Litle to no heat

[Guest my3buicks]

My 69 Electra has little to no heat. Earlier this summer it had the system back flushed, a new heater core, and new a 4 core radiator(up from the standard radiator), a new heater/water control valve, and all new hoses and thermostat. The car does not overheat at all. If I slide the heat control; slide off for a while then slide it back on I get hat for a few minutes then back to no heat. I'm a little stumped on whats going on on this one. Any suggestions?

[Judd]

Kieth

I put a 4 core radiator in my 65 GMC and I have to run with cardboard radiator block off in the winter to get heat. It only runs about 150 in the cold weather unless I am running on the express way. Could you have an air lock in the new heater core?

Judd

[riv2x4]

I had a similiar problem with my 69 but only at idle. The supply hose to the heater core never got hot. If I raced the engine I had better flow and would feel some heat. This all happened when I was flushing the system. When the car was in motion I had all the heat I wanted. Mine too wanted to run around 150 degrees. Mine is a 9K original mile car and is not driven much.

Larry

[Dave@Moon]

It sounds like a bad vaccuum control action. I don't know how accessible the heater door is on a '69, but if you're able to manually move the door linkage and regain heat then you probably have either a bad control diaphram or a bad vaccuum line that is collapsing under vaccuum.

I think the latter is more likely, since the vaccuum control is strong enough to work the linkage in the first place. The line is probably weak, collapsing under vaccuum, and the return tension and/or any air leakage is allowing the linkage to re-close the door. A gunk-ed up or partially blocked line could do the same thing.

[Guest brh]

Check both hoses going in and out of the heater core. If both are hot then your problem is in the dash. If one hose is hot and the other is cool then its a vacuum control problem.

[Guest my3buicks]

did a quick fix for Hershey trip. Pulled the vacuum hose off the heat control valve under the hood and now I have heat!!

[rocketraider]

Keith, I think you have the wrong water control valve. Some of those things are vacuum open, some are vacuum close; most apply vacuum to close only when A/C is on. Also possible the vacuum selector valve on the control head has quit since you say you can cycle the heat lever and it'll work a few minutes.

The 97 Bravada pulled this stunt last Thursday AM in Carlisle. It was working fine and then suddenly no heat, which provoked several unkind comments toward it, but it was working again that afternoon and has worked fine ever since.

The Tempmatic in the wagon shat the bed a couple winters ago and stuck in full cold on a 22 degree morning. Miserable drive to work! I went to a local junkyard and scarfed up every programmer I could find. When all was said and done, I had enough good components to fix the one in the car and have 2 working spares. And got rid of the wheezing and creaking under the dash, which used to scare the bejeezus out of people unused to its antics.