My husband owns a 2005 Honda Civic with 192K miles on it. For the past 3 months, the thermostat has been floating to hot (H). He took it in to a mechanic who could not reenact the problem and could not find anything wrong. The mechanic replaced the thermostat indicator. The problem persisted without any sort of consistency. It would go to hot on the highway when he was going at high speeds and back down again and would also do it while idling at a stop light. We took the car in again and, again, the mechanic could find nothing wrong. Since then, the problem has become more frequent. Additionally, while the AC is on, when the thermostat goes to (H), the A/C is impacted…it starts blowing warm air versus cool. Again, it does not remain this way. A moment later it could go back to the midpoint and the AC then starts blowing cool air again.
Are you referring to the temperture gauge when you say “thermostat”?
If the car is running hot on the gauge then the cooling fan operation needs to be checked. Thermostats control minimum temperature not maximum temperature. If the thermostat is stuck closed then it could cause an overheating problem.
Sounds like you need to find a thorough mechanic instead of one that looks at a car for five minutes and they can’t find a problem so just give up. Most modern cars have a strategy built into the computer that will not allow the A/C to operate when running hot. I also find that a lot of times the information isn’t communicated very well, so make sure when you take it in to be very descriptive about the problem.
Yes - I meant the temperature gauge.