This is for a 2002 Honda civic EX sedan with 186k and 1.7 vtec engine. My wife had to drive to another town 35 miles on a 2 lane highway with air temps in 30s to go to kids dental app. Once in that town it would blow hot air thru the vent. Then, she states, at a light it started blowing cold air thru the vents. When light turned green she would continue thru intersection and the vent would once again blow hot air. Why would the car blow cold air sitting at the light
Correction: this accured after app.
Check the heater topic in the FAQ
Check the coolant level to start. If it’s low you probably have a leak somewhere. If you smell/see coolant I’d check the water pump.
If it’s full or it was low without evidence of a leak burp the system by taking off the radiator cap (while cold!) and filling it to the top. Leave the cap off while it warms up and is no longer spilling fluid. Turn the car off and put the cap back on.
If you’ve made it this far and the problem isn’t fixed it’s almost certainly the thermostat.
