77 heater controls non ac

[Frank K.]

What controls the blower motor ? Mine runs all the time producing heat after I changed the heater core. Thanks

[Edward J.]

Re: 77 heater controls non ac

Frank is the blower running on high speed all the time?

[Frank K.]

Re: 77 heater controls non ac

No just running. Like at a low speed. Have no control at levers on consul. Had to pull power feed at blower on firewall to stop blower.

[Alan D.]

Re: 77 heater controls non ac

The 1977 Corvette does not have thumb wheel but a temperature lever. When the lever is all the way to left the temperature should be cool and when moved to the right the air temperature is heated. I will have to check if there is a hot water shut of valve on a non-air conditioned car.
Al Dieterle

[Edward J.]

Re: 77 heater controls non ac

Alan, since the heater box was out, is the adjustment on temp door okay? If your corvette is one of those cars with the fan motor always runs in low it should be addressed in the owners manual. Hopefully it not something to do with the seal on the temp door.

[Alan D.]

Re: 77 heater controls non ac

Alan,
I looked at the vacuum diagram in the AIM for a non-ac car and there is a water shut off valve shown. If this valve is not shut off or missing the heater hose water will flow through the heater core and provide heat all the time. Check to if there is vacuum to this valve when the control selector is in the vent position. In any other position there should be no vacuum. It also could be that the water shut off switch is defective or not adjusted correctly. This switch controls the vacuum to the water shut-off valve.
If you have the AIM for the 1977, the pages 133 and 134 show the vacuum diagrams and the components. Page 128 shows how to adjust the temperature control cable.
Have fun.
Al Dieterle

[Frank K.]

Re: 77 heater controls non ac

I placed vacuum on the water shut off valve and it held with my vacuum gauge Could it be the Cable temp lead? (where ever that is off the manual heat and defrost control)?

[Alan D.]

Re: 77 heater controls non ac

You must check for vacuum at the vacuum control line that connects to the water shut off valve. It is a black plastic tube with white stripe. There should be vacuum at the line that is connected to the water shut off valve when the control selector is in the vent position. If not, the temperature control cable will need to be adjusted according to the AIM manual.
Al Dieterle