Fridge running on AC won't work ...

Hello everyone,
Probably missing something obvious, so I figured I'd try here ...
2006 Fleetwood Bayside, had the unit plugged in for a couple of days, fridge did not cool.  Set it on AC, turned it up to 5 (out of 7) and got nothing.  Got to the park this past weekend and tried again, still nothing.  Ran it off the LP and it ran like a top !!  Used the battery to maintain temp. while travelling the 2 hrs. home and it stayed where it was.  Flipped back to AC and the temp. shot up again ...
Could it be low on Free-on ?  (I know I didn't spell it right).  Does the fridge rely on free-on only when on electrical or with LP and battery too ?  Not sure where to look next ?

tx
Caper

First let me ask you.... Does the unit indicate that it is running on AC?

Several issues come to mind.....

No indicator (As opposed to no indication) means you have to chase power

No indication (But there is an indicator) means you have lost AC or.. The control board.  Check your circuit breaker, check for AC at the control board

AC good at the control board... Heat element burned out or bad relay or bad control board.. Check for AC to the heat element, if it's there that's the problem (heat element) the relay is part of the control board

No indicator on this unit, simply a flip of the AC button, and a setting from 1-7 ... I tried the outlet that the fridge plug into with another device and there is power to that point ... that's about as far as my trouble shooting skills go ... 

Your fridge has no freon at all, in any mode. It's a gas absorption fridge and operates on a different principle entirely. The same cooling unit is used with electric or gas, so no problems there.

It sounds as though there is a problem on the 120vac side of the circuit board. There is probably a fuse for the 120vac mode heater, or the heater itself may have failed. Since you lack basic electrical skills, you are probably going to ned professional help.

By the way, what brand and model of fridge is it? That would help us diagnose it better.

Dometic RM 4223

A bit of additional information FYI to what Gary said.  The absorption cycle works by heating a fluid (used to be water and ammonia) until it reaches a temperature where the ammonia is released from the water as a gas and used for cooling, where, at the end of the cycle, the water once again absorbs the ammonia gas and the process is repeated, thus the name, ammonia-absorption cycle.  When on LP, a propane burner is used in the "heat" area of the unit and when operated on 110vac, an electrical heating coil is used to accomplish the same thing.  The fact that your unit works on LP means the refrigeration cycle is OK...what is happening is that your 110vac heater is NOT working for reasons cited by Gary and John.

If you do not trust your skills, find a friend with a voltmeter who knows how to use it and go "hunting."  You've already checked the outlet, next I'd check to see if there were any fuses on the control board of the fridge and make sure they are good.  Next, I'd see if their is any voltage going to the  heating coil.  To do so, and to facilitate the next measurement, I'd unhook one end of the heating coil from the circuit board or wherever it is attached and then measure voltage across the two points where the coil is normally attached.  You should see considerable voltage there.  If the reading is zero, I'd say you have a circuit board problem.  This could be as simple as a broken wire in the power cord, or it may indicate a failed board.  If the reading is close to 110, then I'd say you have a heating coil problem, but you can check this by now measuring the resistance (ohms) from one end of the heating coil to the other end that you disconnected.  This should be a low reading, but it should not be an "open" reading.  If it is open, then your heating coil is shot.

If your unit has some age on it, look for dirty corroded connections as well.  Good luck and keep us informed!

I'd almost bet the small glass-type fuse in the control box for 120v volt or AC has gone. Simply open the black control box in the back of the fridge and check each side of the fuse for 120V using a voltmeter as stated by tennsmith above. Each fuse should be clearly identified on the diagram there. Check also for corroded connections both at the wire connection terminal strip and the fuse holder.

tested with the voltmeter .... got an open circuit - element is shot.  Have a new one enroute, will reinstall and assume that everything will run smoothly again.  Thanks to all for so many replies and lots of information !!

Good luck with the repair!