Monday, March 05, 2018

Bogus Fuse Attack

Bogus Fuse Attack

It was a moonless dark and lonely on the road that night, as I was driving along a country road far from city lights. I was pulling a small trailer behind me, and I was the only car on the winding road. It had just gotten dark and I had switched on my lights.

Then I started smelling something. It was the unmistakable smell of burnt plastic. From time to time I had smelled that smell before, and had been thinking it was coming from outside my car. Then, after I smelled that same burning plastic smell a few weeks before, and had pulled into a gas station to take a look around.

I was concerned about melting wires. I looked around and found nothing wrong. Now here was that smell again! Then it happened. My taillights wend out!

Oh goodness, here I was driving along an unlit country road with no taillights! I pulled into a church parking lot where there was a streetlight and got out to see if the trailer taillights were also out. They were.

Home was more than an hour away, and this meant that I would have to risk driving with no taillights. My mind raced. What about cops? I would have to drive right through a heavily patrolled city on my way home. Surely a cop would se that I had no taillights and I would get a ticket.

What about the risk of someone coming up from behind and running into me? Sure, the trailer had reflectors on it, but was it worth the risk?

Maybe it was just a blown fuse? Luckily I had a test light in the console and could easily determine if a fuse had blown. Holding a penlight in my teeth, I systematically touched the two test terminals on the top of each fuse. They all checked out! My heart sank.

This would mean that the problem had to be in the wiring somewhere. I knew that I had been pulling this very same trailer for over a decade, and it couldn’t be something new like a bad splice. There must have been a wire that rubbed through and shorted to ground somewhere.

But where? And how was I going to get home? I remembered the 4-way emergency flashers. Would they still work? I switched them on and Walla! They worked! I could safely drive home with the 4-way’s going and not get a ticket! That’s all that I would need to avoid the cops and not risk having a rear-end crash.

The next day I decided to tackle the problem. Starting at the connector for the trailer, I began tracking down the problem. Hmmm. There was no power at the flat-four trailer connector. There was no power in the wire where it went up to the fuse box. Hmmm.

I could picture the scenario which I’ve seen time and time again where the wire connector going into the fuse box itself would melt. That would explain the burnt plastic smell!

But before I detached the fuse box assembly, I decided to locate the fuse for the taillights and remove it. That way I could narrow down the problem to the wire feeding the fuse or the wire leading away from the fuse. I popped of the cover from the fuse box and something fell out.

I bent down to pick it up, and it was a blob of yellowish colored plastic. What’s this? How strange! Does this melted blob of plastic have something to do with the burned plastic smell? I examined the fuse panel and located the fuse for the taillights. It looked strange—there was no plastic on the fuse!

I extracted the remains of the fuse, and to my surprise, the fusible link was still intact. But there was clearly visible a charred mark on one of the legs of the fuse.

“This fuse got really hot, so hot that it melted its plastic casing—but it didn’t blow!” I reasoned.

Suddenly I remembered reading how there were bogus fuses flooding the market, fuses made in China. And the article said to beware, that these cheap copy-cat fuses didn’t provide any protection for the circuit like they were supposed to. The article had said that the fuse wouldn’t blow at the rating which they were marked.

Somewhere, sometime in the past someone had installed a cheap Chinese-made fuse in this slot on the panel. And since I wasn’t the original owner of this car, I would never know who had gone cheap and bought this fuse from a discount store.
I pulled the rest of the fuses from the fuse box and discovered another 20-Amp bogus fuse. I found a 20-Amp Buss and a 20-Amp Littlefuse for comparison. The difference was quite apparent.
That cheap fuse would could have caused an electrical fire.
Lessons learned:
1. Start troubleshooting an electrical problem at the fuses.
2. Never use off-name brand (Chinese) fuses.