Truck has no heat while driving down the road ... why? on 1995 Chevrolet Tahoe

I just picked up this truck and has no heat I changed radiator cap and thermostat but did nothing has heat at idle but loses it as you drive down the road was told it could be a number of things like heater core... water pump.. bad head gasket... well I eliminated the head gasket so far the system pressure checks good but I have no heat... the passenger side vents don't work when the heat is on but if I turn the ac on they vents work.. but there is a lot of air blowing around the blower motor area.. please help

Asked by for the 1995 Chevrolet Tahoe
Have it checked by a mechanic!!
2 more answers , 9 more comments
what temp therm did you install? poss blockage in heater core heater control valve is bad
I just picked one up from the nearest parts store I have to Tahoe's 1 is a 95 and the other is a 99 and they both run at the same temperature which is 180 degrees
i think it should be a 195 if im not mistaken.where does your temp gauge read?
It reads in between 100 and 210 like directly in the middle of that
Does the engine temp increase when driving? Could have water pump impeller issue thus not properly circulating the coolant.... If engine temp lowers while driving you may be missing the thermostat causing the coolant (antifreeze) to cool to quickly. Although it could be a number of other possibilities or combinations. I'm local if you have any further questions.
The tempo goes to almost 210 and the thermostat opens and it drops to 180 and stays there... if you start driving the temp drops a little past 180 but is you stop its goes back up to 180/190 area and then I have heat
ASE Master, define local. Your in WI, the vehicle is in NY!
Not too sure why it says that I'm from a little town called ancramdale ... new York state lol
Wondered about that myself. I guess you have needed that heater lately. Here in VA too!!
Sorry guys, I mixed locations with a previous..... It sounds low on antifreeze by thr 30 degrees difference of opening and running.... I agree with Pushrod, have it checked out!! The temps lately have been brutal! Hope we all get warm weather soon
No problems, except the heater of course!
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