High on the list of RVer nightmares is this one: Opening the refrigerator door to grab a “cool one” and coming back with something warm. An RV refrigerator that’s lost its cool just isn’t funny. While some fridge problems aren’t too difficult to fix, a bad cooling unit is decidedly a “bad news” situation. How do you know if your cooling unit is shot?
How it SHOULD work
An RV refrigerator’s cooling unit is the heart and soul of the fridge. If you take a peek in back by opening your outer access door you’ll see it. Stuck to the back of the fridge, it’s a network of coils and fins, and usually to the far right side, a boiler. How does this cooling unit do its magic trick of chilling your goodies?
The “blood” pulsing through your fridge’s veins is essentially a combination of ammonia and water. All the magic starts in the cooling unit boiler. The boiler heats up this liquid combination and separates the ammonia and water while pumping the respective fluids to their proper locations. The water flows through an absorber, and the ammonia to a condenser—in a gaseous state. In the condenser the ammonia “condenses” back into a liquid state. Then the liquid ammonia moves to an evaporator where it meets up with hydrogen gas, and hey presto! It becomes a very cold vapor. That chilly vapor moves on into cooling coils, chilling off the inside of your refrigerator box. That accomplished, it heads back to the absorber, where it meets up with water and mixes, and then heads back to the boiler for another round of the dance.
Cooling units gone bad
OK, that’s how it SHOULD work. But things can go wrong. The system is great, provided the refrigerator is kept relatively level, and that heat can clear out properly. But if off-level, or if for some reason insufficient cooling of the cooling unit itself doesn’t happen, the whole thing can overheat. In a worst-case scenario, the overheating can become so severe that a fire can break out, leading to (usually) disastrous consequences, as in “bye-bye RV.”
In a less spectacular situation, overheating of the cooling unit can cause it to clog up and stop cooling. Or a normally “closed system” can develop a leak. What can cause a leak? In addition to ammonia and water, cooling unit fluid includes a rust inhibitor, sodium chromate. If the system overheats, the inhibitor degrades, and corrosion of the internal system follows. Often the boiler wall thins out and can rupture. The high pressure ammonia-water combination is then released, and that’s the end of the cooling unit. That’s the best case scenario. If a boiler ruptures, a fire can be the unfortunate result. So how do you know if you have a bad cooling unit?
“Unholy trinity” of symptoms
There’s an “unholy trinity” of symptoms—and any one of them indicates that your RV cooling unit is headed to the graveyard.
- The nose knows. If you smell ammonia anywhere around your refrigerator, it’s bad news. Unless the cat tipped over a bottle of Parsons, if there’s an ammonia smell around your RV refrigerator it’s indicative of a cooling unit leak. No, sorry. You can’t “fix” a leaking cooling unit.
The infamous “yellow stain.” Open the inspection door and shine your flashlight around. If you see a yellow residue, you have a leak. Most often seen on the boiler, but can be found elsewhere, this residue is sodium chromate. That’s the corrosion inhibitor we talked about. If you see it outside of that closed system, it means the system isn’t closed anymore, and your cooling unit is “toast.”
- Gurgles—but no chill. RV refrigerators may make very little noise while operating. But if your reefer gurgles but doesn’t chill, it’s a pretty good sign your cooling unit is a goner. How so? The gurgle while not cooling is actually the sound of water boiling. There are only two causes for water boiling in a cooling unit. One is if the internal pressure has been lost, and reducing the boiling point of water in the system. Or if the ammonia in the system isn’t able to get back to the system’s holding tank, the boiler will quit pumping liquid, and the temperature will allow the water to boil. In either event, the damage is irreversible.
No resurrection of the dead (cooling unit)
Sad to say, a deceased cooling unit is just that: dead—and not resurrectable by the common mortal. Some “clever” RV sales outfits would now urge you to simply replace the entire refrigerator. Unless there’s something else wrong with your fridge, what may be a better alternative is to replace the cooling unit itself. It’s a job that can be done by a person with average mechanical skills, and doesn’t require specialized tools. And if your RV is a motorcoach with a skinny door, it’s probably the only alternative, unless you like popping out the windshield or a very large side window to maneuver the remove-and-replace scheme required to get a new refrigerator.
Avoid this mess
How much better to avoid the whole mess in the first place. We know some RVers curse “absorption” refrigerators, saying their technology just isn’t built to last. That doesn’t explain a whole crop of absorption reefers built for home use, still operating happily today. We know of many Servel brand refrigerators, built in the 1930s through the 1950s, that are still chilling out. The technology isn’t the problem, it’s the operational practices that create many fatal issues. Operated off-level, or in situations where they can’t throw off heat, RV absorption refrigerator cooling units are prone to failure. The difference in failure rates? Servel refrigerators weren’t stuffed into wheeled vehicles and, hence, didn’t suffer the indignity of being operated off-level. Kept on level, the cause of boiler failure is virtually eliminated.
Keep it level! We’ve written earlier about a device, Fridge Defend, that monitors your RV refrigerator and will prevent it from overheating. Keeping your cooling unit boiler from overheating will dramatically reduce the chances that you’ll face a dead cooling unit.