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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

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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.

 

 

 

 

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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

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

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

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

100_1058.jpg

view of valve

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.

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

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.

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.

100_1182.jpg

 

connections to the temperature sensor for the evaporator core.

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

100_1196.jpg

 

view of the red line

100_1197.jpg

 

view of the octopus

100_1206.jpg

 

complete system laid out on floor.

100_1220.jpg

 

 

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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

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

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

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

100_1058.jpg

view of valve

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.

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

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.

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.

100_1182.jpg

 

connections to the temperature sensor for the evaporator core.

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

100_1196.jpg

 

view of the red line

100_1197.jpg

 

view of the octopus

100_1206.jpg

 

complete system laid out on floor.

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

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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.

 

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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

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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.

 

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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/itemdy00.asp?T1=DY165A+01

 

This is the correct valve you need.

http://www.mustangsunlimited.com/itemdy00.asp?T1=YG136+01

 

 

 

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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/itemdy00.asp?T1=DY165A+01

 

This is the correct valve you need.

http://www.mustangsunlimited.com/itemdy00.asp?T1=YG136+01

 

 

 

 

If I am not hooking up the ac, do I need the heater valve or not. I think its for the ac function?

Chasing Rust

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you need some kind of valve on the heater core hoses, because during the summer you will need to choke off them.

 

if you have no valve there at all the system will just keep pumping engine heat into the cabin.

 

the best would be restoring the correct valve because then you can control the heat.

 

another option is to install a cut off valve that you turn on and off manually, this way at least you will get fresh outside temperature air without heating it.

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you need some kind of valve on the heater core hoses, because during the summer you will need to choke off them.

 

if you have no valve there at all the system will just keep pumping engine heat into the cabin.

 

the best would be restoring the correct valve because then you can control the heat.

 

another option is to install a cut off valve that you turn on and off manually, this way at least you will get fresh outside temperature air without heating it.

 

Thanks for the help. I will definitely need one. Got a vacuum pump from work and will feed 12V to the heater switch and test all the functions. Hopefully I'll have success. I still haven't figured out why the medium and low blower functions aren't working. Pulled the resistor and checked...looks fine, its not broken. Thanks again!

Chasing Rust

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you need some kind of valve on the heater core hoses, because during the summer you will need to choke off them.

 

if you have no valve there at all the system will just keep pumping engine heat into the cabin.

 

the best would be restoring the correct valve because then you can control the heat.

 

another option is to install a cut off valve that you turn on and off manually, this way at least you will get fresh outside temperature air without heating it.

 

Thanks for the help. I will definitely need one. Got a vacuum pump from work and will feed 12V to the heater switch and test all the functions. Hopefully I'll have success. I still haven't figured out why the medium and low blower functions aren't working. Pulled the resistor and checked...looks fine, its not broken. Thanks again!

 

Just finished rebuilding my heater box. Tested vac modules with a vac pump. Everything seems to be working well.

2011-05-07_09-18-01_668.thumb.jpg.1635118351236aad56f61d572b90467e.jpg

Chasing Rust

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Wow - looks great. Nice work!

Doc

Project started 8-7-10

Completed: All new suspension, rebuilt 351C H Code bored .030 over with mild cam and intake, new 3.50 TracLok, custom exhaust system

Current "mini-project": interior upgrade :-/

[button=http://www.7173mustangs.com/forum-garage?filterxt_uid=76]Doc's Garage[/button][button=http://www.7173mustangs.com/thread-1973-mustang-convertible-restoration-and-modification]Doc's Wiki[/button]

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Your cowl foam seal looks too thin, you may need to build it up, but wait till install and adjust as needed.

 

 

Looking good so far

 

As for the fan, might be the switch is bad.

 

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Your cowl foam seal looks too thin, you may need to build it up, but wait till install and adjust as needed.

 

 

Looking good so far

 

As for the fan, might be the switch is bad.

 

 

Thanks guys!

 

I haven't actually fastened my fabbed ring with the hat seal. I definitely will be gluing a piece on to raise it. I want to wait until I mock fit it and locate the ring in the right place. Good catch!

 


Wow - looks great. Nice work!

 

I am trying...Thanks!

Chasing Rust

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  • 1 year later...
  • 3 months later...

 

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

 

That valve is suppose to go on the water pump.

 

Actually, that is incorrect. The 351C has the "H" pipe in the heater hose lines with the ported vacuum switch for emissions control as well as the one on the water pump. I have the exact same arrangement on both of my 351C powered '73's. The "H" pipes rot out and aren't available.

 

If you look at the factory vacuum diagram, it has 2 - ported vacuum switches. The one on the water pump is 3 ports (number 1 on diagram), the one in the heater hose "H" pipe is 2 port (number 2 on diagram).

Here's the diagram:

73%203-14A.jpg

tcvv.jpegdvcv.jpeg

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  • 2 years later...

Hey dudes...this is a great thread, but i cannot seem to find the answer to my problem

My problem: I have hot and cold air coming only through my windshield vent/defrost, i can adjust the fan speed and the temperature and they work fine but when i move the vent switch the air doesnt come out anywhere else. Is this an electrical problem or mechanical.

 

Thanks

'71

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Wally95:

 

default mode for the A/C box when there is a problem is the air just blows out the defroster.

the problem you have is vacuum related or mechanical, most likely vacuum.

 

the climate control system has a rubber manifold on the back side with numerous hoses coming out of it. We call this manifold the octopus because it kind of looks like one when you take it out.

 

vacuum comes from the engine bay. Full manifold vacuum from the intake manifold goes to the vacuum canister on the passenger side of the engine bay.

a hose from the canister then goes into the cabin of the car through the firewall.

 

that is the main vacuum line that feeds into the octopus and through that all the vacuum motors function when selected.

 

many times something falls apart in the system and gets blown into the control system which clogs up the mechanical.

 

you can try using a hand vacuum pump to test all the vacuum motors one at a time and make sure they work and do not leak. this will move all the flappers internally and make sure there are no mechanical problems.

 

if the motors and flappers all function then the issue is inside the controls where the levers/sliders are. you will most likely need to remove that control panel and try to blow out the clog, sometimes you cannot and the control panel will need to be replaced.

 

there are other issues that should be looked at the same time. the vacuum canister should be tested there is a reed valve inside that must only allow vacuum to flow one way. you can test the reed valve by blowing and sucking air into and out of the canister if air only moves one way then the reed valve is good if you can move air both ways then the canister must be replaced.

 

the heater core control valve should be inspected and tested for operation, they rot out over time and need to be replaced every couple of years.

 

 

so test the motors one at a time using a hand pump. make sure everything is free and working without leaks. then take apart the control panel and remove the octopus blow everything out with compressed air, inspect for cracked dry rotted rubber hoses and replace as needed.

blow out the controls and you can try hand testing the manifold with the hand pump. the hoses are color coded. Black is the vacuum input.

http://s1031.photobucket.com/user/72hcode/library/Heater%20Box%20AC?sort=2&page=1

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