One other thing I forgot to mention. Does it behave the same on both gas and electricity? Gas is the better heat source for the unit and as such it will typically perform better on gas. If it happens to work better on electricity, then the problem may well be that trash has gotten in to the orifice located between the gas valve and the burner. I have seen this in quite a few cases. It only takes the most minute piece of trash to cause issues. The orifice is brass and removable. It has to be removed to check and verify that no trash is present. A small wire or needle can be used to clean out the opening.
If it runs worse on gas, then the burner itself also should be checked. I have seen these become clogged with rust which forms due to the fact that the very act of burning propane produces water vapor. The burner is a elongated affair with slits cut across the surface. It can be cleaned or replaced. The flue/chimney itself should also be checked to verify that spiders or dirt daubers have not built nests in the flue. Anything that upsets the convection flow of heat in the cooling unit will have a dramatic impact on the ability of the unit to cool, especially in the lower section.
Also, you should have the gas pressure at the fridge checked(while the unit is running) to ensure that the propane regulator is functioning properly. If the pressure is not holding to the minimum spec of the fridge that will kill its performance on GAS. These things can fail regardless of age. For years Airstream used Fisher regulators which were SUPER reliable, but Fisher is no longer making regulators for RV use so Airstream has switched to Marshal units. Not an expensive item to replace (assuming a Marshal unit). The Fisher unit on my 1999 34 Limited still works perfectly. I did pull it down to clean and inspect it as the chemical added as an odorant to propane can collect in the regulator over time, but other a slight accumulation of the chemical, it was in excellent shape.
The fact that the unit freezes fine in the upper section, but not in the lower section pretty much clears the thermistor (clipped to one of the outer cooling vanes in the lower section). The way the unit operates is to regulate the temp in the lower unit to a temp slightly above freezing while allowing the upper unit to drop as cold is the ambient temps and the internal heat load will allow. The the thermistor was malfunctioning you would either be seeing freezing conditions in the lower unit (obviously not the situation) OR the upper unit would not be holding below freezing.
Adding a battery operated cooling fan helps to circulate air in the lower unit, but given that you have stated that the lower unit will not cool below 63 degrees pretty much indicates that circulating the air will really not improve things.
As Daisy mentioned adding an fan under the roof vent cap for the fridge to pull the hot air out of the cavity behind the fridge can improve performance, but again, what you are describing is pretty severe and likely not a result of poor ventilation behind the unit. Also, unless you are in Arizona, you are likely not yet experiencing exceptionally hot outside temps that could impact performance, but again, even those typically only result in lower unit temps in the upper 40s and you are experiencing mid 60 temps.
The bottom line is that either you are experiencing insufficient flow of the ammonia/hydrogen/water refrigerant (not enough heat at the boiler or a internal plug restricting the flow of the refrigerant), or inadequate amount of the refrigerant (ie a leak). As I stated previously, burping occasionally does wonders, but my experience is that it is a temporary fix at best. Dometic always paid us to try burping a still-in-warranty unit that was not cooling, but in every case, it was only a matter of time before the unit stopped cooling as it should.
david t
On Apr 11, 2012, at 6:21 PM, Hunter Hampton wrote:
> On 4/11/2012 6:00 PM, D Welch wrote:
> > But if any of the symptoms David mentioned, ammonia smell, yellowy
> > powder, are present, it's time for a new cooling unit, alas.
> I had a new cooling unit put in mine when the yellowy power made an
> appearance )c:
>
> Cost was about 650.00..... worth every penny since buying a new fridge
> meant twice the money and remodeling the cabinet so it would fit.
>
> Hunter
>
>
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