Fan is thermostatically controlled, it comes on when it gets hot, if the air surrounding the unit is cold enough, it will never get hot enough to fire up the fan.
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Upgrade, on the list of converters where units like the Progressive Dynamics 9200 (or in your case 4600) and IOTA with IQ-4 and a host of others are at the top of the list
That magnetek 6300 comes in dead last.. UPGRADE the thing.
The 4600 replaces the ELECTRONICS in the magnetek so you keep the same distribution panel, way cheaper than replacing the entire thing.
Randy at Best Converters can provide help, the web site instructions.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times