Omnivent Puzzle.

Spanielzrus

Sterling Europa 565 (2010)

Onnivent roof fan not working and traced to faulty motor now replaced with new motor and tested on 12 volts.  Van battery is fully charged.
 All other 12 volt appliances in the van are working pefectly.  

When connected to the 12 volt wiring supply in van the fan wont work.

Voltage at fan power supply cable measures 12.4V. All other 12 volt supplies/sockets in van measure 13.2 volts.  

I am at a loss.  The fan works perfectly when connected directly to a 12v source, just not
with he vans twin wire supply.  Considering running a parrallel connection form a nearby 12volt socket supply.

Any sensible suggestions welcome.

Thanks