Blown Fuses
Blown fuses are a definite sign of electrical problems. Often vehicle owners and mechanics alike will just go ahead and replace the fuse without looking further for the electrical problem in the circuit. The vehicle manufacturer sets the fuse amperage value at more than double what the circuit would normally carry. If a fuse blows for a given circuit, you can guarantee that even if the problem is intermittent that you will see this fuse problem again. 
Let me give you a specific example to prove my point and also something that you may find if you happen to have a Chevrolet vehicle from the mid-to early 90s. The government fleet that I work for mostly has late-model Chevrolet, Ford and Dodge pickup trucks. We also have about 40 older 1995 Chevrolet 1500 series pickups that only have about 40,000 miles on them and continue to operate in our fleet.
Automotive fuses keep blowingThe drivers of these vehicles were complaining about intermittent air conditioning operation. Upon inspection of the vehicle we were finding blown AC fuses.At first we were just popping in a new fuse and releasing the vehicle to continue its workday. But eventually we had to dig in and find out what was causing this problem.
Searching down an intermittent short can be extremely time-consuming and a real headache. I decided to take a look for some TSB's related to the blown A/C fuse problem. And low and behold I found one. The technical service bulletin explained that the AC wiring harness that runs on the underside of the dash board was known to chafe in two areas, causing an intermittent short circuit, which in turn was taking out the fuse. The service bulletin showed pictures of exactly where the wiring harnesses were chafing. The AC blower motor power wire was lightly rubbing up against the radio support bracket for the last 10 years. This eventually caused a bare spot on the wire insulation and the radio support bracket was grounded, causing a power to ground short circuit. The technical bulletin also described that the wire could rub against the ashtray support bracket as well. And we did see this on a few of our vehicles.
Blowing fuses the proper repair
There are several approved methods to repair this type of short circuit problem. In my case, I cut out the damaged part of the wire and just replaced it with but connectors on either side. A lot of people do not like to use but connectors, but I did use the specialized heat shrink connectors that do not allow moisture into the area. Another reason that this repair is okay, Is that this AC circuit is just a standard 12 volt automotive electrical circuit.
If this were a 5 Volt reference circuit for the computer than I would have used a different method of repair. The most important part of this repair was to relocate the air-conditioning wiring harness to a safe location so that it would not rub against any grounded objects meaning no more blown fuses. Two things to learn from this story are that if you have a blown fuse. Take a look at what circuit the fuse supplies, and then search for the electrical problem that caused it. The second lesson learned is that if you have a particular fuse that continues to blow this may be a failure that others are experiencing. Technical service bulletins can save you a lot of time and direct you to exactly what needs to be repaired.
This is an example of the automobile repair articles that I plan on providing for free that will keep you up-to-date with developing failure trends.
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