1977 Chevy Nova Heater in AC car w/ no AC

ZAT

MEMBER
1977 CHEVROLET NOVA
V8
2WD
AUTOMATIC
100,000 MILES

My 1977 Nova was an ac installed car but the previous owner(s) removed all the ac equipment under the hood. We cannot get the heater to operate correctly. The fan will run on the low and medium speeds but not the high setting. We also cannot get the heat to flow to the floor vents. All duct work was located and installed. The heater core is present and OK.

I do remember that there was some type of vacuum that operated the vents. Is there a way to get the fan speeds working properly and (at least) prop open the vent to the floor discharge? Will I also need to replace the heater control to a non ac control?
Do I need to replace the heater relay and where is that located?

Thanks.

4 Replies

BUDDYCRAIGG

MECHANIC
2,262 POSTS

Close to the blower motor under the hood, there should be the high speed blower relay.
When you switch the lever to high speed,
this relay sends full battery power to the motor.

So you'll need a test light to check that it is getting power from the battery.
And then is getting power to make it come on when the switch is in the high position.

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Saturday, August 8th, 2009 AT 5:17 PM

ZAT

MEMBER
3 POSTS

Thanks for the info on the relay.

Any advice on the rest of the question?

We also cannot get the heat to flow to the floor vents. All duct work was located and installed. The heater core is present and OK.

I do remember that there was some type of vacuum that operated the vents. Is there a way to get the fan speeds working properly and (at least) prop open the vent to the floor discharge? Will I also need to replace the heater control to a non ac control?

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Monday, August 10th, 2009 AT 7:29 AM

BUDDYCRAIGG

MECHANIC
2,262 POSTS

No I do not have a magic answer for you.

Yes the doors that direct the air flow are operated by vacuum. There will be a bunch of colored plastic lines coming from the heater control head, and going to the dashpots that open the doors.

You'll have to do some testing with a vacuum gauge and figure out what lines go to which dashpots.

Make sure you have a vacuum source going to the heater control head.

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Monday, August 10th, 2009 AT 9:39 AM

ZAT