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youracauthority.com/acterms/Pilot_Operated_Absolute_POA_Valve.shtml


"The POA valve was used on some General Motors and Ford air conditioning systems through the 1970�s. On these A/C systems, the compressor would run constantly whenever the A/C system was on. Under certain operating conditions, less compressor suction was required on the evaporator. The POA valve would then close off the flow of refrigerant, effectively reducing the amount of compressor suction."



youracauthority.com/acterms/Suction_Throttling_Valve_STV_Valve.shtml

"Typically used on older A/C system designs, the STV valve has been replaced because of fixed orifice tubes and cycling compressors."


So, take out cycling compressor, add STV of POA valve it would seem. I feel i'm on the right track, especially after being only a couple hours into research.

If the Sanden Compressor clutch requires 7.5 volts with a max of 49 watts, then that is a max of 6.5 amps. With 12 volts at 49 watts, thats 4 amps max.

So why not get a 6 > 12v voltage step-up converter that is rated to handle that amperage with a constant load.

I know they sell those step-up convertors to run 12v radios in 6v cars and most radios with internal amplifiers pull between 5 and 10 amps constant. So it may be a good fit.

Just floating an idea.

POA valves were used on lots of cars and provide a constant temp for the evaporator. Believe they are rather sensitive to size of evaporator and also have some plumbing requirements so the oil can route around and not get trapped so a little more complex and some engineering required. Suction throttling is a little less involved as is basically a pressure differential balancing act between evaporator, atmosphere and springs. HGB the simplest as valve just opens or closes but the trick is to ensure liquid refrigerant is not able to get to suction side and damage compressor. 53-4 Packard was an electric solenoid valve mounted on fender to right of compressor and 55-6 was a modulator valve similar to expansion valve and was mounted at exit of evaporator at firewall. There was an extra run of tubing on both to short circuit the freon. Don't know how the Buick system was plumbed. Cadillac also used the solenoid while Ford products used a modulator. Here is a brief description of how HGB worked.


EDIT: Regarding Kevs post on the inverter/converter. A good idea but make sure to find one rated for inductive loads such as motors. The only one I've seen that is a possibility is by Newport engineering which they list as an accessory for their wiper motors. Again, that is even iffy because it's fused for 5 amps. Most inverters I've found absolutely state not for use with motors ie inductive loads.

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That was of course my first step, but most research turns up threads that say you can't use one with AC because the load is too much. Since i'll probably be using an A6 or similar compressor for looks and price, that means i'll have to have one closer to probably 10 volts for minimum ( i don't know what the minimum closing voltage is for an older compressor, assuming)

Now if i could find a step up converter to do that to do that, that'd honestly be the best of all worlds. AC with an on and off clutch that cycles itself as needed (and probably VIR based instead of 60's muscle style which are parts i've been reading about). However, the only step ups i've found so far are in the 800mh to 1 amp range. I'm sure a heavier one could be custom built and you could honestly sell the crap out of those to lazy 6v people like myself who don't want to convert. I'm still going to look tonight and see if i can find a heavier duty one, even if it had to hide under the dash or somewhere similar and run 12v out to the compressor.


From what i've read (which i could have interpreted wrong), even clutch enabled compressors up until somewhere in the 70's ran all the time that the AC was on. If it was off the clutch was off and if you turned it on the clutch was on. They didn't seem to cycle automatically and used STV valves or POA valves.

From what i understand the VIR (valve in receiver) setup has a pressure/temp switch that cycles the compressor, and that came out late 70's.


If all that is correct, and you had, say a 71 tempest to look at (i do!) and you ran the ac most of the summer, and had a packard with constant on compressor that you drove only really in the summer, you could expect the same kind of AC performance and reliability/AC component life (in the ballpark anyways.)


So unless i can find a really good step up converter, i still think best bet is to mimick a 60's air system that has the AC switch turned on all the time (for my driving habits, no saying this works for all).

Also, lets not forget a movable compressor mount with lever operated through linkage that lets you tighten the belt against the compressor to turn on or relax it slightly to let it slip

Ok, lets forget that, it belongs on a tractor, not a fine car like the packard.

After searching from a radio point of view as Kevin suggested, i turned up a two amp model and a 5 amp model so far. This would be good news, as i believe looking at a step up is usually a dead end when discussing 6v AC installations. I'll see if i can get closer to a 10 amp, which i would be comfortable with buying to try.

I have to admit I know nothing about this topic, but what about one of those batteries that are 12v with 6v output? The 12v would run the AC and the 6v everything else. Otherwise, could you add another 6v generator and tie the two together to create a 12v source, or doesn't it work that way?

I think you could run two generators with separate circuits and add them together, but that'd be a lot of physical limitation on engine space when added to the compressor.

The 12v system with 6v post battery would work, but you gotta charge it. Maybe a low amperage step up would work for that? 12v and 6v combination battery with 12v going only to compressor clutch and then the step up 12v wire across the two positive posts? That's an interesting theory to consider. You'd have a decent amount of 12v power storage in the battery, and with 12v compressor you could use an autocycle on and off system to save the power you do have while it charges.






51Packard wrote:
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The battery is the best idea for the current needed. Here is what you are going to find with most any inverter (at least the ones I've found so far) Note the disclaimer.powerstream.com/dc6-12.htm

If you did the cycling clutch rather than constant on, then just about any aftermarket unit--even time period appearance hang ons such as those sold by Vintage or Classic air would work nicely and be lots less work.

If you could find a 6v to 110v inverter then a battery tender type thing could be hooked up between the two to keep the extra battery charged.

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As far as constant on vs cycling, that seems to be more dependent on the parts you use behind the compressor (valve types, vir vs dryer and poa, etc) and you can hide most of that and both types seem readily available.

The cycling compressor type with the inverter you mentioned (which looks like one SERIOUS unit) would be the most electrically energy efficient and wouldn't require a combo battery, and would likely give the alternator a chance to charge the system in between cycles. The only down side is the $300 inverter price.

I fired off an email on the other one posted (5a) and asked if the higher rated 5a neg ground inverter could be used in a pos ground setup if it was isolated to prevent shorts. If so, i'd take a gamble on the one for $99 (i could use it for a radio in the packard glove box anyway) and test it with the compressor i have. The higher rated one, well, it'd have to be a good month at work to throw $375 at a test.

I guess the question I would have is if a motor clutch is same type of load as an electric motor itself. The Sanden specs claim to have a peak of 49watt at 7.5 volts = 6.5 amps. So if that was the case the inverted that Howard listed above would be overkill at 20amps.

I think the issue with actual electric motors is that they usually have a huge peak draw when starting up, then level off.