1994 Accord Coupe Ex w a/c. The heater is only blowing warm air. The antifreeze is full and good to -40*. Today at times the temperature gauge went down to nothing and then came back to operating temperature. Any thoughts.

 

How's your thermostat? It kinda sounds like a bad thermostat, bad waterpump, or clog in one of your heater hoses.

 

It can sometimes do that if the Coolant system's level is either low, or an air bubble has formed in the vicinity of the Coolant Temp Sensor. It becomes uncovered.