Where to start on heater and blower?

[Brandon Metzger]

I have a '72. The car has AC but I have disconected it for now, other things to tackle. All the electrical system for the heater and blower seem to be connected. However, the system is dead. I am asking for help on where to start? Are there common problems, things I should look at first, etc. I am slowly getting the electrical system up and running but this is the first major electrical issue I have attempted so far.

All fuses are in. This being said I am still trying to figure out if there is a 30A circuit breaker in the top left of the fuse box. My assembly manual doesn't show one but the Chilton manual mentions it, it could just be on later models. All other hoses, relays and valve assyembles seem to be connected.

Are there ways to test the relays and valve asm. or do you just start replaceing?

Lastly, my vaccum system for the wipers and light is shot. I haven't started the repairs on this yet. I mention this because I do not know if it is at all related to the heating system.

Any help to give me a starting point would be much appriciated.

Thank you,
Brandon

[Wayne P.]

Re: Where to start on heater and blower?

I would start with the fan switch. Yes the A/C uses vacuum to operate, so that will need to be functional also.

[Tony Merendino]

Re: Where to start on heater and blower?

I recently had a similar experience on my 70 cpe. After much disassembly it ended up being the ground for the blower motor. The ground wire on my car came out of the wire harness to the rear of the starter and was grounded to the passenger side frame. The wire was broken and when replaced the system worked as intended. I found this out after removing the blower motor and then testing it to make sure it was functional since I had already found a replacement.

You can check the blower motor operation by making sure you have voltage to the live lead and then grounding the blower case. The blower motor should operate while the ignition is set on ACC. This eliminates starting the car and the blower motor can be easily heard without the engine running.

[Brandon Metzger]

Re: Where to start on heater and blower?

Thank you Wayne.

I am currently looking in the Assembly manual from Corvette America, Again for a '72. On page M149 there is the diagram for the "vacuum control hose routing". There are two actuators, on on each side in the rear, that connect to the vacum control asm. in the shift console. There is hose running from the actuator to a pipe that is formed over the wheel well then down behind the seat then along the brake and shift console then conected via hose to the vacuume control asm.

I removed the original carpet this fall and it is still out of the car so I can see everything under the carpet. I have no signs of this, none at all, no hose no clips and no pipe and no acutators. At the bottom of this page it says redrawn & redesigned (GR-1046) on 2/19/72. My car does have AC. Did they redesign this and where did they put it? I am a little baffled because I do not seem to have anything on this page in the assembly manual.

Thank you,
Brandon

[Jack H.]

Re: Where to start on heater and blower?

The line you're looking at is for the Astro Ventilation exhaust louver on the rear cabin wall. Cars with C60 (A/C) did NOT have a moveable exhaust louver (and therefore no vacuum control line) as the rear exhaust vent was permanently 'plugged'.... Turn to option C60 in your AIM book and you'll see the modifications to the Astro Ventilation exhaust louver going onto the car. Plus, you'll find electrical + vacuum system 'extentions' to base car for the addition of A/C.

[Brandon Metzger]

Thank you,

Thank you guys. I found everything and have a much better handle on the situation. Jack, I looked up the info you suggested and it was right on the nose thank you. I am also going to check the ground wire and the motor first to see if this is the problem.

Thanks again,
Brandon

[Jim T.]

Re: Where to start on heater and blower?

Brandon my 70 has a inline fuse for the blower motor. Mine is located coming off a relay on the drivers side fenderwell. Another problem could be the blower motor fan motor console mounted switch. If it is broken on the inside of the switch the fan motor will not work. You can readily tell this by checking that you have mulitple speed selections.
The vacuum system for sure can be a problem. There are relays that are hidden and multiple leaks are possible. Would you believe that when my 70 was new that the vacuum system was so tight that even after sitting overnight there was enough vacuum stored that it would open the headlights?
This procedure will save you a dollar. The vacuum cannister that opens your wiper door assembly has a external seal that can be easily replaced. This seal goes over the shaft coming out of the cannister. A conventional baby bottle nipple, perfer the silicone type will replace a leaking seal. Use a expended 22 shell to cut a hole in the nipple and just install it. This idea was obtained from a Vette Vues article I read many years ago. My silicone nipple replacement has been in use for about 15 years. The factory accordian stype rubber covering hides it from view.