Dc lo keeps blinking on the fridge and lights go low in rv, power converter middle light is blinking green

The fridge in your 2012 Sterling 32RL is most likely a 2-way refrigerator. This means it can operate on two power sources: 120-volt AC power (shore power or generator) and propane gas.
Typically, 2-way refrigerators do not operate on 12-volt DC power directly. However, some RVs may have an option to run the refrigerator on 12-volt DC power while driving, using the vehicle's battery system. This is usually done through an inverter or a converter that converts the 12-volt DC power to 120-volt AC power to run the refrigerator.
To determine the specific capabilities of your fridge, it is recommended to consult the owner's manual or contact the manufacturer of your RV or the refrigerator itself. They will be able to provide you with accurate information regarding the power options and operation of your specific refrigerator model.

I go with the converter solution IF you have controls set properly. I have use a 12V trickle charger (relatively inexpensive) to verify and supplement a weak inverter. Since you said your hook to AC you have power for the trickle charger.

DC voltage is to low.

sounds like one leg of the main breaker is tripped need to reset. also the a/c's in a rv require dc to operate controls. check those fuses

Should have the basic schematic in your owner's manual. If not, contact the mfg and see if you can download one or have it mailed.

No luck? Google it. If persistent enough, you can find one.

The Parallax 7155 converter should not require battery support for any 12 volt load amperage that is less than the maximum amperage capacity of the converter. A standard RV incandescent 12 volt lamp draws about 1.5 amperes for each bulb. With the battery disconnected and other 12 volt loads off, turn on lamps (not fixtures) and calculate the number of bulbs which can be turned on. If you run out of lamps, turn on vent fans etc. The idea here is to try to get to 55 amperes of DC load if possible without going over 55 amperes. At a sustained DC load of about 25-30 amperes or higher, the fans should cycle on continuously after about 5 -10 minutes. Lamp brightness should be normal and the measured voltage from the converter should be above 13 volts if under 55 amps of DC load. If the voltage drops with only a few lamps on, a converter issue would be likely.

Diagnostic tests an RV technician should make would be to:
1. Disconnect the battery system.
2. With the converter system powered on, measure the DC amperage with a DC ammeter capable of reading at least 60 amperes DC from the blue lead at the DC fuse panel terminal VCC.
3. Measure the DC voltage at terminal VCC and DC ground.
4. Record both readings.
At any DC load amperage less than 55 amps, the voltage should be above 13.0-13.2 volts DC. This method should take out all guesswork and confirm a DC converter section issue or not.

This is an RV frig correct? It SHOULD work either/or. AC or DC. If your plugged into AC then often the frig will work with that alone. DC is for when you have no AC so you can power your appliances of the battery. Maybe you have a converter (AC to DC which most RV's do) that somehow is not getting the DC to the frig.

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You said there was NO lights on the unit. The Dometic service manual says:

1. No operation - no panel lights: DC Volts

Fuse

Wiring

Upper Circuit Board

Lower Circuit Board

http://www.gasrefrigeration.net/dom_techdata/26121_2852SM.PDF

I would start with the DC volatage and track it back until you lose it. Most of the time it does end up being the lower circuit board though.

Check any fuses/circuit breakers in harness from battery. That battery should supply 12 volts dc to fridge lugs/terminals at bottom of fridge on outside behind vent.
If battery is good and hooked up properly but no 12 volts to fridge, then you will have to trace back to battery for broken /bad wire. If you want to test quickly, just run 2 jumper wires from battery to those 2 lugs marked + and - Battery + to + (pos)at fridge, and - battery to -Neg at fridge. That should allow you to run it on propane or 12 volt. Remember, running it on 12 volts will kill that battery pretty quick, unless it's being charged. When you are plugged in, the converter supplies the 12 volts to your fridge, as well as should be charging your battery.

Its late, so just to make sure I'm not brain-dead basically your laptop runs fine as long as its powered by the AC adaptor but dies fairly quickly while running via battery. This is very typical of a battery that will no longer hold a charge, not normally a user repairable item. It could also be that the charging electronics (in the laptop) isn't charging the battery, again not a typical user repair job. About your only option short of taking it to the repair shop is buying or borrowing a battery as a test.