Low voltage into ATS

[Go Poly]

We have not used our 2019 GT5 since May and started the process of checking out systems before planned trip in October. So, we hooked to shore power to run refrig, then when satisfied, unhooked from shore and turned on generator (onan 5500), refrig operated, then turned on on Air Conditioner unit, it came on; then attempted to turn 2nd unit on and click noise occurred and all shut off.

We then ensured all electrical draws were off and checked all circuit brearkers. No tripped breakers found. Turned on generator and this time auto transfer did not occur. No voltage increase noted on readout.

So, did some reading then went to ATS (auto transfer switch) pulled cover and performed voltage measurements (as indicated in troubleshooting section of manufacturers paperwork). Both input voltage and switch output voltage. Input voltage read 55 volts AC (should be 105 to 130) and 0 output volts (should be 105 to 130 if switched).

Question is: what faulted between generator and input to ATS to result in odd voltage? What did we do to cause this type of failure? I would think that if we caused a voltage overload a breaker would have tripped?

Help me!

Thanks for any insight!

Scott

[Go Poly]

120 v AC

[mercury9]

I believe mine has a breaker on the generator itself

[NavyLCDR]

Check the circuit breakers on the generator itself.

[Go Poly]

There are two breakers on the generator. Neither were tripped, but a switched on and off just in case. No change.

[NavyLCDR]

I would check generator output voltage at the connections of the cables to the output of the generator breakers.

[Go Poly]

Generator output:

1). Both breakers switched on: 50 to 55 VAC
2). Both breakers switched off: 0 VAC
3). Upper breaker off, lower on: 50 to 55 VAC
4). Upper breaker on, lower off: 22 to 27 VAC

[Go Poly]

Therefore there were no fault codes.

[Go Poly]

No conclusion, yet. Talked to many experts......either wiring from gen to ATS (makes no sense to me since it worked fine prior to event), faulty brushes (makes no sense due to some output voltages measured as reported above) to the final, and most likely culprit, the gen control board.

I will report back once final fix implemented.

[Go Poly]

Ok, so I figured I would report back once my predicament was solved.

Recall I left this forum thread regarding an odd generator output voltage, as measured at the transfer switch. I thought it best to take rig to authorized Cummins/Onan repair/dealer in case this could be a warranty item (less than 2 years since purchase).

The technician promptly measured generator output voltage AT THE GENERATOR and determined that there was no issue with the generator. I.E. proper 118VAC out. So, issue must be between generator and transfer switch. Upon further investigation they discovered a junction box not far from the generator underneath the rig. Upon removing the cover the technician discovered a melted wire nut. The large gauge wire from the transfer switch was attached to the smallish wire from the generator using wire nuts! OMG! Apparently the high resistance of this less than robust connection created a perfect storm when I attempted to start both AC units simultaneously.

Lesson learned in my specific case (per wife): Do not attempt to power up both AC units simultaneously.

Additional lesson learned: measure voltage at generator proper, as recommended by NAVYLCDR.

Recommendation to manufacturer: Consider using some type of "high current" terminal block with screw or lug thread type connections. I would think this would be much lower contact resistance and therefore lower electrical resistance (and less variation from connection to connection than wire nuts, perhaps less susceptible to corrosion as well)