Heat to cool to heat to cool.....

[billschroeder5842]

Although is does not get THAT cold in Texas, it gets cold enough for one to want the heater to work properly!

Here is my situation....1969 / 383, new(ish) heater core, new radiator, 165 thermostat on an A/C car. The heater will work on and off meaning that the heat will blow for a while and gradually cool down. If I take the heat/cold slide and move if from heat to cool for a bout 30 seconds then back to heat, I get a blast of heat for a few minutes and it gradually cools again.

I do have a valve (it is open flow now) on the water hoses that go from the engine to the heater core--I close off the water flow in the summer to help the A/C a bit--could that be an issue?

So any ideas?

[Back N Black]

Sounds like you have air in the system, turn the heat on max and remove your rad cap. Rev the engine between 1500 -2000 rpm until you get a constant flow of hot air.

[billschroeder5842]

Thanks-I gave that a try for about 15 minutes....no joy.
Any other ideas?

[John_Kunkel]

Bypass the water valve and see if it improves. (open valve might be restricting the flow)

[A383Wing]

sounds like a plugged or restricted heater core

Bryan