I noticed my temp gauge was stuck below C today, on my way to an appointment. On my way back, it was initially stuck at C but then started bouncing from C to the middle, and then stopped way up at H, by the end of my drive (about 20 minute drive). See video below, sorry for the horrible quality.

I don't (yet?) suspect the engine is overheating. No smoke or smells. The interior heat was blowing hot.

I have an OBD2 reader on order, which should be delivered in the next couple days. So I will be able to check the engine temp, once I get that.

Any ideas on why the gauge is bouncing? Or what to check? My first guess is that this is an electrical problem, or faulty instrument cluster. But I haven't done any troubleshooting yet.

 

What year is this accord? V6 or 4-cylinder?

 

1998 Accord EX Sedan 4-cylinder

 

Your accord has two separate temperture sensors. The ECT only sends the temperature signal to the PCM. The engine coolant temp sending unit only sends a signal to the gauge you see fluxuating. Your issue can be the the ECT sending unit, the wiring, or the temp gague/cluster.

The easiest test is to unplug the connector to the sending unit, make sure the connector doesn't touch ground, turn the key to the II position, and see if the gauge stays at zero. The sending unit is the sensor bolted to the cylinder head below the distributor with only one wire connected. If you have an assisant, they can ground the unplugged wire, then the temp gauge should rise to H. Do this test quickly, because having the gauge pegged at H for exended periods of time can damage the gauge mechanism.

If the gauge sill acts up when doing the two tests, most likely issue is the solder joints on the gauge circuit board for the coolan temp (I suspect this is your problem). If the gauge behaves normally, then replace the sending unit.

I doubt you have a real overheating issue, but you should check the ECT readings, because real overheaing can cause damage the engine and be very expensive to fix.