Re: Modern AC Compressor in a 6-Volt Car

Posted by Jim McDermaid On 2014/2/4 11:08:51

We have blogged about this several threads ago.

As my 54 Cavalier has a separate 12 volt system (alternator and battery) to run the Add-on A/C.

I have done some research:

First, a compressor clutch on a Sanden draws 3 or 4 Amps at 12 volts. Nobody makes a 6 volt clutch and the original compressors ran continuous unless you took the belts off for the winter. The clutch won't engage much below 7 volts, and not at all on 6 volts.

The other big power suck is the blower for the A/C Evap unit inside the cockpit which as I recall was drawing about 15 Amps on high speed.

My 12 volt system can't keep up on a good summer day in Phoenix AZ.

My solution is to see if the blower can spin the proper direction and run fast enough on the 6 volt system. (I realize I won't get high speed). If the blower motor is permanent magnet type I will have to flip it end to end and change the squirrel cage back. I rarely run the blower faster than low speed which cools just fine especially with R-12.

Haven't had time to pursue this yet.

I could then keep the existing 12 volt system which will have no problem running the clutch. Or buy one of those 6 to 12 volt converters for just the clutch.

The A/C system draws way too much power to try and run it on a 6 to 12 volt converter as the 6 volt system is good for about 45 Amps from the generator and the load from the converter calculates to about 45 Amps.

My 12 volt system is totally separate from the cars original 6 volt system. I use an Optima 6 volt battery which leaves plenty of space on the battery shelf for an RV type 12 volt sealed Glass Mat battery. The Optima's are sealed also so no corrosion.

The 12 volt is handy for using my engine analyzer and timing light. And I am looking for an FM to AM radio converter as all the AM's in Phoenix have gone hate talk.

Jim