ATC workaround

[thethee]

Okay guys, I have decided that I'm going to work on my ATC system and thought it would be best to start a thread for questions along the way.

My plan is to convert the system to a manual or as much as possible, I'll see how far I'll come.

Before anyone tries to discourage me, right now the ATC is dead, I only have a blower that can be pointed at the defrost outlet and the dash outlet. So basically it can't be any worse and any improvement is a bonus. I'm pretty sure the A/C has lost all refrigerant and I doubt there is still any oil in the RV2 compressor, but it's not seized. I have disconnected it just to be safe. The manual controls were installed when I got the car. After searching the internet and studying the FSM I concluded that I should be able to create a workaround with the ATC box.

First step, the water valve in the engine compartment, or better yet lack thereof. The original valve would have a cold engine lockout switch but for manual a simple vacuum closing water valve would suffice. I'm looking at this one, anyone have any experience with it?

 

[CBODY67]

There are many water valves of that sort around. Some have the vac chamber on top of the valve, others don't. When I went to one with the smaller chamber on my '70 Monaco (normal a/c), rather than the normal Chrysler-OEM style with the larger vacuum chamber, at certain vacuum levels, I noticed that I started to get a humming from the instrument panel "HEAT" lever. Apparently, the heat is controlled by a small variable vacuum bleed situation at the switch, so there are some sympathetic resonances in the engine's vac level/pulsations which affect it. I suspect that using an inline vac reservoir would cure it (or an OEM-style large-chamber/two heater hose connections water valve), but just learned to laugh when it happened, or at least smile, and then adjust the throttle to decrease the sound.

Personally, I suspect you can have success in your venture as it can be just a different way of operating the hardware that's already there.

Keep us posted,
CBODY67

 

[70NEWYORKER]

That water valve you posted will not be good for making finite adjustments to heater output. Those small vacuum chamber valves work more as an ON/OFF switch.

 

[bigmoparjeff]

The 1974-78 C bodies use a blend door inside the HVAC box to control temperature. The water valve is fully closed when the system is OFF or in the MAX A/C position, and fully open in all other modes. The factory service manual doesn't specify if applying vacuum closes or opens the valve, but the majority of the time vacuum will be used to close these valves. As long as the valve from Rock Auto does the same thing as the original when vacuum is applied, it should work fine.


Jeff

 

[thethee]

The FSM doesn't state it directly but I figured from the vacuum schematics of the manual A/C that vacuum closes the valve so this valve should be correct. Should be here next week.

After that, time to pull the dash!

 

[bigmoparjeff]

You did a better job of studying the diagram than I did. I missed the water valve on there.

You don't actually "pull the dash" on a formal, as the dash frame is welded to the body. You should have good access to most of what you need to get to by removing the dash pad, which is pretty easy. In most respects, dash related work is much easier on a formal than the earlier cars. I pulled the entire ATC vacuum harness out of our '78 NYB way back when I was 17 or 18 years old, and I don't remember having any difficulties getting to anything once the pad was off.

Jeff

 

[thethee]

Yeah that's what I meant

 

[300rag]

...

You should have good access to most of what you need to get to by removing the dash pad, which is pretty easy. In most respects, dash related work is much easier on a formal than the earlier cars. I pulled the entire ATC vacuum harness out of our '78 NYB way back when I was 17 or 18 years old, and I don't remember having any difficulties getting to anything once the pad was off.

Jeff

Someone should have told @commando1 that.

 

[commando1]

Someone should have told @commando1 that.

His memory is clouded. My memory is still fresh.

 

[1978 NYB]

 

[1978 NYB]

 

[thethee]

View attachment 443289

Looks good!

In Dutch we have a saying "vaak ben je te bang" which translates to "often, you're just too scared"

 

[75LandYacht]

I’m very interested in your thread, eager to see your progress, as my 77 ATCll system is InOp as well.. keep us posted.

 

[thethee]

Decided to look through the wiring diagrams today. Right now the blower motor switch has 4 settings, off-low-medium-high. According to FSM this should have 4 settings, low-M1-M2-high, and off is controlled by vacuum push button "off". Something to check for when the dashpad comes out, probably a PO wiring attempt cause I don't think only one resistor can go bad. Then the blower motor wouldn't work at all right?

Also, in the manual A/C part of the wiring diagram for some reason they show two switches and resistor blocks, but in reality this is just the same switch and resistor block for both A/C and heat right? Can anyone with a manual A/C confirm?

 

[bigmoparjeff]

Yes there's only one switch and resistor block per car.

Jeff

 

[3C's & a D?]

That water valve you posted will not be good for making finite adjustments to heater output. Those small vacuum chamber valves work more as an ON/OFF switch.

The same is true of all manual systems, hot water is either all the way on, or off. Infinite adjustment is available using the blend door.

 

[70NEWYORKER]

The same is true of all manual systems, hot water is either all the way on, or off. Infinite adjustment is available using the blend door.

My Chrysler has the manual system and the heat is quite adjustable with the water valve. There is NO blend air door. The water valve also has a vacuum pot ten times the size of the one I mentioned earlier in this thread.

 

[3C's & a D?]

My Chrysler has the manual system and the heat is quite adjustable with the water valve. There is NO blend air door. The water valve also has a vacuum pot ten times the size of the one I mentioned earlier in this thread.

My apologies, The manual vacuum operated systems I'm familiar with, mostly '71's, with the larger, stock vacuum pot, were equipped with a blend door. Cable operated, non A/C systems can be adjusted with small increments of the lever. However also have a blend door.

Your 1970 Chrysler with manual A/C has no blend door/lever?

 

[70NEWYORKER]

Your 1970 Chrysler with manual A/C has no blend door/lever?

Nope. Temp is regulated by throttling water flow thru the core. All HVAC air passes thru evaporator and then heater core.

 

[3C's & a D?]

Nope. Temp is regulated by throttling water flow thru the core. All HVAC air passes thru evaporator and then heater core.

Interesting, thanks for correcting me on that. That seems like an odd way of doing things. All vacuum pots are essentially on /off switches, I would think the throttling would depend on what the controls in the car are calling for, although, I was wrong before. On that note, how do you adjust the temperature in your car, is it a sliding hot/cold lever? Any pictures? All I could find was autotemp pictures.

The manual controls were installed when I got the car.

Can you post a picture of the manual controls in your car? Is there a blend door control, and a blend door on the HVAC box?

I also recall there being a member here around three years ago that created a thread on converting ATC to manual, I can't remember what year of car.