Reverse Polarity Light when running Generator

[VolNavy91]

OK here's a weird one for those of you that understand AC power better than I do. I have a '97 400 with twin 30 amp inputs and a 4.2k westerbeke generator. No issues on shore power. No issues on Generator with panel one (galley, outlets, HWH, charger). On the Air Conditioning panel no issue when I run the pump or the forward AC unit. But when I turn the rear unit on I, the reverse polarity (red) light comes on. This only happens when the generator is running. Any ideas?

[KandJ72]

Just for verification have you gone through the process or running just that one A/C and nothing else on gen just to see if it's not a load issue. If so 1st thing I'd check is ground on that A/C. I worked on RV's and travel trailers for many years and 90 +% of the time Gen and A/C issues (as well as most electrical) is ground. It could very well be your getting a little feedback through that circuit and running on Gen power is a little dirtier and its just enough to trigger that light.

[Viper]

+1, I agree. Check your connections and do a good visual at the wiring on that AC unit to ensure the condition of the wires, their insulation, and connections including harness plug pins are clean and in good shape. If all is in good shape there, open the junction box where all the units plug into and check that unit's wiring/connection there as well.

[VolNavy91]

Thanks y'all. I will check it out. It seems to only be when that A/C unit is on, whether or not anything else is pulling on the generator. On shore power no issues.

[bud37]

Qr Bbpost Thanks y'all. I will check it out. It seems to only be when that A/C unit is on, whether or not anything else is pulling on the generator. On shore power no issues.

When on the generator the power returns to the generator vs returning to the shore service. So the AC unit and the generator have the boats bonding system in common, something to consider as well as the AC unit's possible wiring problem, now whether that would light up the reverse polarity light I don't know at this point.........good luck and be careful when working on 120 volt power systems.