chevy g30 heating problem

Hey guys i have a 88 chevy g30 with a 5.7 L and turbo 300 trans. I am having heating issues with my van. When i am parked it blows warm air just fine and actually pretty warm air. When i start driving it starts to blow cold air does anyone else have a problem like that and is it an easy fix.

Lets get you to the right forum, G-Van below.

First check the coolant temp at running speeds, feel both heater hoses, may have to use a non contact thermometer to do this properly. Possible bad t'stat ,where does the temp gage sit, these are all basic steps to figure this out.

well the hoses are hot and the heat blows warm air when its sitting in park but when you start driving it goes cold i put cardboard in front of the radiator and that didnt help i did not change the thermostat yet

Does the gage go up to the normal range and again what is the actual temp of the coolant, until you have that info you cannot really tell what is wrong.

how do i go about checking the coolant temperature

By the gage, is it lower than usual or a thermometer in the radiator. Or as I suggested above, an infrared thermometer.

More than likely the heater control valve is sticking. If the hoses up to it are hot, its probably bad.

Bob