In my career as an industrial electrician a day at work often had you working on sophisticated automation one moment and the next call might be to someone’s office where you would be expected to fix anything that used electricity, often a personal radio or toaster oven. On such calls I would often hear, “it was working fine until it started smoking”. One of my favorite responses was that once the “magic smoke” was let out of the box the appliance was basically toast and there probably wasn’t anything I could do to repair it.
On Friday I feared that my joke had come back to haunt me. When I took the motorhome to the RV Park in final preparation for the trip, I was surprised to find the refrigerator wouldn’t work. My initial checks confirmed I had both 120 volt AC and 12 volts DC connected to the frig. At the control circuit board I had power going in and nothing coming out, it appeared that it had lost it’s “magic smoke!”
Its mid day Friday, we’re supposed to begin our journey on Monday and I’m sure that none of the local RV repair guys is going to have the part I need, a few calls confirmed this. I found one online, in Oregon, called and had them ship it to me overnight air, which on a weekend means Monday.
Nothing more I could do so I returned to my condo and continued departure preparations.
That night as I often do I rehashed the problem; looking for anything I might have overlooked, two thoughts came to mind. When I reconnected the 12 volt wires did I reverse the polarity thereby frying the circuit board? (The frig had been removed for repair to the ice maker, see the ice maker repair posting) The second possibility was, did I truly have 12 volts at the frig. A digital voltmeter will sometimes read voltage when it’s not really there. An example would be a severely corroded connection that will resist the flow of current, or the inside of a blown fuse with trace carbon (smoke) bridging the contacts. In either of these conditions a digital meter could read the potential but it’s actually not useable voltage.
On Saturday morning it didn’t take me long to discover I was reading the voltage potential through a blown fuse. When all this happened on Friday my focus shifted from troubleshooting to parts acquisition and I didn’t complete the investigation.
The good news is the frig is working, we are still departing on Monday and I have a spare circuit board in case I ever need it. Oh and what caused the fuse to blow? I didn’t disconnect the power when removing the frig for the ice maker repair, I just removed the 12 volt wires from the junction block and let them hang. Apparently while I was jostling the frig out or back in the hot wire must have contacted ground and blew the fuse.
Is there a “Yen” message in this story? There probably is; but someone else will have to write that, the open road is calling and I just gotta go!
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