I have a 2008 FIT Base with 71,000 miles, that I purchased two years ago with 26,000 on it, hence it saw minimal use for 10 years and now is making up for it.

It’s cold in PA this time a year and even when the engine is up to running temperature, the air temperature coming into the cabin will change from hot to cold, when I decelerate or come to a stop.

Thanks in advance for your help.

 

Have you recently had the radiator replaced or anything like that? First thing I'd do is make sure it's not low on coolant (check the overflow tank: there's an acceptable range it should be within). If that's ok, I'd next suspect that the cooling system may have an air pocket in it, which you could fix by bleeding the cooling system.

 

That'd be my first guess too. Does the air normally get reasonably hot in these cars? Mine works ok except that the air coming out from the vents, particularly central ones, is... like warm at most, even at the maximum setting. My only recent reference is a miata which gets notoriously toasty so I've no idea if this is normall or something might bet wrong.

 

When mine's warmed up I'd consider it hot at the vents. These cars are a bit on the underpowered side as far as HVAC imo, but the heat mine puts out is hot at all vents once the car's up to temp (I just wish the highest blower speed was a little stronger).

 

I have not. I’ll check into these suggestions as soon as I can. Thanks again to all responses so far.

 

Make sure to check the coolant in the radiator not just the overflow. Its possible its just low but other things could be
Restricted heater core (or other cooling lines)
Bad water pump (maybe the impeller was damaged by something)
If its really cold a stuck open thermostat can hurt the situation but your description doesn't really match those symptoms.

Worst case scenario is probably a head gasket putting air into the cooling system but this is rare in the 1.5 or hondas in general.

It does sound most likely that there is air in the system probably from low coolant.