Ask PYS: PowerEntertainment

Brad, on Jul 15, 2011 asked:

I have a strange situation. I have a radio and a blower fan on my boat. When I turn on the fan, the radio turns off. The fan switch is right beside the radio, but the fan is further forward. Any ideas?

Hi Brad,

This is a strange situation indeed and would be caused by a mistake in the wiring. It’s possible that the fan and the radio are on the same circuit. Poorly wired systems may have both devices powered off of a small gauge (undersized) wire. Because there is more resistance in the thinner wire, when the fan is turned on there could be a large voltage drop, reducing the radio’s supply voltage to the point where it turns off. If this is thecase, this is also a fire hazard, and needs to be addressed immediately!

Another possibility is that there was a mistake in wiring the radio. The fan, when off, won’t create much of a voltage drop, so anyone measuring the voltage across the switch would find 12V when it is open. Wiring the radio to this 12V supply would work – except when the switch is closed. The 12V where the radio is connected to the switch would become 0V, shutting down the radio!