Fuse Melt Down

The other day a Suburban came in the shop
that had the harness from the cigarette lighter
to the fuse box melted into one large glob of
wiring and plastic. The cause of the melt down
was pretty clear.  In the cigarette lighter socket
were several pennies jammed at the bottom. 

Nothing new, I see this sort of thing all the time,
but… why did this one burn all the way back to
the fuse box?  The owner told me later that day he had
been tinkering around with it for quite sometime trying to find
the problem himself.   His method of chasing down the elusive problem was to keep putting a fuse
into the fuse box until it either worked or smoke came out of the dash. 

I’ve seen this trial and error method before and the results are usually the same.  You’ll end up with a nice pile of melted together wires and a large repair bill for all your stabbing of new fuses into the fuse box.  But, this time… something was different.  Not only did he try the “stab a new fuse and look for smoke” method but he had gone down and bought a cheap box of fuses to try his little homemade test with.  

These cheap fuses don’t snap like normal fuses.  Their ratings are completely off the charts.  The little embossed number that indicates the amp. rating is entirely false.  With these fuses the small loop of connector material between the two terminal posts doesn't break when the current exceeds the amperage; no… they will actually melt the plastic housing before they break the electrical contact. (Or worse… not at all.)  Both edges of the fuse in this Suburban were melted down around the metal prongs that go into the fuse box. It was practically glued to the fusebox and it took the better part of the afternoon to free it from the box.  Just like in this car if there is a problem, such as pennies in the cigarette lighter, it will continue to flow current until something else melts apart. 

There’s a GM bulletin on this very subject that every tech should know about.  Bulletin #07-08-45-002, Doc ID 2009073

Here’s part of that bulletin.
Subject: Service Alert: Concerns with Aftermarket Fuses in GM Vehicles #07-08-45-002 - (09/05/2007)

Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks

Concerns with Harbor Freight Tools "Storehouse" Branded Blade Type Fuses
General Motors has become aware of a fuse recall by Harbor Freight Tools/Storehouse for a variety of aftermarket fuses. In two cases, these fuses have not provided protection for the wiring system of the vehicles they were customer installed in. Upon testing the 15 amp version, it was found that the fuse still would not "open" when shorted directly across the battery terminals.

How to Identify These Fuses

Packed in a 120 piece set, the fuse has a translucent, hard plastic, blue body with the amperage stamped into the top. There are no white painted numbers on the fuse to indicate amperage. There are no identifying marks on the fuse to tell who is making it. The fuses are known to be distributed by Harbor Freight Tools but there may be other marketers, and packaging of this style of fuse. It would be prudent to replace these fuses if found in a customer’s vehicle. Likewise, if wiring overheating is found you should check the fuse panel for the presence of this style of fuse.

Sure enough laying on the passenger front seat of this Suburban was a box of these very same fuses.  I informed the owner of what I knew about these cheap fuses and that I would definitely not use these for anything at all.

After getting all the repairs made I did go through and check out the rest of the fuse box for any more of these fuses.  Now that I know what to look for I’m constantly checking fuse boxes for these.  It will make my job a lot easier when I don’t have to look for a cause of a problem that is caused by another problem brought on by a tiny cheap part.  It’s amazing how much damage it can actually do.

I took one of these fuses out and put it in line with full battery voltage (negative on one side and positive on the other) it did blow, but not before melting the casing just as I had seen in the car.  Pretty scary to think there’s still a bunch of cars out on the road with these nasty little things in them.  (Job security I guess)
Not only did I find the original cause of the problem, (pennies in the cigarette socket) but the cause of the even bigger problem as to why the entire wiring harness melted back to the fuse box. Just another example of why cheap parts can get you into even more trouble than what you originally bargained for. 

                                                                                         click to enlarge photo

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