Water pump electrics HELP (safari '64)

[Robert Burns]

OK
When I have both switches on the attached image to 'battery' the water pump (from the tank) works fine as do the interior lights (as its 12V DC), but not, obviously, the Air conditioning unit.
When both switches are to 'City power' the pump appears to be getting 20V 'AC' when activated ... so just buzzes and heats up!!!.
SO ... if I want to use the pump from the tank and the AirCon unit at the same time, it appears when I use the 110v input (from home power or Generator) and put the switches to 'battery' I get the pump working fine from the battery (12V DC) as well as the interior lights (12v DV) but the Air conditioner works from the 110v input and the wall sockets are live (110v)
Is this normal? .. if it is I can live with it but if its a PO issue and I have to get a new univolt or the like that would be frightening. I have replaced back area, axle, figured out electrics, plumbing, water and prone including getting rid of furnace and water boiler and am nearly good to go .... PLEASE tell me this is kind of normal and doesn't need immediate attention .... MANY THANKS Rob

[TG Twinkie]

Don't know what year your coach is. But what you describe is not normal. The DC water pump will not run on AC POWER.
The outlets should only provide 120 volt power when you are plugged in to shore power or on generator power. UNLESS you have an INVERTER as well as a CONVERTER.

[Robert Burns]

Hope this helps in my dilemma
R
My safari is 1964 ... the pump IS 12V DC ... and works when switches are to 'battery' but whenever the switches are to 'city power' the water pump does NOT work ... should there not be a conversion from the mains AC to 12V DC to run the pump even though it is on 'city' mode ... or am I mistaken
Best
Rob

[overlander64]

Greetings Rob!

You likely have a problem that is the result of the unusual wiring scheme that was used in 1964 . . . the first year for the standard Univolt. From your photos, it appears that you may have an electrical system that is close to stock. In 1964, the roof vent fans, furnace blower motor, and water pump motor were all connected to transformers that provided 18-Volts DC when connected to 120-volt power. I suspect that a previous owner may have simply cut the wires on the original water pump and installed a new 12-volt DC pump. When operating on battery power no problems . . . when 120-volt AC is connected the 12-volt now becomes 18-volts +/- producing problems. If your coach has the original PAR (Peters and Russell pump), it shouldn't have any problems operating on 18-Volts DC unless its motor has been replaced with a modern motor that isn't rated for 18-Volts+. The solution may be to wire in a resistor or step-down transformer that will reduce the 18+ Volts DC to 12-Volts DC. I believe that this condition was unique to the 1964s as well as a few 1965 Airstreams. Installing a modern 12-volt three-stage power converter charger may also be a solution as the original Univolt wasn't supposed to produce more than 18-Volts DC when connected to 120-Volts AC.

Good luck with your investigation!

Kevin