'71 AC System

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cigarguy

Active member
Joined
Oct 16, 2015
Messages
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Location
Florida
My Car
71 Mach 1, 351 Cleveland
Hey All,

Just bought a 71 Mach 1 that had factory air, but nearly every aspect of that original system is gone besides vents, blower motor and control panel. I'm not sure what you call it, but the metal intake ring or bezel under the cowl that draws in fresh air (directly behind and above the glove box) is completely rotted out.

So my question is.....how necessary is this intake if I go with a Perfect Fit type after market AC system? Do these systems just use recycled air or would I need some type of intake in that same area?

--Todd

 
Besides being the inlet to bring in fresh air the hat also prevents water from getting into the car. With it being rusted out the first time it rains you will have water entering the passenger side of the car and eventually rusting/rotting the floorboard. You will need to fix this. Check out this thread:

http://www.7173mustangs.com/thread-cowl-rust-repair-step-by-step

 
Chris Ingrassia also shows a 'short cut' that avoids removing the cowl upper panel completely. I did consider this but decided to do it as jbojo refers to in 69 Rustang's (love that name) post. Search Chris Ingrassia Rusty Cowl in You Tube for his video, it appears to be a less invasive fix but your plan of attack will also be dictated by the current condition of the rest of your car and if are prepared to strip it back to bare cowl or just do the repair a'la Chris Ingrassia after removing just the fender. Would be interesting to hear from anyone that may have had success with this short cut on a very common problem. I've seen a couple of local otherwise stunningly restored Mustangs that have left the rusty hat because it was too hard.

...Mickus

 
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Great help. My cowl vents are in good shape, but the hat is toast. I'm sort of confused about what is suppose to be on the underside of the hat. Does it go into an AC component? I'm considering an aftermarket AC system, and since they used recycled air, could I just sheet metal over the hole?

 
Think of the hat as a chimney cap. As water enters the cowl it flows around the hat since it has sides and by the fender wells there are drain slots for the water. The hat covers the top of the tube but has space and allows air to enter the car from the outside via a vacuum motor/flap valve when the AC switch is in the Fresh Position. When in recirc this flap closes preventing air from entering from outside of the car. If you buy replacement AC components it will need this hat installed. I imagine that you can just have recirc mode and block off that hole but it could lead to future issues if not done correctly the first time.

 
I think I got it now. The stove pipe damper/flap is what's missing, but it's a component of the non-existing AC system that would mount underneath and be controlled by a vacuum motor.

So since I'm going with an aftermarket AC, would you recommend fabricating a hat and just capping it with a plastic lid or plug in case I decide to go with a factory replacement AC system down the road?

 
I think I got it now. The stove pipe damper/flap is what's missing, but it's a component of the non-existing AC system that would mount underneath and be controlled by a vacuum motor.

So since I'm going with an aftermarket AC, would you recommend fabricating a hat and just capping it with a plastic lid or plug in case I decide to go with a factory replacement AC system down the road?
I looked for some pictures from my build when I replaced the heater core and AC evaporator. In the first pic it shows the vacuum motor that operates the flapper valve to control the air coming through the hat.

The second pic is a view from under the dash looking up through the cowl and the top of the hat. You can see there is a space between the cowl and hat to allow air to flow in.

The 3rd pic is the AC/heater box and at the top right is the opening that connects to the hat. In the opening you can see the flapper vale and its in the open position so that would be the "Fresh" setting allowing air to be pulled in from the cowl. That opening is blocked when the AC is in recirc mode. The bottom right shows the bracket that holds the vacuum motor on pic 1.

You mentioned that your car was an AC car so these parts should be there unless the PO removed everything. You can get the box and other parts as repops to restore the AC system back to original if you are missing parts.

If I were you I would just fix the rotted areas instead of patching it as unless you get all the rust out the rust will keep spreading. They do make repop cowl pieces now so it makes the job a lot easier and you don't have to find a donor car for the pieces. This is a common rust area so addressing it now would be to your advantage especially if you plan on keeping the car.

I have lots of pics of this part of the restoration if you need to see anything else.

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IMG_2091.JPG

 
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