Questions about AC heater vacuum

7173Mustangs.com

Help Support 7173Mustangs.com:

Joined
Jun 17, 2020
Messages
293
Reaction score
368
Location
Homer, Alaska
My Car
1971 Mustang Mach 1
429CJ, 4 Speed, 3.25 Traction Lock N case, A/C, P/W, tilt, fold down seats, int. wipers, deluxe interior.
Was just curious on overall description of normal operation for the heater and controls for my car.

It’s a new heater box (so new doors, heater core, housing)

When it was out I tested all operations of vacuum actuators and they performed as should.

My question is simply what’s normal. I have approx 18 in of vacuum at idle. Line goes into the canister, the smaller line nipple going out of course is much smaller and just doesn’t seem to have the same pull.

When the selector is moved it does I’ve the actuators, but just pretty slowly. I do have an extra canister but I believe it’s doing what it should.

On that subject it’s a canister and a valve right?

So I’m short I wanted to just confirm the whole operation. What got me to look into this was installing a water control valve today and didn’t see it move when put in the cold position. I went under the dash and the small vacuum switch is in place, hooked up properly and functioning. It just seems like I don’t have THAT much vacuum. My next thought was measure going into the tank (which I’m sure is somewhere around 18 in) and then measure the output after. Then measure at an actuator when selected under the dash.

As mentioned before I can move it say from hot to cold or whatnot and watch the door levers move but it just seems really really slow.

Anyways! On a side note I’ve been driving the car a lot! Took it to its first car show and won best of show and best ford! There’s a video on that also.

Now it’s just a matter of small tinkering of things I’m finding. And slowly getting all my AC parts lined up.

Thanks for any tips or notes and help!
 

Attachments

  • 0307BAE1-44A2-43E2-A4FF-560398207918.jpeg
    0307BAE1-44A2-43E2-A4FF-560398207918.jpeg
    5.8 MB · Views: 0
Joined
Sep 8, 2018
Messages
1,800
Reaction score
730
Location
Ross, Ohio
My Car
71 Sportsroof Bright Red.

When you say slow - how slow. They aren't the fastest but should move at a steady rate - perhaps 3 to 4 seconds to open all the way. The canister does have a one way valve but that doesn't really come into play that often other than primarily at low vacuum such as wot and when the car is turned off. You could check the vacuum coming right after the canister and see if it matches your engines. If so, then the problem is inside the car. I had a similar issue with mine and ended up being the control selector switch. It had dirt in it from over the years. Once I dissembled and cleaned it everything it work great.

Here is some info that might help.

 

Attachments

  • AC - Heater Vacuum Motors Testing.pdf
    1.6 MB · Views: 0
Joined
Jun 17, 2020
Messages
293
Reaction score
368
Location
Homer, Alaska
My Car
1971 Mustang Mach 1
429CJ, 4 Speed, 3.25 Traction Lock N case, A/C, P/W, tilt, fold down seats, int. wipers, deluxe interior.
When you say slow - how slow. They aren't the fastest but should move at a steady rate - perhaps 3 to 4 seconds to open all the way. The canister does have a one way valve but that doesn't really come into play that often other than primarily at low vacuum such as wot and when the car is turned off. You could check the vacuum coming right after the canister and see if it matches your engines. If so, then the problem is inside the car. I had a similar issue with mine and ended up being the control selector switch. It had dirt in it from over the years. Once I dissembled and cleaned it everything it work great.

Here is some info that might help.

Haha dude you see that I replied to this awhile back? Haha I thought there was a post talking bout this! Thanks for the link. I’ll dig into it more and let ya know
 
Top