IP38 Engine vent fan circuit

Would be grateful for circuit diagram of the engine room vent fan, 1990 IP38. How do you switch fan off/on???? Is is designed to cool alternator? Thanks!

My 1993 IP38 does not have an engine room vent fan. Not sure if IP stopped using them or if you have an addition made by a prior owner. If it's an after market install you may just have to trace the wires from the fan motor and see where they terminate if none of the existing switches turn the thing on. Likewise, check the power at the fan motor with various switches on/off. You could just have a bad motor or bad connection.

Thank you very much for the prompt reply. Interesting you note that your 38 does not have a vent fan. Explains why there is no circuit description in the IP manual. Could well be after market. There is no switch in the obvious place on the engine panel in the cockpit.

Do you have any form of ventilation even passive?

Would like to hear from anyone on the merits of ventilation for this boat.

Passive ventilation always comes from the engine itself. Our 4JH2E engine is 100 cubic inches. At 2500 RPM it draws in about 140 cubic feet of air per minute through the air intake. That completely cycles the air in the engine compartment about 6 times a minute. That air comes from other parts of the boat (bilge, lazarette, and boat interior). I've got an aftermarket 100 amp alternator with the regulator inside the engine compartment but with no special ventilation for either. Both have worked fine for 10 years since installed. So not sure if an additional dedicated blower is really needed. Wouldn't hurt though if you can get yours running. I wouldn't loose much sleep over it if you can't.