So, a summary so far:
~ You believe you are connected to 30 amp shore power...plenty to run an AC.
~ The inverter (for your residential fridge) should have nothing to do with the AC. AC is such a power hog that essentially NO RV battery bank is big enough to run it, so AC is 120 volt shore power only. If your fridge is running on shore power, that does NOT mean that the inverter is OK, but what this does mean is that the inverter should not come into play in diagnosing this problem. (Most inverters have a transfer switch that chooses 120 volt shore power when available and simply passes it through the inverter. When the transfer switch detects NO 120 volt supply, it switches to battery and runs the 12 volt DC thru the inverter to turn it into 120 volt AC.)
~ Your converter should supply 12 volts and should do so without a battery. Do all other 12 volt appliances work? Lights, slide, furnace, water pump? If so, the converter is good and supplying 12 volts as it should. If not, that's an issue.
~ You operate the thermostat, and it triggers to make the AC FAN run, but the
compressor in the AC does not appear to start. Only the fan operates.
~ You have not commented on resetting breakers and/or checking fuses.
TURN OFF EVERY breaker, then turn them back on. You must turn off a breaker before you can reset it. Many appear to be on despite being tripped. If it appears to be tripped, you CANNOT just push it to the on position without turning it off first.
PULL EVERY FUSE and shine a flashlight through it from behind. Blown blade fuses are notoriously difficult to diagnose while still in the panel.
Test the AC. No go?
~ While waiting for your new battery, get ANY 12 volt lead-acid battery (even from your garden tractor) and install it...just for giggles...and test the AC.
No go?
Now it's serious. There may be a problem with the AC compressor or an add-on hard start system.
~ Start at the beginning. Use your multimeter (see below) to check that you ACTUALLY have 120 volts at the pedestal. A bad connection somewhere along the way to the pedestal could cause a voltage drop that would cause the AC compressor to fail.
NOW BE SURE YOUR SHORE POWER CABLE IS DELIVERING 120 VOLTS ON THE END THAT CONNECTS TO YOUR RIG. Use the multimeter.
IF YOU CAN, trace the cable connecting the shore power connector on the outside of the rig to the back of the converter. Check the connections there...at the screw terminals on the back of the converter and at the socket mounted to the outside wall of your RV. Make sure all connections are solid and tight. Loose connections cause voltage drop.
Wiggle the plugs at either end of the shore power cable, and shake the cable, and monitor voltage...any fluctuations indicate a problem with the plugs or the connection in the sockets.
Anywhere along that pathway, there might be a problem. And if your AC does NOT have hard start assist, the AC will likely refuse to run on what you presume to be good shore power. Everything else in the rig may disguise this problem. You can successfully adapt your 30 amp plug to a 15 amp plug and pretty much run your whole camper...except the AC. Bad connections can pass enough power at lower amperage to fool you.
If you really have a 30 amp shore power supply...
~ LOOK FOR a large "hard start" capacitor.
If you find one:
THAT could be the problem.
OR USING ONE may have damaged the AC compressor.
WARNING: a fully charged and functional hard start capacitor will knock you on your ass. The job of the capacitor is to store a huge jolt of energy to assist with starting the compressor motor. It is charged with 120 volts, and it can deliver substantial amperage. A multimeter can test the voltage and capacitance of the hard start capacitor.
Once that's ruled out:
~ The last ditch DIY effort would be to trace and test the wiring from the thermostat to the air conditioner using a multimeter to check both voltage at the thermostat and "continuity" of the wiring to the AC control box in the AC unit.
Multimeter:
https://www.homedepot.com/p/Stalwart...B&gclsrc=aw.ds
Use multimeter to check voltage:
Use multimeter to check continuity:
For this, you may need to jury rig some alligator clips and wire to extend the reach of your multimeter.
https://www.autozone.com/miscellaneo...B&gclsrc=aw.ds The goal of the continuity check is to ensure that your thermostat wire makes it from the thermostat to the AC unit undamaged.
Also check all connections at both ends of the thermostat wire AND check the power connections to the AC unit. There should be 120 volts into the control box on the unit, and all wires should be solidly connected. Pull the plug on shore power BEFORE you pull and reconnect wires (usually spade terminals or screw terminals), BUT DO NOT TRUST A HARD START CAPACITOR. The capacitor can hold a charge for months or longer, so always behave as if this is LIVE and dangerous...including if you choose to remove and replace it. Both the old one and a brand new one may have residual charge!!
Note that 120 volts in its own right is unlikely to be lethal, but the shock can hurt, cause a fall, lead to secondary injury as you jump back and so on. If you choose to replace or install a hard-start capacitor, use electrical tape to shield the connections on the capacitor.
None of these tests are precision tests. They are more all or nothing, so your skills with the multimeter are not critical. It's not "is it 12.3 volts or 12.7 volts?" It's more like, "is it 0 volts or 12 volts +/-?"
If you don't discover anything obviously wrong - like half the 30 amp pedestal being dead, a disconnected wire, an obviously destroyed capacitor in the hard start, or no 12 volt power at the thermostat, or bad wire somewhere, it's time for a pro to look at your AC.
Linear Mode
