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My 1954 Cavalier came with add-on A/C already installed.

The compressor is Sanden, The Evap unit under the dash has a small control panel close to the driver side with a fan switch and a temperature control. The main Evap unit is under the passanger side.

So . . . . . . .

I acquired a 30 LB jug of R-12 from a friend and added some to the system which is marked R-12, I have no idea what was in there.

My system has a sight glass.

Upon initial test this morning the compressor cycled on and off frequently, maybe due to temperature, I don't see any other controls.

After the charge of R-12, plenty good cold air is coming out.


My 12 volt battery was down as the 12 volt alternator seems short on capacity.

Good proof the compressor clutch won't engage much below 12 volts.

The ride home tonight at 110 degrees of Phoenix heat will be the test.


The alternator is going to be a pain to remove. A solution could be to find or build a 6 volt fan for the Evap.

If I had the parts I would put it back in the trunk.

Jim

Jim.
Your A/C ought to have at least high and low pressure switches. A high pressure switch is imperative so you don't blow up A/C !!!, the low pressure switch to prevent the compressor oil to be sucked out, thus ruining it.
If the compressor cycles off and on frequently, my guess is that it is caused by one or both of the switches. Too much or too little R12, blocked expansion valve (by moisture?). It also might be a wrong type of refrigeration gas.
Perhaps the unit needs to be vacuumed and checked for leakage.

Tom

McDermaid indicates a Sanden pump. I assume that to be a relatively modern pump. But he makes no indiction as to what the rest of the system is and/or age of rest of the system.

Possible that it does not have hi/lo switches. Maybe just a t'stat that inserts into or is attached to the evaporator to shut the pump clutch off or on depending on evap temperature.

My 50's Mark IV system with 85'ish toyota pump and dryer has only the t'stat switch on the evap. Mark IV factory manual indicates no such hi/lo pressure switches.

However, the 85'ish Toyota did have a pressure sw on the dryer, but that was a toyota design. It gave problems. I eleminated the Toyota hi/lo sw and simply used the t'stat sw. That was over 10 years ago and the system works just fine now for over 25K miles.

Botom line:
If miscelaneous AC parts are grafted together then variations in the external controls may need to be experimented with. In my case i never could find a pressure sw. (went thru 3 of them) that would work rite. Had a lot of cycling off and on trying to use pressure sw.

McDermaid. U indicate alternator problems. What kind of alternator are u using.

As far as I know the Sanden rotary compressor for use on car A/C, has a high pressure safety relief valve at the rear end.

Tom

I'm guessing the add-on A/C is junk yard parts.

I conclude the compressor is cycled by temperature only, no high / low pressure switches.

I had mostly foam in the sight glass and charged it until it was just clear, I Don't have a vacuum pump. The compressor is labeled R-12, I can't see the top of the expansion valve. It makes plenty of cold air now.

The R-12 was a stab in the dark as I have no idea what the system was originally charged with. They make a test set that actually tells you but it costs 2 grand.

Driving it home from work last night with about 110 degrees of outside temp and sun on the dark blue top, it was cooling just fine and the compressor cycled off several times. I had to turn up the temperature control to get it to cycle.

Cycling is good because it lets the load of the clutch off the 12 volt system (it is running that close).

I don't know what the little alternator is from. I may have to remove the bracket that holds both the compressor and alternator to get to it (Several head nuts and bolts on the water pump) I don't want to remove head nuts. It appears Japanese made has a two wire plug that was direct connected to the 12 volt output terminal and possibly ground. It will run the 12 volt battery up to 14 volts without a load. It doesn't charge when stopped at a light.

The single belt setup is not adequate the type X belts break frequently I haven't tried a standard belt. The belt slips unless it is tighter than I like. Not enough belt wrap around the fan pulley without an idler which bends the belt backwards.

My car has a single belt crank pulley.

I use the vents all the time and never suck in outside smells unless I am behind a grease burner. I figure I can crack the a vents and get some fresh air. I have no reason to believe monoxide gets into the cabin. The reason I quit running Corvairs.

Jim

As this thread is about to pass off (as it probably should) I have continued to analyze my add-on A/c.

With a full refrigerant charge the unit will cool the car just fine.

problem is the 12 Volt alternator. In the space available even a better alternator won't get enough belt contact.

As long as I am moving and the fan is on low it keeps going but on long light and the 12 volts fades down to 7 and can't get charged back up.

A 6 volt fan would solve this. The compressor clutch is also a big amp suck, and it needs above 7 volts to grab.

Temperature in Phoenix is 110.

Jim

You'll never get the system working right without a vacuum. Air in the system causes pressure problems and moisture in the air freezes at the Expansion Valve.

There is pitifully little R&D on HVAC. About the only thing they have done is develop meaningless gadgets. Other than that it's hand grenade engineering.

Quote:

Jim, as you know, I've followed your posts and traded information with you on the subject of your AC with a great deal of interest and I've learned a lot from hearing about the setup on your car so thank you for sharing the details. Your setup is quite unique to other systems that I've looked into and it's really not a bad design at all. I may even look into something similar in time. If you have the opportunity, you might want to consider installing a belt groove type idler pulley and mounting it somewhere that will provide more belt wrap on the crank pulley, I wouldn't be surprised if that doesn't solve your belt wear problem, Ford used an idler back in the late 60's and into the 70's that made it easy to adjust belt tension and also should be quite easy to make a bracket for mounting it on your engine.

I certainly appreciate the guidance of the group and the sharing of information.

The refrigeration is working real good and the air coming out of the evap coil is down in the 20's. It is so hot and dry here in Phoenix it will never ice up. Topping off the R-12 fixed that problem.

The 12 volts is the remaining problem. I need to find a "VEE" belt that can take a reverse bend for the idler I already have.

The 12 volt alternator may just not be working properly and that could be part of the solution.

I was going to see if I can come up with a simple DC to DC converter that gives me enough 12 volts to run the fan or a 6 volt fan motor. This to get by the heat season here in Arizona and then I will look for a real fix.

The 6 volt heater fan under the hood pulled about 8 Amps but I don't believe it has enough air flow for the A/C.

Thanks, Jim