Backstory in case it’s relevant, but my question is only about the gauge problem, not the overheating problem (unless it’s all related):
I’m currently replacing different sensors and whatnot to try to diagnose why my cooling fan only works intermittently. It only comes on maybe 10% of when it should (when it’s hot and running, when it’s hot and the key has been removed). There have been a half dozen times the gauge has crept up to 3/4 before I caught it and turned the car off, and that all makes sense since the fan wasn’t working at those times. So I’ve never worried that the gauge reading wasn’t accurate until the other day when the overflow tank overflowed. The temp gauge never went above the normal just-below-halfway mark. Then I noticed this (the clicking noise is me pressing the sunroof button):
And also this one. When I turn the car on after it’s already warm, it springs up to the current temp, as opposed to slowly rising up like every other DA I’ve owned.
Whenever I see weird electrical stuff like that, I check the terminals on the battery are in good condition (i.e. not corroded). Also take a look at the grounds that are near the battery (including under the battery plate). Have you messed with anything behind the gauge cluster? Have you checked your thermostat? Did you air-bleed the cooling system properly?
In diagnosing the fan problem, I started with checking that the fan was operational (yes), then moved to the relay (working), then replaced the engine coolant temperature sending unit (still no change), and then finally it was the temp switch in the thermostat housing. I forgot what it’s called. That was replaced the day after my original post, and the fan is working perfectly now. I think maybe the overflow reservoir was just overflowing because the radiator cap was releasing pressure too soon, as opposed to it actually overheating. That would mean the gauge is still giving me correct information. I’m replacing the thermostat and radiator cap this weekend with Honda parts, just as a precaution. My mechanic just did the timing/water last week and I assume he bled the system properly, but the “springy” nature of the gauge has been there since I’ve owned the car. I have never removed the cluster. The battery terminals are clean. I’ll check the grounds. Thanks for the direction, Neil!
Which sensor?
You guys are seriously invaluable. Your input is appreciated more than you know!
It’s the coolant sensor. It’s been awhile, but if I remember correctly it is on or near where the thermostat housing is on the engine (near the distributor).