Shore Power Issue

He posted "Went to turn on lights, AC etc… yesterday but I have no power." and I agree this and more is not clear. It's not clear what DC is working and what isn't. It's not clear if the GFCI is or isn't working only that he saw no change.

It's very unlikely that the air conditioner is on a GFCI circuit and if it is it should be a dedicated GFCI CB in the panel and not a plug. " hit test or reset" sounds like a plug and not a CB.

OP Did you measure 12.4V at the battery? Did you measure 124V on the OUTPUT of the CBs? A tripped CB is not always obvious, turn all of them completely off and then on.

Since the problem occured after repairs I would first expect a fuse or CB either AC or DC, next a open or cut wire either AC or DC. Check for AC at the air conditioner and DC for the thermostat circuit for starters.

Mikes last statement is good advice. It can be helpful to give make/mode of the RV and equipment.

It's not the most clear info but where did the OP say he didn't have lights?

He says the DC items are working fine, so likely not the DC side.

Also, the battery at 12.4v might indicate the battery charger is not getting 120v AC power as that should be up around 12.7v (higher if the battery charger is actively charging). Battery isn't dead but it might not be charging.

Do any of the outlets have power (not all may be on GFCI)? Try pulling the GFCI outlet and test the wires feeding it to see if it has 120v power.
- Yes, it's probably GFCI related
- No, work your way back upstream towards the panel until you find 120v power and that should narrow down the issue.
- I'm guessing not GFCI as it won't take out everything 120v.

If you need more help, tell us what items are and are not working as that will help narrow down possibilities.

Lights in an RV are usually 12 volt. So if they are not working CLUE
A/C usually uses 12 volt for Control.. Furnace is a 12 volt device.
Fridge and water heater use 12 volt for control.

If you have a pair of 30 amp fuses on the fuse panel I'd start by checking them.

How to check fuses the easy way... A TEST LIGHT
You can get a test light at most any auto place Prices and quality vary but most all are good if you follow this procedure Also get a coil of wire and the kind of clip you find on the test light Same store shoudl have 'em

The Test light looks like an old fashion ICE pick. clear or translucent handle and a wire with a clip coming out it.

Clip the clip to a known good ground (Negative wire)

Touch the tip to a known good 12 volt Bright light good. Dark reseat the lamp and try again (Testing the light)

now on the fuses each end has a small window
Bright/Bright = Good
Dark/Dark = No Test
Dark/Bright or Bright/dark = Bad fuse
NO NEED TO REMOVE FROM PANEL.

The coil of wire.
Sometimes you need to go some distance to find a good ground.. Strip bit of both ends of the coil.. then re-roll it up with the bare end poked into the middle.. On the other end put the clip. use it as an "extension Lead" by clipping on a known good ground (battery negative?) and then unroll to test area and clip the clip on the exposed end in the middle.

Likely a DC problem. Could be a blown DC fuse or tripped DC CB. Use your voltmeter and track down voltage from battery to the lights for starters.

GFCI only effects 120V AC plugs so you can retest with say a light plugged in.

"DC power works fine. Just no shore power."
??? You don't have lights so no DC to them. You have 120VAC at the breakers so shore power is OK.

FYI Your new A/C may require DC for controls.