Is the Flow of Heated Air Under Dash Normal?

I don't know of any example where a shut off valve is better. Just as good, but not better. Mopars are the large exception. There are others. The mopar part number is the factory bypass valve.

The warning for heaters is due the lack of circulation with a valve shut. This causes the heater to overheat, and damage itself. Why would anyone have it shut in cold weather? Why do people put hot coffee in a flimsy cup and drive down the road, then blame someone else for the burn? Stupid is stupid, but it's out there.

|UPDATED|6/29/2004 5:58:19 PM (AZT)|/UPDATED|

I just looked in my 74 service manual. The valve to shut off the heater core was used on Chevelle, 116" WB station wagon, and Monte Carlo. I know this valve was added to the Corvette either in 76 or 77, and may have been added to other models as well. It was not a bypass valve, but an open or closed valve that would drive closed when A/C was selected. The valve was threaded into the inlet manifold on the heater core inlet line.

MGBs have a shut off valve. But its feed is not in the primary water cct like a chev v8. Biggest hassle with the shutoff is that with no water circulating, the valve itself tends to gum up and jam. I have to replace mine every few years.

|UPDATED|6/29/2004 6:32:40 PM (AZT)|/UPDATED|

Big Fish said: I just looked in my 74 service manual. The valve to shut off the heater core was used on Chevelle, 116" WB station wagon, and Monte Carlo. I know this valve was added to the Corvette either in 76 or 77, and may have been added to other models as well. It was not a bypass valve, but an open or closed valve that would drive closed when A/C was selected. The valve was threaded into the inlet manifold on the heater core inlet line.

cool.... then I learned something new today

thanks

Like previously stated the manual shutoff valve is replacing the exact design of the automatic function. The benefit of a manual valve is that you are sure it is a tight shutoff in manual. My automatic valve would move but never really shut off tightly and therefore I had warm air in the car all the time.

the shut off balve on Ian wasn't working either, so a lot of hot air was coming into the car. I replaced it with a manual shutoff valve I got at NAPA and it stops the heat from coming in now. There is still airflow but not heated. Th ac is disconnected too. I had get one for a tractor since the hoses are aftermarket steel wrapped and 3/4 inch. Larger than the stck for a car.

Even though my '81 comes from the factory with a valve to automatically cutoff the coolant flow to the heater core when the heat is not turned on, mine must have been stuck open. I took out the factory valve and installed the manual cutoff valve described by so many Vette drivers. Since my car came with a factory valve, I was able to do it without cutting a hose, however the valve is not as easily accessed as it would be toward the top of the engine compartment. Result: MY CAR IS COOL! Thanks to everyone for this great tip!

I was just at the Street Rod Nats. in Louisville and Vintage Air just came out with a electric water inline shutoff valve that was real neat. It has a dial so you can turn the valve on a little at a time. I was lookin at it to put in my 71 as we have the same problem with heat in the car. It's a new product so it isn't in their catalog yet, but if you call them and ask for the electric servo water shut-off valve they can help you. I think they said it was about $75-$85 dollar range. It consist of the valve, the dial,and a small electric box. Check it out, web site www.vintageair.com, may work for you.