Has anyone ever given into the temptation to pitch the whole Chevy A/C system, mount an aftermarket 200-amp alternator in the place of the A/C pump, and run the roof A/C off a couple-kilowatt inverter?
I know you lose a lot of energy going from mechanical->electrical->mechanical, but it seems like it would be a lot simpler to maintain than two air conditioning systems.
I have an '81 euro nose with the 454, and my AC pump has _some_ pressure (no idea how much; I haven't hooked up a gauge yet) but the clutch was disassembled by the previous owner. I hate to mess with upgrading to R134 right now and if I keep it R12, if there isn't a leak... there will be some day and I'll have to address this question all over again. Your thoughts? Anybody with experience on this? Thanks a bunch!

- Daniel.

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Has anyone ever given into the temptation to pitch the whole Chevy A/C system, mount an aftermarket 200-amp alternator in the place of the A/C pump, and run the roof A/C off a couple-kilowatt inverter?

I've definitely thought about it. I currently just run my 7000 watt diesel generator and thereby power up both rooftop air units, but if I use an inverter I will likely add a dedicated AC unit in the driver's roof area which is just run off the inverter. This will eliminate any need to use a disconnect. I'll add some plugs for other devices to use this dedicated system too.

As far as size, here is an excellent blog describing the all important LRA rating:

Power Inverters and Air conditioners:

I get a lot of questions about running an air conditioner on a power inverter. The air conditioner is one of the hardest household appliances to run off of an inverter. The first thing to do when getting ready to run an air conditioner on an inverter is to get all of the specifications for the AC unit. The most important spec that you will need is the LRA rating. What this stands for is locked rotor amps. The LRA rating is what the AC unit will draw from the inverter while the compressor starts up. This is a very important spec when sizing an inverter for use with an AC unit. After you get this spec you will multiply it by the voltage and this will be the startup wattage needed by the inverter.

For example if your LRA is 60.6 amps if you multiply this by 115 you will get roughly 7000 watts at start-up.

The next thing to take into consideration for a AC unit is battery bank size. The best batteries that we have found that work well with inverters are the 6 volt golf cart or solar batteries. These are more cost effective and on average have higher amp hour ratings then the traditional group 27 12 volt deep cycle batteries. The 6 volt batteries will be connected in series. This will double the voltage to 12 and keep the amp hour rating the same. The inverter will see this as one big 12 volt battery. Your average 6 volt battery is 220 amp hour and sells for approx. 65.00. and your average deep cycle 12 volt battery group 27 is 115 amp hour and sells for 130.00. So if you get two of the 6 volt batteries it is twice the size at 12 volt s and you pay just about the same amount . If you want any kind of run time with a air conditioner it will require a large battery bank. I would have to say a minimum of 4 6 volt batteries wired in series to get longer then an hour. One of your best sources for the 6 volt batteries is a golf course. Reason for this is because the golf courses will really only use the battery for 6-9 months before getting rid of them.

Your next step in setting up a system for use with an AC unit is finding a sufficient recharge source for the batteries. You will want to have a minimum of a 150 amp alternator to recharge a system with a small AC. There are also many other options available such as solar, wind or hydro.

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Originally posted by noble97monarch:
I currently just run my 7000 watt diesel generator and thereby power up both rooftop air units,

Yeah, same with us, but we close off the bedroom and just run the front one. Actually, we tolerate dry heat and outside air pretty well, but the combination of heat and humidity forces us to close up and drive with AC.

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but if I use an inverter I will likely add a dedicated AC unit in the driver's roof area which is just run off the inverter.

Do you mean something like a Polar Cub? They draw a little over 1000 watts, which is around 77 amps from a 14 volt alternator. If you can keep it cool, a single Delco alternator could do that.

As far as the operation of a standard AC, our Honda 2000i operates either of the 13.5 roof airs, on Eco or non-Eco. They are OEM with no added hard start caps or anything. I haven't tried them on the 2.5k inverter yet, but if the Honda, with its 2000 watt max and steady output of 1600 watts, does it, the inverter might do the job.

Those larger alternators heat up when used hard. Things in a P30 doghouse get pretty crowded and hot. Lots of cooling air becomes necessary to prevent diode failure.

If I really wanted more engine charging power, I would use two dual-belt high output Delco alternators. One in the stock location and the other where the AC compressor used to be.

I still have not figured out a good cold air supply for the one on the right. It is right up against the cylinder head which makes a "hat" a challenge. I have even considered moving the heat-sensitive diodes and regulator to a remote location.

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Do you mean something like a Polar Cub?

Yes, like that (now that I looked it up and know what it is).

I'm not sure what size my roof airs are, but there are days when they struggle to keep up. All the more reason I wouldn't mind a third unit to throw a little "overkill" at it.

I hadn't thought of the alternator/heat issue. Definitely worth consideration. Another - you don't get somethin-fer-nuthin moment!

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Originally posted by noble97monarch:


I hadn't thought of the alternator/heat issue. Definitely worth consideration.

Well, with a DP, it should be a little easier to provide alternator cooling than the crowded hot doghouse of a gasser.

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but there are days when they struggle to keep up. All the more reason I wouldn't mind a third unit to throw a little "overkill" at it.

As mentioned, we close off the bedroom. Some folks also hang a curtain farther forward. Either at the rear of the living room or just behind the front roof air, so all of its output goes forward.

Using dash air, some hang a curtain just behind the cockpit.

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Originally posted by bill h:
[QUOTE]Originally posted by noble97monarch:

Using dash air, some hang a curtain just behind the cockpit.

Reminds me of my 1958 VW bus with tempered masonite and plexiglass screwed to the back of the bench so I could keep a little warmth.

Debating if I should say anything, but here goes. If you have an R12 system that still works, you can recharge with a number of products. I use a product from Envirosave and it works. Compatible with R12 and R12 oil.

That being said I will also say it is a mixture of propane and butane and is considered industrial. But no ozone depletion or green house (R134) gas effect. But it will burn. I really don't care as I already carry propane, diesel fuel and gasaline (generator). A few onces of hydrocarbon compond in the AC will not make a difference.

No expensive retrofit required.

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Originally posted by Gary Carter:
If you have an R12 system that still works.....

"Still works" is a relative term for a GM gasser. Cold air from the dash outlets does not impress a big RV very much.

In hot areas, many GM SUVs have a second AC unit to take care of the interior volume. My dash unit, fully-charged and working well, did not offer much cooling to our 30 footer. Previous GM Class As were the same. Our Class C was OK, as the cab could be curtained off.

And then, there are the radiator heat and air flow issues......

Here's a thought, why haven't RV manufacturers(or aftermarket providers) invented a generator PTO off the main engine to allow 240V on the road without the necessity of running the second power-plant? Or for those with the room, couldn't we mount a Generator head to provide engine driven 240 or 110?

AC generators really like a constant speed to handle frequency and voltage challenges easily. Add the problem with dealing with the load while you are trying to be at idle speed at a stoplight or trying to climb a hill and losing rpm...
That is some of why a generator has a semi-purpose built engine.