coleaclark1988

ok first of all my name is cole and i live in portland oregon and have a few questions i have a 1992 pontiac firebird and i just replaced heater core and it only blows hot air when im driving but once im just sitting at idle it goes back to cold air so whats the deall does it matter if i had the hoses hooked up wrong on the heater core???

Ward

iTrader: (1)

No, it doesn't matter which way the hoses go on the core. Although, the hose fittings are different size, one is 5/8", the other is 3/4", so the hoses really only fit one way. I would check the vacuum line that goes to the HVAC control, it sounds like it may be leaking vacuum somewhere. In the engine bay, on the passenger side there is a big wire loom on the firewall, and there should be a vacuum line coming out of it. It should be hooked up to manifold vacuum, and it should have a one-way valve. The blend and vent doors in the HVAC ducting are both actuated by vacuum from this line.