Converter works only when Air Con kicks on

[SailBonnie]

Hello! New to RVing, just purchased 2012 GS Visa travel trailer after Hurricane Ian destroyed my home. The trailer is plugged into 30A, 125V shore power. I am having issues with the DC power. I noticed lights would "brighten" sometimes when the AC Compressor kicked in. Was intermittent, but became progressively more frequent. It appears the converter is not charging/fully charging the battery. It got to the point where the battery got so low, none of the 12V system would work (lights, water pump, fridge - even though set on 120VAC).

I put a meter on the battery, approx. 10VDC. I replaced the battery, but the issue persists.

I have 120VAC at the plug, and at the trailer main breaker. I have 120VAC at the converter breaker. I have 12VDC at the battery... BUT after an hour or so with lights and water pump on, the battery dropped to 10.8VDC. When I turned on the Air Conditioner, the battery voltage came up to 12.4VDC.

More trouble-shooting: I disconnected the battery cables, and measured voltage at the converter PC board. I had 4.3VDC. When I turned on the Air Conditioning, the Converter output jumped to 12VDC. I checked all the lugs on the breakers, neutral bar, PC board, battery terminals, etc. Everything is tight. No obvious burned wires, connections. Converter fuses are good.

Is this a bad converter, or bad start cap on the Air Con? Thx!

[RY469]

Converter is not performing. The output should be around 13.7VDC given conditions you described. Your A/C >SHOULD< have no effect, interesting it does. Will the extra AC load from the microwave do same thing?

[THenne1713]

My suspicion is maybe a bad 120vac neutral at converter, and load is improving connection (but not curing) that condition. Measure 120vac input to CONVERTER? HAVE READ MANY POSTS about a bad crimp splice causing issues. Also check for loose screws at breaker and neutral strip on 120vac side feeding converter? If OK, Then measure the OUTPUT?

Maybe just bad converter, but something fishy...

[SailBonnie]

Originally Posted by RY469

Converter is not performing. The output should be around 13.7VDC given conditions you described. Your A/C >SHOULD< have no effect, interesting it does. Will the extra AC load from the microwave do same thing?

Thanks for the feedback and info! I haven't tried monitoring converter output with the microwave. The first, and only, time I used the microwave... I tripped the shore power breaker because the Air Con was also running. I guess the load was too much for my 30amp breaker. I will try the microwave (without Air Con!) tomorrow.

Yesterday, I heard a "buzzing" noise in the trailer. When I measured the converter output with my trusty Fluke, it was fluctuating from 12.8 to 13.5VDC.

I'm starting to wonder maybe a bad chassis ground? Everything else is tight in the electrical panel. Maybe the vibration from the Air Con unit causes the chassis ground to make contact? It's a mystery....

[SailBonnie]

Originally Posted by THenne1713

My suspicion is maybe a bad neutral at converter, and load is improving connection (but not curing) that condition. Measure 120vac input to CONVERTER? HAVE READ MANY POSTS about a bad crimp splice causing issues. Also check for loose screws at breaker and neutral strip on 120vac side feeding converter? If OK, Then measure the OUTPUT?

Maybe just bad converter, but something fishy...

I agree! Something is very fishy.

I'm starting to suspect a bad ground/neutral somewhere - maybe at the chassis? I checked all the connections in the panel - converter breaker hold down screws, ground bar, neutral bar, converter pc board, etc. I have 120VAC coming into and out of the breaker.

Yesterday, I heard a "buzzing" noise in the trailer. When I measured the converter output with my trusty Fluke, it was fluctuating from 12.8 to 13.5VDC.

If it helps, I am in sunny, hot and humid Florida. I'm wondering if corrosion, or loose wiring is my issue.

Thx for all your assistance!

[THenne1713]

I have read of older CONVERTERS that blow out a solder joint on a circuit board when overloaded, or load simply uncovers a bad solder joint, and repair is simply resoldering?

<<
I'm starting to wonder maybe a bad chassis ground? Everything else is tight in the electrical panel. Maybe the vibration from the Air Con unit causes the chassis ground to make contact? It's a mystery...>>

120vac GROUND SHOULD CARRY ZERO CURRENT AND SHOULD BE totally ISOLATED FROM AC current-carrying NEUTRAL inside an RV. 12vdc chassis NEG/ ground is totally another issue.

Loose/bad crimps in connections are a common cause, based on what I read. Watching video earlier today on connections, a wire not properly stripped in a WAGO connector showed voltage w/ Non-contact tester, but Voltmeter showed ONLY 4-vac vs 120vac.