Marine Air second air handler fan not kicking on

Marine Air second air handler fan not kicking on
Owner of a 1997 Cranchi Zaffiro 34. Has a 16K Marine Air A/C and heat system with a Passport I/O controller. Boat has a galley/salon, a bow stateroom and a midships stateroom.

System's compressor is located in the engine compartment and has two air handlers located under the galley seating, a 9k unit that conditions the galley and a 6k unit that conditions the two staterooms via a rheostat for the fan speed that's located in the forward stateroom.

The issue: The fan for the 6k unit does not kick on when the compressor and rest of the system turns on, to include the fan for the 9k unit. Rheostat position does not cause the fan to come on. When power jumpered from the 9k fan power feed, the 6k fan comes on, but will cause the A/C circuit breaker to pop after about 7-10 seconds of operation.

Second issue: 9k unit evaporator is icing up, initially at 65 deg commanded temp but also at 72 deg commanded temp. 6k unit evaporator is chilling, but only partially icing. I'm unsure if the two units are in series or parallel with regard to refrigerant flow. 9k unit icing could potentially be caused by lack of fan over the 6k unit?

What's causing the 6k unit fan to not come on, and then trip the breaker when jumpered? I have the generic wiring diagrams for the system but I'm not seeing a clear issue. Obviously there's a short somewhere, but why not trip the breaker instantaneously?

What's causing the 9k unit to freeze over? The 6k fan not removing the thermal cold load off the system?

Thanks in advance!

Thanks Ralph, I suspected that was the case with the icing.
Boat has a 30A 115V service.

Jumper is 12 AWG wire using posi taps from the hot and neutral of the 9k fan power feed to the hot and neutral of the 6k fan power feed. Sounds like if the one leg was then powering both fans perhaps it pulled too much amperage and caused the breaker to pop. The system wiring diagram I have only shows one fan with L1 and L2 connected to it.

The manual fan control at the I/O panel does control the fan speed on the 9k unit.

I also love a little hooch!

Background: Bought the boat last November...I remember the 6k fan running during the survey as the exit ducting is loose on the front of it and so I felt the air coming out of it.

No recent work on the boat, however it did set at the marina through the winter. The fresh water tank pump was replaced, as well as fuel filter service, oil change, drive oil change.

Boat was towed 6 hours to get to its current location in February.

As the wiring pigtails from the fans look identical, I tapped them on the pigtails on the matching colors. So yes, I'm assuming they're wired the same and L1 and L2 are the same colors at both fans.

I do have a DVM, however I did not verify which was hot and which was neutral, see above regarding factory wiring, no work on this system since the survey, and the fact that the fan worked during the survey.

Sounds like I need to try to trace the current power source for that fan and go from there. It almost looks like it comes from the 9k unit, over to the rheostat in the forward berth, and then back over to the 6k fan after going through a box of some kind.

I'll try to post some pictures.

Because of the ducting issue, I can shove my hand in there and it spins as easily as any other 12V squirrel cage fan I've ever encountered. I'm wondering if there's a relay or something out. Doesn't seem to need a starting capacitor for it.

Automotive applications of roughly the same size, amperage, purpose, etc.

Got it fixed. J box that had the circuit board inside it was a two unit version. Had spots for ships power, pump, unit 1, unit 2. Somehow the second unit was wired to the pump spot. I put it over onto the terminals for the first unit and it fired right up. System now works as advertised even though there was a large burnt spot on the circuit board...probably caused by when I back fed 12V into the "pump" terminals because it was wired that way. The unit two terminals had no power to them, and adding a jumper from unit 1 to them would have achieved the same thing.

Bottom line, it now operates and does not ice up.