Electrical help 24 v engine room fans.

[Bjelland]

Hi,

I am in the process of fixing up an old Moonraker from 1974 and I have a question regarding wiring of the 6 engine room fans the boat was fitted with. The original set up seems to be that the 6 fans have operated from a single switch on the console. Within the wiring there were some resistors?? Or something that were crispy after 40+ years and have fell apart.

Consequently the fans have not worked for a while so I have removed these and tested each one direct from a battery and bingo they all function.

Having a limited knowledge of electrics I am hoping someone from the forum can tell me what I need to get this system up and running again, I know I cannot connect the 6 fans directly to the switch and some form of relay or controller is needed.

The fans are 24 Volt and I guess 4 amps each comparing there size to new units.

Thanks.

[C lectric]

I assume your boat system is 12V?

You say the fans are 24V? If you tested them on a 12V battery they would run but at quite low power/speed. Are they really 24V?


THe fans can/should be run from a relay. Cole Hersey makes suitable models, just pick a continuous duty unit. That relay can then be controlled by your dash switch. The relay will need to be connected AND FUSED at the feed point. You will need at least a #10AWG wire and even better a #8AWG. for both the + & - sides of the circuit.

THe panel switch can then feed the relay. That could be a #14 AWG.

It's possible the crispy critters were resistors used to drop some voltage to the fans which would also reduce the current draw to the fans. THat would have been owner driven so no comment unless ONE of them shows enough marking to get some info. Ohms, power rating for a start or the mfgr. name and p/n sometimes are on them. Have you tried to measure the ohms on any of them? Even though crispy they may, one of them, still show an ohms reading. From that you can either replace them or estimate what he was looking for as a Vdrop.

I'll guess he over fanned so used the resistors to reduce the blower power.

Or you could just use fewer of the fans and ignore the resistors.

But confirm the fan voltage as the rest doesn't make sense if the fans are truly 24V running on a 12V system AND using resistors inline. It's possible of course that if really 24V fans they still blew to much so he dropped the voltage even more.