AC install confusion

[Eric McClellan]

Ok... First details, then question....


- Running standard VA slimline unit.
- Installed LS electric heater valve.

Question(s)....

I'm assuming I can eliminate this switch because I'm no longer using the VA vacuum heater valve, correct? (Figure I did, but wanted to verify before ripping into stuff. I would still use the one on the left as fan speed control.

I would then use this one (blue wire goes to trinary switch, yes? This also needs to be grounded, correct?) when I want AC.

And then use this one from the electric valve when I want heat.

So it would be a 3 switch system.
- Fan control
- Heat
- AC

Does this make sense? Has anyone done this? Seems pretty basic/easy to wire up make happen.

Do I have this right?

Thanks everyone.

 

[Will Campbell]

Yes, mine is done that way: fan speed, heater control valve, and AC.

 

[Ken Roberts]

Here is my take on it although mine is not running yet.

Picture #1
-you need the rotary switch on the left to control the fan speed.
-you can eliminate the rotary switch on the right but you must replace it with a simple toggle switch. This switch is a on/off for the A/C. This switch would then send current to the A/C thermostat rotary switch in picture #2

Picture #2
- the rotary A/C thermostat is a normally closed switch that simply opens if the thermocouple detects a freezing condition at the evaporator. The blue wire connects to the binary or trinary switch. The bi/trinary switch is also a normally closed switch that will open if excess pressure is detected. The bi/trinary switch is then wired to the A/C compressor.

Picture #3
-this rotary switch controls the coolant flow to the heater core. It is used to control the heat output in conjunction with the fan speed switch.

 

[Ken Roberts]

The right rotary switch in picture #1 is confusing to many builders. The "mini slimline" doesn't have a econo position, heat position or defrost position. This switch acts as a simple A/C on or A/C off switch only. If you eliminate it you must have a new way of turning the A/C on and off. Turning the A/C on and off is equal to sending current to the A/C compressor or not. Current sent to the compressor is A/C "on". Shutting off the A/C is done by stopping the current flow to the compressor.

In conclusion.......if you elect to eliminate the rotary switch on the right in picture #1 and just join the two wires together behind the switch then your A/C will be on all the time. It must be replaced with a toggle switch if eliminated.

I would recommend removing it because of it's confusion. In it's place you could install the rotary switch in picture #3. Then mount a simple on/off switch near by for the A/C.

 

[Eric McClellan]

Thanks Ken for the clarification.

Which wires would be the ones needed to turn the ac on or off?

I'd like to have a rotary switch to make the knobs all be the same.

I guess I'm also still confused by the AC thermostat switch... Does this control how cold the air is?

 

[Alex]

a/c......lol

heater ...... lol

 

[Ken Roberts]

Explanation of the A/C thermostat is on page 9 here Eric. http://www.vintageair.com/AC Basics/acbasics51412.pdf

Basically the A/C thermostat has a capillary tube that measures the temps at the evap coil. It's job is to prevent the coils from freezing up. Your job is to set the knob as far clockwise as you can without having the coils freeze. The farther clockwise you turn the knob the colder the output. All it's doing is opening and closing (cycling) how often the compressor runs.

The wires needed to turn A/C on and off are the same 2 wires that are currently connected to the back of the rotary switch on the right side.

If you want three rotary switches that match then use them "as is" or buy a separate rotary switch that only has one position....simply on and off. That's what I plan to do. You could then buy three custom knobs and mount them on a custom plate.

 

[Eric McClellan]

Thanks Ken.

Wouldn't I have 4 rotary switches total? 3 from the VA system (AC level, AC on/off and fan) and 1 from the heater control valve?

I guess I'm just trying to figure out how it 'turns on'. I only seen one wire (white and black) to the trinary switch that would trigger the AC system.

Incidentally, I assume the one black wire off the AC compressor is the trigger wire? The VA system comes with a ground strap for the compressor, but isn't it self grounding since it's touching the motor in 3 places?

Maybe I'm over thinking this.

 

[Ken Roberts]

Yes....sorry that would be 4 switches.

The ground strap is just extra insurance I suppose.

See page 7 for the trinary switch wiring. http://www.vintageair.com/AC%20Basics/acbasics51412.pdf

You only need to use a trinary switch if you want the rad fan to come on during A/C operation. Otherwise a binary switch is simpler.

Here is a video on using the trinary switch. https://www.youtube.com/watch?v=l604JCZx_ow#t=185

 

[Eric McClellan]

Dumb question, but how does the Isis system tell the ac system to turn on? Is that from that white and black wire?

 

[Aaron H.]

Eric:

I'll sell you a copy of my wiring diagram? It's in color, completely labeled and available in AutoCAD or pdf format.

 

[Aaron H.]

Grounding the white/blk wire to the ISIS master cell signals the ISIS system to turn in the A/C compressor.

NOTE: This wire probably has an ISIS invert so you actually supply 12 VDC to it and then the invert grounds the white/blk wire.

 

[Eric McClellan]

RCR SLC AC Vintage Air slimline wiring: http://youtu.be/pRrJIpKwofU

 

[Aaron H.]

Eric:

In your video, your trinary switch looks like it will interfere with the body when you install it. You may want to check that..

 

[Eric McClellan]

Eric:

In your video, your trinary switch looks like it will interfere with the body when you install it. You may want to check that..

You're right.

It does move a little bit up and down. I'll have to see how it goes when I drop the body down.