Hello all! I'm having some trouble with my 1990 Accord EX heater. In the mornings I warm my car up and it works just fine at idle and the cabin gets nice and warm, but once I hit the road for work via highway the heater is unable to keep up and it eventually gets cool in the cabin again. At idle the temperature gauge is at normal operating range, but at highway speeds the temperature drops to the cool side. Obviously I would expect the engine to cool a little with all that cool air rushing into the engine compartment at 70mph butI don'tthink mycabin temperature should be dropping this much, I'm pretty much needing to wear gloves inside the car.Any ideas?????? The fan blows fine just luke-warm airon the highway. Once I get off the highwaythecabin will eventually warm back up.Could it be a heatercore or thermostat issue? Thanks.

 

Sounds like a thermostat problem (doesn't close all the way). If it were just the heater core, the temperature gauge would act normal.

 

Thermostat: It doesn't sound like it's closing and allowing the coolant to gain temp again so you've got a constant flow and it just slowly gets cold.... Replace it with a honda OEM one and you should be fine

 

Thanks for the info guys. This a great forum... I'll change out the thermostat (with a Honda one of course) and hopefully that'll solve my problem.

 

Also replace the new gasket that comes with the honda stat

 

Thermostat was changed out and everything works perfectly.... cabin is nice and toasty!

 

Very nice! heat is good! luckily it wasn't a big problem!