temp gauge went up to the normal mark, and also the fans turned on. So I thought everything was ok, until i went out for a drive and i still had the same symptoms. Could it be the sending unit? please help!

 

update: replaced thermostat again with an OEM honda part. still have same symptom. heater blows out hot air, let the car idle/bled the coolant for over an hour, fans turned on about 4 times.

temperature gauge took forever to get to the normal mark.

went for a drive and then the needle dropped to Cold again.

any help please! is it the ECT sensor under the distributor? or the sending unit?

 

The gauge is actuated from the single wire sensor under the distributor. If you have a decent OBD2 reader, you can set it up to read instant data, and it will give an actual ECT reading(what the computer is getting). If it shows normal, 195-200ish, then suspect the gauge sensor. If not, then theres another problem.

 

does your heater still blow hot while driving and the gauge shows cold?

 

I've got a similar problem on our odyssey, except the temp gauge just won't move at all. Heat works, fans work, just nothing from the gauge on the dash at all.
Following this.