Everyone was so helpful with my last post so I figured I try my luck with this one.

I read through similar issues but they weren't exactly the same.

OK here it goes, 92 Maxima.

Just had the thermostat changed and at highway speeds the heater pumps really hot air. However stop at a light or at low speeds the air is just warm. Speed up and everything is fine again.

Any suggestions; when I'm stuck in traffic I'm freezing my *** off!

 

Did this start right after the thermostat change? Mine did the exact same thing and I have not been able to figure it out. The only thing that I can think of is a plugged heater core.

 

Whoa, everyone usually has the exact OPPOSITE problem from you... Hrmmm, not sure if this is the case or not since I can't quite picture the correct way that it goes in, but did you put it in backwards?
I know on my VG it will fit both ways... Because we put it in backwards the first time, looked at the picture in the manual and did a Homer Simpson...

 

I have the same problem. Replaced the thermostat this summer cause it was happening last winter too. Not sure what it is.

 

My guess as to why the heat would increase at higher speeds would be water flow increase. I would flush the system and see what happens. That is also cheap.

 

I have the same problem too...i just replaced the stat as well...

after looking at the whole heating/water circulation system and testing it, my mechanic says something is restricting the hot water flow through the heater core while at idling speed, since at higher rpms, the water flow and pressure increases, the heat comes back on while driving.

he disconected the input and output pipes at the heater core and attached a funnel at the intake pipe, poured water down the hose and it came out like a trickle out the output pipe. we did a low pressure reverse flush right then and after some crud came out the input hose, water flow became normal. he didnt have a water hose at his shop so we couldnt do a proper reverse flush.

i am thinking of reverse flushing my heater core after pouring in radiator flushing liquid through the intake hose. just cant find a place to do it cuz of the really low temperatures outside.

 

But to get at the heater core, don't you have to take apart half the dashboard? Seems like a lot of work to do a reverse flush.

 

NOPE...u can do the flush just using the input and output pipes by the firewall in the engine area...u dont have to touch the dash and the heater core does not have to be taken out at all.

 

is the water pump, therma stat and belts all next to each other
my macanic said that my belts are going out so im thing bout doing the pully upgrade and my water pump is leaking would it be cheeper to do all this at once

 

correct me if i'm wrong, but won't a water hose be to small to fit in the output pipe in order to get pressure to build up to force the water (flush) back through the core and whatnot???

 

i dont think so....the output pipe on the heater core is pretty thin actually...its the one coming out from the firewall. i'm guessing the hose might be a bit LARGE for it..

i still havent been able to do it cuz of the constant freezing temperature outside. i'm waiting for a "slightly" warmer day.