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Heater Box
#1
Does anyone have text that explains the heater box vacuum lines and all the devices that are attached? Scott sent me a diagram that shows the vac lines and it had some text explaining what each vac sensor does when its activated but it was only 1 page. Basically I need to know how each flapper opens and closes and what each device on the box does. I'm in the process of rebuilding it and am probably going to have to troubleshoot it once it gets reinstalled. It is an ac box

Thanks,

D. Rolls

Chasing Rust
  Reply
#2
urg i knew this 3 years ago.

I'm having internet issues,,, let me get back to this tonight when i get home. if nobody answers this I'll come back and post pictures and the diagram.



  Reply
#3
OK, my internet is Slow and craptacular today.

Here is my write up.
-------------------
Link to my photos of rebuilding a heater A/C box
http://s1031.photobucket.com/albums/y377/72hcode/Heater Box AC/
----------------
Reference this for position of levers
[Image: 71-73_ac_heater_control.jpg]
--------------
Make sure your octopus is in good shape and the rubber isn't falling apart.
The problem is the colors fad over time. Example Purple can be faded to white.

--------------

Black is the main vacuum line from the Vacuum canister in the engine bay.
This is the main feed for all vacuum motors. The Vacuum canister is mounted on the
passenger side of the engine bay apron. It acts as Vacuum storage. The climate control system is
one giant vacuum leak so the vacuum canister helps stabilize the system.
It has a larger input vacuum line, that comes from full manifold vacuum, and the outlet
is a smaller line that goes into the Cabin through the firewall.


you will notice on the firewall there are 2 vacuum lines one going into the cabin and a second going to the
coolant Bypass valve on the Heater core feeds coming off the water pump on the engine.
----------------


Blue controls the center vents/defroster vents deflector.
when you set the system off Hi/lo vent, this motor activates, closes the door that
feeds the center dash vents and drivers and passenger side vents, sending all upper air in the system to the
defroster under the windshield

view of the blue motor
[Image: 100_1071.jpg]

-----------------

Red/yellow controls the floor vent and sends air to the upper vents. red is the bottom connection, yellow top/side.
this is the only double vacuum motor and its attached to the center fan blower unit.
this vacuum motor is used when you adjust how much air to send to the defroster or floor. as you adjust the control slider between floor and defrost this vacuum motor moves the flapper.

view of the red/yellow
[Image: 100_1068.jpg]


-----------------
White controls the fresh air intake, its only on when the A/C is set to max power, when the A/C control is set
to max(recycle cabin air) the arm comes down under vacuum and lifts the flapper door under the fresh air
intake from the cowl. this chokes off the fresh air and opens up the side door to allow internal cabin air to
go back through the system for additional heating or cooling, this motor is in the upper position all the time
letting fresh air in, until the upper selector lever is set all the way to the left A/C MAX.
view of the white vacuum motor
[Image: 100_1058.jpg]
view of valve
[Image: 100_1121.jpg]

---------------
purple controls the lower heater bypass, and is tied to the coolant bypass valve in the engine bay,

through a valve on the front of the heater box, behind the glove box.
[Image: 100_1120.jpg]

As you shift the lower A/C controls from Hot to Cold purple slowly chokes off the heater core allowing air to bypass
at the bottom of the main box once the A/C control lever is set fully to cold the cable arm hits the button
on the heater box valve which turns on vacuum to the coolant bypass valve in the engine compartment and shuts down
the heater core completely. As you move the hot/cold slider there is also a mechanically connection to a second upper flapper that again controls the amount of heat entering the system. when the system is fully cold, the upper door is closed the bottom door is open, the upper flapper arm makes contact with the valve and vacuum goes back out to the engine bay to turn off coolant to the heater core.

complete view of Purple system
[Image: 100_1118.jpg]

the octopus is in the lower right, feeds up the right side into the vacuum motor, it splits to the left center of
picture and feeds the white valve, that is turned on when the arm hits the button on it. which then turns on the vacuum line
out to the engine bay and shuts down the coolant valve to the heater core.


--------------
now there is an electrical switch for the A/C compressor which is only turned on when the lower selector is set
to full cold. this is part of the main A/C controls at the bottom of the center dash.

so its possible to set the upper lever to A/C MAX, and the lower lever off COOL and have the system recycle
cabin air and heat it again without the A/C compressor on.


there is also a temperature sensor that runs through the evaporator to prevent the evaporator from icing up and
overloading the A/C compressor.
[Image: 100_1142.jpg]



there is also a mechanical pressure valve that both a/c lines go through in the engine bay it usually has
an orange cap on it. this prevents damage from over pressurizing the system.



What things look like installed in the dash
here you can see the Purple lines and the white line above.
[Image: 100_1182.jpg]

connections to the temperature sensor for the evaporator core.
[Image: 100_1181.jpg]

blue line feed on the center fan unit. you can also see the black line main feed and the purple line going out to
the coolant bypass valve
[Image: 100_1196.jpg]

view of the red line
[Image: 100_1197.jpg]

view of the octopus
[Image: 100_1206.jpg]

complete system laid out on floor.
[Image: 100_1220.jpg]

  Reply
#4
72HCODE;21272 Wrote:OK, my internet is Slow and craptacular today.

Here is my write up.
-------------------
Link to my photos of rebuilding a heater A/C box
http://s1031.photobucket.com/albums/y377/72hcode/Heater Box AC/
----------------
Reference this for position of levers
[Image: 71-73_ac_heater_control.jpg]
--------------
Make sure your octopus is in good shape and the rubber isn't falling apart.
The problem is the colors fad over time. Example Purple can be faded to white.

--------------

Black is the main vacuum line from the Vacuum canister in the engine bay.
This is the main feed for all vacuum motors. The Vacuum canister is mounted on the
passenger side of the engine bay apron. It acts as Vacuum storage. The climate control system is
one giant vacuum leak so the vacuum canister helps stabilize the system.
It has a larger input vacuum line, that comes from full manifold vacuum, and the outlet
is a smaller line that goes into the Cabin through the firewall.


you will notice on the firewall there are 2 vacuum lines one going into the cabin and a second going to the
coolant Bypass valve on the Heater core feeds coming off the water pump on the engine.
----------------


Blue controls the center vents/defroster vents deflector.
when you set the system off Hi/lo vent, this motor activates, closes the door that
feeds the center dash vents and drivers and passenger side vents, sending all upper air in the system to the
defroster under the windshield

view of the blue motor
[Image: 100_1071.jpg]

-----------------

Red/yellow controls the floor vent and sends air to the upper vents. red is the bottom connection, yellow top/side.
this is the only double vacuum motor and its attached to the center fan blower unit.
this vacuum motor is used when you adjust how much air to send to the defroster or floor. as you adjust the control slider between floor and defrost this vacuum motor moves the flapper.

view of the red/yellow
[Image: 100_1068.jpg]


-----------------
White controls the fresh air intake, its only on when the A/C is set to max power, when the A/C control is set
to max(recycle cabin air) the arm comes down under vacuum and lifts the flapper door under the fresh air
intake from the cowl. this chokes off the fresh air and opens up the side door to allow internal cabin air to
go back through the system for additional heating or cooling, this motor is in the upper position all the time
letting fresh air in, until the upper selector lever is set all the way to the left A/C MAX.
view of the white vacuum motor
[Image: 100_1058.jpg]
view of valve
[Image: 100_1121.jpg]

---------------
purple controls the lower heater bypass, and is tied to the coolant bypass valve in the engine bay,

through a valve on the front of the heater box, behind the glove box.
[Image: 100_1120.jpg]

As you shift the lower A/C controls from Hot to Cold purple slowly chokes off the heater core allowing air to bypass
at the bottom of the main box once the A/C control lever is set fully to cold the cable arm hits the button
on the heater box valve which turns on vacuum to the coolant bypass valve in the engine compartment and shuts down
the heater core completely. As you move the hot/cold slider there is also a mechanically connection to a second upper flapper that again controls the amount of heat entering the system. when the system is fully cold, the upper door is closed the bottom door is open, the upper flapper arm makes contact with the valve and vacuum goes back out to the engine bay to turn off coolant to the heater core.

complete view of Purple system
[Image: 100_1118.jpg]

the octopus is in the lower right, feeds up the right side into the vacuum motor, it splits to the left center of
picture and feeds the white valve, that is turned on when the arm hits the button on it. which then turns on the vacuum line
out to the engine bay and shuts down the coolant valve to the heater core.


--------------
now there is an electrical switch for the A/C compressor which is only turned on when the lower selector is set
to full cold. this is part of the main A/C controls at the bottom of the center dash.

so its possible to set the upper lever to A/C MAX, and the lower lever off COOL and have the system recycle
cabin air and heat it again without the A/C compressor on.


there is also a temperature sensor that runs through the evaporator to prevent the evaporator from icing up and
overloading the A/C compressor.
[Image: 100_1142.jpg]



there is also a mechanical pressure valve that both a/c lines go through in the engine bay it usually has
an orange cap on it. this prevents damage from over pressurizing the system.



What things look like installed in the dash
here you can see the Purple lines and the white line above.
[Image: 100_1182.jpg]

connections to the temperature sensor for the evaporator core.
[Image: 100_1181.jpg]

blue line feed on the center fan unit. you can also see the black line main feed and the purple line going out to
the coolant bypass valve
[Image: 100_1196.jpg]

view of the red line
[Image: 100_1197.jpg]

view of the octopus
[Image: 100_1206.jpg]

complete system laid out on floor.
[Image: 100_1220.jpg]

Thanks...That is great! I knew someone new about this mystery. I have an AC box with no ac. The car had it originally. I am going to keep all the vac sensors in place and hook all of them up in case I want ac some day. I have all the original parts for the ac. Will the box work properly? I just need heat (defrost and lower vent).

You stated "you will notice on the firewall there are 2 vacuum lines one going into the cabin and a second going to the
coolant Bypass valve on the Heater core feeds coming off the water pump on the engine". Where is this second feed going to the bypass valve on the heater originate? My car had the heat disconnected and I don't see or recall any lines going to a valve. I do remember a small device located in one of the hoses at the heater core feed or return line but there was no line to it. I guess there should be a vac line to this part. I will check it out. I am in the process of rebuilding the heater box and am starting to think about reinstalling after the cowl repair which is going at a snails pace...lol.

Can I test the system w/o engine installed?

I also think I have a resistor issue in the box. The hi runs with a direct 12V feed but the med and lo doesn't work. Don from Ohio Mustang sent me a used one but I haven't had a chance to install it. The blower is in the car but the box is out.

I will have more questions when I get into this if you don't mind.

One more thing...is there any electrical switches or gadgets that I have to worry about for the heat aspect of the car besides the obvious switch with the 12V feed? Is it all on vac?

Thanks Again,
D. Rolls

Chasing Rust
  Reply
#5
The coolant cutoff valve goes on one hose from the water pump to the heater core.

The vac line for it runs into the cabin and connects to the purple system line.


You can use a hand vacuum pump hooked up to each individual vacuum motor to test them or hook the pump to the black line and test the system as a whole.


Nothing electrical to worry about other then the fan, the coolant goes into the heater core and the fan blows the air over it , with the vac motors not working all the air will flow out the center and side vents , your defrost won't work I believe and the cold to hot lever will have no effect, that's just if you hook up the heater and the fan, with no vacuum motors working.


On the side of the fan unit accessed from the drivers foot well next to the accelerator pedal you will see a red panel with 2 hex head screws, the electrical connects for the fan speed control there, when you open the red panel you will see a coil of wire, this controls the 2 speeds low and med, if something is wrong that's one spot to check.

The other can be the main switch in the climate control panel, it can burn out, or the connector melt, finding a replacement switch used to be really hard, check with don if you trace it back to a bad switch.

The reproduction fan motors for the a/c system are garbage try to stick with the original if possible.
  Reply
#6
Wow! That is a great write up!

[Image: 386_07_10_13_5_58_42.jpeg]
My Mustangs:
71 M-code Mach 1, Medium Blue/White Sport, 4R70W, 3L50, Factory Ram Air.
72 Q-code Mach 1, Pewter/Black Sport, 4-spd, 3L25.
73 F-code Convertible, Planned: color TBD/Black top/White Int., 351C, 5-spd, 3L50.
65 Convertible, Britney Blue/White/White, more modified than original.
05 Convertible, Legend Lime/Tan/Tan, future classic??
  Reply
#7
72HCODE;21335 Wrote:The coolant cutoff valve goes on one hose from the water pump to the heater core.

The vac line for it runs into the cabin and connects to the purple system line.


You can use a hand vacuum pump hooked up to each individual vacuum motor to test them or hook the pump to the black line and test the system as a whole.


Nothing electrical to worry about other then the fan, the coolant goes into the heater core and the fan blows the air over it , with the vac motors not working all the air will flow out the center and side vents , your defrost won't work I believe and the cold to hot lever will have no effect, that's just if you hook up the heater and the fan, with no vacuum motors working.


On the side of the fan unit accessed from the drivers foot well next to the accelerator pedal you will see a red panel with 2 hex head screws, the electrical connects for the fan speed control there, when you open the red panel you will see a coil of wire, this controls the 2 speeds low and med, if something is wrong that's one spot to check.

The other can be the main switch in the climate control panel, it can burn out, or the connector melt, finding a replacement switch used to be really hard, check with don if you trace it back to a bad switch.

The reproduction fan motors for the a/c system are garbage try to stick with the original if possible.

Hey Thanks... I will post a few pics with questions. I have the vac canister which was mounted on the passenger side back apron. I don't think I have the vac valve on the hose. There is a vac valve but it has two connectors. I thought it was a heat sensor for the emissions when it had it many moons ago. I'll grab a pic.

Chasing Rust
  Reply
#8
I think later mustangs 73 did have an electrical connection to a silenoid on the carb throttle arm, that bumped up the idle Rpms when the ac was turned on.
  Reply
#9
Here is a pic of the two items. The vac can and what I think is emissions heat sensor? No heater valve


Attached Files Thumbnail(s)
   

Chasing Rust
  Reply
#10
Yes that is the vapor canister for the fuel tank vent.

The other Looks like somebody hacked in a Distributor vacuum control valve

That valve is suppose to go on the water pump. And hook up to ported vacuum and full manifold vacuum, when the car over heats the valve opens and switchs the vacuum advance on the distributor to run off manifold vacuum which raises idle Rpms which in turn raises fan cooling Rpms.

See this for reference.
http://www.mustangsunlimited.com/itemdy0...=DY165A+01

This is the correct valve you need.
http://www.mustangsunlimited.com/itemdy0...1=YG136+01


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