Heater blows cold until driving then warms up?

Its been awhile since I’ve been on, but a new problem arose the other day. I started my car as usual getting ready to leave for work, and after 20min of warming up I got in, pulled out of the drive, and on my way. I turned the heater on and it was ice cold! Confused, so I checked the a/c button and it was off and the temp was on warm.

The next day I changed the thermostat and powerflushed the coolant system including the heater core. Still won’t warm up until I’m driving. And, even then its luke warm and not hot.

Has anyone dealt with this problem? The car is a 1990 GS with 330k miles.

http://forums.g2ic.com/showthread.php?206991-No-cabin-heat

Your awesome buddy! I’ll be doing some reading and diagnostics this week.

i have a similar problem on my 92 LS with 235k. no heat at idle but as soon as i take off its great. as long as i stay constant it will make me sweat. then its cold again at redlights. my vents move fine, hcv opens fully, and i even replaced waterpump. car won’t overheat, and is full of coolant yet none at idle. worked 1 time after wp install.

probably clogged heater core. when rpm’s rise, it pushes more coolant through. with the heat on, try checking the temp of the inlet and outlet hoses of the core. they should be roughly the same

well back when it got cold,me and a honda tech looked it over and hot water was flowing through both. maybe the fresh pump pushed stuff in. ill have to check, never know i guess… thanks for the input!