Today, while on the way home from a weekend at a music festival (my wife as in one of the instrument competitions) , I noticed the camper refrigerator wasn’t working properly.
The refrigerator operates on 12 volts DC, 120 volts AC or propane, and the DC part wasn’t working.
There was an error code being shown on the display, so I looked it up in the manual. The text for that error code was, “Unit not operating correctly”. Wow. That was not terribly helpful.
After checking the two fuses protecting the wiring going to the refrigerator and finding them okay, I searched around on the internet and found some wiring diagrams that included enough information for me to start figuring out the problem.
After about 20 minutes of checking, I decided it was a problem on the control circuit board (the ‘brains’). To access the control board, one must remove the refrigerator from the camper. That took about 90 minutes. It took another 30 minutes to remove the control board.
What did I find?
Well, it was quite annoying. There is a fuse on the control board that is inaccessible until one removes the circuit board. Worse yet, this fuse is smaller than the fuse in the easily accessible fuse panel. So, the hidden fuse will likely “blow” before the easily accessible fuse. This fuse had “blown”. But it was not due to a short circuit or an “overload”.
It was caused by a poor design.
The refrigerator’s 12 volt system uses 15 amps. The pieces that connect to the fuse on the control board have an absolute maximum rating of 15 amps. In the electronics world “absolute maximum rating” is something that must never be exceeded for any length of time, and it is best to operate things at less than “absolute maximum”.
It’s sort of like a car engine with “red line” on the tachometer. The “red line” is the absolute maximum rating and, obviously, one never keeps the engine at that speed for any length of time.
So, what happened. The connection, which was being used at “absolute maximum “, started to get hot. This caused the connection to become worse, which made the connection get even hotter…which caused the connection to get worse….and so on.
The fuse was charred and eventually got hot enough to melt inside of the fuse and the solder holding the fuse connections in place. The control board was also charred.
I reworked the fuse connections and replaced the fuse, so the refrigerator is working again on 12 volts, but I don’t think it will last very long.
I called a camper service/parts place to get the needed part ($250) and found out the manufacturer had extended the refrigerator warranty from the listed 1 year to 2 years. This camper is 20 months old. So, I put everything back together, kept the charred fuse and called to make a service appointment.
Had I known it was still under warranty, I would have just called for the service appointment.
I also found out the part is currently on backorder and is likely unavailable for the next 2-3 months. So, after they examine the unit and decide it really is bad, I’m making some modifications to the system so that the control board, even with the charring, will likely last for many years.
The control board will control a relay that I’m adding to the system. A relay is essentially a remote controlled switch that uses a small current to power an electromagnet in the relay and the electromagnet operates a switch capable of handling 30-40 amps of current. This relay needs about 0.1 amp from the control board, so the control board won’t be stressed. The relay will then do the “hard work” of switching the 15 amp current needed by the refrigerator, and since the relay is being used far below its ratings, it should last a very long time.
I paid $12 for the components.
Had the design used better parts to connect to the fuse (an extra 75 cents…I checked…..) or the $12 system I’m going to set up, this problem wouldn’t have happened. My guess is that the engineer knew this, but was told to minimize costs and build it “just good enough”…with just good enough being “lasts long enough to make it through the warranty before failing”.