[72chevelle350TH350]

I recently got my blower motor working by replacing the inline fuse that goes to the relay on the passenger side of the firewall. I believe it is called a High Speed relay? (the bright orange, 12gauge wire)

Now I only blow air when the dash unit is switched to the max, i.e. three clicks on the lever. this I can live with, I just have to be careful when I turning it on. It really draws some Amps.

SO now I have heat at my feat, but I need it to go to the defroster! On my dash unit I have two sliding levers. One is temp., the other is duct distribution. Which is vacuum? Which is electrical? I know the unit is getting NO vaccum for now. From under the dash I can turn the temp lever and see what looks like the vaccum wheel turning. So I figure me problem is Electrical. THANK YOU FOR THE HELP, The other day I used a squeegy on my inner front windshield! ha!

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[DG]

1 suggestion: Replace the fan switch. It controls the slower speeds using the resistor mounted on the air box (I have A/C on my 70 Malibu). At max speed it bypasses the resistor.

I think I paid $13 from Year One.

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DG
Springfield, Ohio
70 Chevelle Malibu

www.genxspeed.com/dg/chevy.htm [email protected]
TEAM Chevelle Member #0086
Genx member (Founder 4 Ohio)
eBay username: dg98adams

 

[72chevelle350TH350]

What about getting my heat to my windshield via the defrost ducts? I hooked up the main A/C vaccuum that leads to the canister inside the dash. As I switch from vent to heat to defog to defrost, nothing happens. But I switch it all the left to the OFF position the blower will shut off regardless of fan switch position.

 

[DZAUTO]

First of all, make sure you have good vacuum going to your controls. Second, IF your car has heat/air, the blower switch is (or was)still available from Chev (that is why it was so cheap from Year One). The part number is 6273383.

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Tom Parsons

 

[JWagner]

The usual behavior of heaters is to shift to full temp, defrost mode if the vacuum goes away. This is done for safety reasons. If yours will not deliver air to the defrosters, it may be that the door is not working properly or there is an obstruction in the ductwork.I would think that you could manually move the operating linkage for the defrost door and see if you get air at the defroster nozzles. Pulling the top cover off the instrument panel is pretty easy and will allow you to see the ductwork connected to the nozzles.

 

[Morris]

The circulation control is both electrical and vacum. In the far left position all voltage to ac/ht. is cut off.There is a vacum solenoid which operates or controls the air flow to the defrost.It is located on the left hand side of the under dash unit just above the floor circulation portion.

 

[Clark]

Ive had this same problem. This is what I learned.

If you have an A/C car then you have 4 vacume actuators in the car.

#1 is located on the left side of the heater box down near your right foot. This will send air to the defrost ducts or to the floor.

#2 is located on the backside of the heater duct and is almost impossible to see. This one sends air to actuator #1 or to the center dash ducts.

#3 Is located behind the right side kick panel near where your passenger would put his feet. This one will open when "MAX" is selected. It is closed for all others.

#4 I located under the cowl vent screen. You have to open your hood to see this one. This will close when "MAX" is selected.

If any one of these vacume actuators is disconnected or broken then you will have a vacume leak and your selectors will not work.

Also, you should have two vacume lines comming through the firewall near the distributor. One of these lines goes to a valve in the heater hose to stop hot water from getting to the heater core. If the valve is not on the car anymore then you must plug this line. The other line goes to your manifold for vacume. The line to the heater hose valve has a white stripe on it.

The fact that your fan only blows in "MAX" means that you probably have a bad fan switch or your resistor on the airbox is bad.

The fact that the fan shuts off when the slide selector is placed off is normal, it's supposed to do that.

When no vacume is present the system tends to default to blowing a little air every where but mostly to the floor.

Hope this helps, my heater was a big pain in the butt, but is was worth it.

Clark
TC #68

 

[Buddy]

I have no expertise in this area, but from the last 2 chevelles we've own we had to replace the heater motor, and in both cases we cleaned out extreme amount of debris inside the heater box. This greatly helped to put out more air for me. Maybe it was the motor, maybe it was the less debris, maybe it was both? Sorry if this doesn't help