1965 AC Bypass Switch

[PocketAces]

I'm restoring my air conditioning and heater boxes and I have a mystery to solve.

I've located schematics for 66 and 67 AC and I understand the schematics pretty well.
View attachment 67 AC Schematic.jpg
They both show something called a "Air Conditioning and Heater Resistor Bypass Switch". The purpose seems to be increase the fan speed when set to Max AC. But these schematics do not show where this switch is physically located.

I have three different heater boxes from parts cars and one of them has a bypass switch which is tripped by the movement of the fresh air/recirculate door. It looks like this:
View attachment 20150317_093438_resized.jpg
The other two heater boxes do not have this switch. Unfortunately I don't remember which heater box came off my car.

I have a similar switch on my air conditioner plenum which is tripped by the movement of the door that controls whether air goes through the evaporator or down to the heater/defroster outlets. It looks like this:
View attachment 20150317_092744_resized.jpg

The 1965 Factory Service Manual I have does not cover factory air for Darts. I guess it was too new to make it into the manual.

The 1966 Factory Service Manual I downloaded contains the following passage:

BY-PASS Switch
The by-pass switch increases the blower speed
when the “Max A/C” or “Fresh Cool” button is pushed.
​

It also contains this table:
View attachment HVAC Push Button Control Chart.jpg

So based on the 66 FSM, I'd say the bypass switch should be the one on the heater box that is switched by the movement of the fresh air/recirculate doors shown in the first picture.

But I'm trying to understand the other switch shown in the second picture. I'm thinking perhaps the design changed in 1966 and that perhaps the earlier 1965 design had the switch in a different location. But if that were the case, the blower speed would be boosted any time the air conditioning is on, be it Max AC or AC. Does that make sense?

Does anybody have a 1965 with AC that could tell me where the bypass switch is located? I know that's a tall order since both switches are hard to see when the system is installed behind the dash.

Also does anyone know if there is a separate manual which covers 1965 A-Body Air Conditioning?

 

[PocketAces]

Reading further in the 1966 Factory Service Manual.

By-Pass Switch Adjustment
With vacuum applied to the rod side of the inlet
door actuator, the blower motor resistor by-pass
switch must be adjusted so that the vacuum actuator
shaft will engage the switch lever, with .020 to .060
inch clearance between the inlet door tang and the
switch base, moving the switch lever to the closed (on)
position with vacuum applied to the top of the
actuator.​

Now I'm more confused. I'm pretty sure that "Inlet Door" is the door that allows air to go through the evaporator when open. This door is open whether the controls are set to Max AC or regular AC. But that does not agree with the earlier text which implies that the bypass switch is only closed when the controls are set to Max AC.

Still need help with the questions from my earlier post.

 

[65dartcharger]

John! I have. 65 air conditioning book. I guess I could send it to you to use when assembling the a/c. I can shot some pictures from my convertible which has a factory a/c setup.

 

[PocketAces]

John! I have. 65 air conditioning book. I guess I could send it to you to use when assembling the a/c. I can shot some pictures from my convertible which has a factory a/c setup.

I'm not sure I need pictures. I think you could just check both locations and let me know where you find the bypass switch. I think it will either be on the top of the fiberglass heater box or on the metal AC box (behind the fiberglass box). In either case the two wires from the bypass switch will have a L-shaped plug that plugs onto the heater resistor.

No need to send me your book. Just take a look and see what you can find about the bypass switch.

 

[PocketAces]

I re-read the passages from the 1966 manual and I realize now that they are consistent with one-another.

BY-PASS Switch
The by-pass switch increases the blower speed
when the “Max A/C” or “Fresh Cool” button is pushed.
​

By-Pass Switch Adjustment
With vacuum applied to the rod side of the inlet
door actuator, the blower motor resistor by-pass
switch must be adjusted so that the vacuum actuator
shaft will engage the switch lever, with .020 to .060
inch clearance between the inlet door tang and the
switch base, moving the switch lever to the closed (on)
position with vacuum applied to the top of the
actuator.​

So at least in 1966, the bypass switch closes and the fan speed is increased any time the AC is on, Max or regular.

But the question remains, where did I get this heater box with a second bypass switch triggered by the fresh air and recirculate doors? Was the bypass switch moved between 1965 and 1966?

 

[65dartcharger]

I'm restoring my air conditioning and heater boxes and I have a mystery to solve.

I've located schematics for 66 and 67 AC and I understand the schematics pretty well.
View attachment 1714801191
They both show something called a "Air Conditioning and Heater Resistor Bypass Switch". The purpose seems to be increase the fan speed when set to Max AC. But these schematics do not show where this switch is physically located.

I have three different heater boxes from parts cars and one of them has a bypass switch which is tripped by the movement of the fresh air/recirculate door. It looks like this:
View attachment 1714801184
The other two heater boxes do not have this switch. Unfortunately I don't remember which heater box came off my car.

I have a similar switch on my air conditioner plenum which is tripped by the movement of the door that controls whether air goes through the evaporator or down to the heater/defroster outlets. It looks like this:
View attachment 1714801185

The 1965 Factory Service Manual I have does not cover factory air for Darts. I guess it was too new to make it into the manual.

The 1966 Factory Service Manual I downloaded contains the following passage:

BY-PASS Switch
The by-pass switch increases the blower speed
when the “Max A/C” or “Fresh Cool” button is pushed.
​

It also contains this table:
View attachment 1714801186

So based on the 66 FSM, I'd say the bypass switch should be the one on the heater box that is switched by the movement of the fresh air/recirculate doors shown in the first picture.

But I'm trying to understand the other switch shown in the second picture. I'm thinking perhaps the design changed in 1966 and that perhaps the earlier 1965 design had the switch in a different location. But if that were the case, the blower speed would be boosted any time the air conditioning is on, be it Max AC or AC. Does that make sense?

Does anybody have a 1965 with AC that could tell me where the bypass switch is located? I know that's a tall order since both switches are hard to see when the system is installed behind the dash.

Also does anyone know if there is a separate manual which covers 1965 A-Body Air Conditioning?

I checked on my Dart wagon w/273 and A/C and it has the same setup as Picture number 2. Same on the convertible. If you like John I can shot picture for you.

 

[66Dvert]

My 66 is getting Factory A/c installed. the box looks like the one in picture #2 it came from a 65 dart(best overall shape after cleanup). I also have another box that came from a 66 plymouth that has the same switch on top just like the other one. I do have a 67-8-9 (not the complete heater core section but the A/c section and can't remember the exact year other than it's a 7-8-or 9 not a 70's ) that does have the switch located in the other position like the picture #3 that you have shown. I was unable to use it(the 67-8-9 part) since it's a bit longer and interfered with my gas pedal position but was in much better shape.

also check your resistor for the correct connections. some have more connectors than others,My 67 box did not have 6 connections only 5 on the heater core section.

going in the 66 but it's a 65 box with 6 connections for control
View attachment -0561.jpg

top location near the fresh air box section
View attachment -0562.jpg
better view
View attachment DSCF4246.jpg
full length of heater core section from the 66 plymouth
View attachment DSCF4245.jpg

 

[PocketAces]

Thanks guys. Looks like I should use the switch on the top of the heater box since it was present on both of Ulf's 65's and also on 66Dvert's 65 box. The 66 manual is pretty clear that it's located on the AC box, but perhaps the cutover didn't happen right at the beginning of 66.