Re: Random questions about 51-56's, Ultramatics and A/C

Posted by HH56 On 2018/3/8 10:44:22

Most of an AC system is mechanical, not electrical. So the 6V is really about the fan and the method of compressor engagement if any and ice prevention


Very true. Aside from figuring out your compressor mount and belt drive the other problem is electrical. Aside from air delivery, the other issue is today all ice prevention is done by the clutch turning the compressor on and off.

If you get a bare bones non electronic control under dash or trunk setup with a single blower wheel and resistance speed control the fan motor may be able to be changed out to a 6v universal heater motor. Some fixed 3 speed as well as resistance speed 12v blower motors will also work on 6v but at a reduced speed. In either case there are some sacrifices as far as power and ultimate air volume delivery. Units with modern solid state electronic control for blower speed and temp control cannot be used..

Heater motors are a bit smaller than AC motors and are only single shaft. For a typical underdash unit with dual wheels there seems to be no 6v double shaft motors made. You either need to get creative in driving dual wheels with a single shaft or use a single wheel unit or get one of the units that have a motor that can work at 6v.

The Sanden compressor clutches will pull in at about 7.2 volts or so and if the generator is functioning at its normal output of approx 7.4v several have reported the clutches will pull in and work satisfactorily. While several have reported seeing 6v cars with modern AC systems installed, to the best of my knowledge none of the people with one of the 12v systems working on 6v has given specifics as to what unit they have or what might have been done to make it fully functional.