How to check for a blown fuse
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There are two different methods for checking for blown fuses. The first one is simply to find the right fuse for the circuit or component in question and remove the fuse and check it visually.( There is usually a diagram on the inside of the fuse panel cover that explains which fuse is for which circuit/component.)
The secon
d method, which I prefer, is to use a test light and run through all the fuses one at a time. This way if there is any other blown fuses that you weren’t aware of you can find and replace them. If you don’t have a test light you can rig a simple one up with an automotive bulb and holder and some short lengths of wire (see picture). A test light at a Auto Parts store can cost as little as five dollars though and are a handy tool to have.
So where are the fuses located? There are two blocks of fuses in most cars, one located in the engine bay (which usually contains relay’s as well) and one inside the car, either behind a pull-out panel in the dash or under the dash around the foot-well area. Your owners manual will have a diagram or explanation of the exact location. Often there will be a ‘fuse puller’ in the fuse box for removing and fitting fuses.(arrow in picture)
I am using a vehicle with blade type fuses for this example however the test procedure is the same for the majority of fuse types found in modern motor cars.
The first step is to turn the ignition to the ‘on’ position. Next, find a good earth point for the aligator clip on the test light. In the picture I am using the negative terminal of the battery and any un-painted metal part in the engine bay will do. When checking the interior fuses, the head of a bolt will do as long as it screws into the vehicle frame or the door striker if the lead of the test light is long enough.
What we need to do is check both sides of the fuse where the metal protrudes slightly from the plastic casing. (see picture) If the test light lights up on both sides that fuse is ok. If the test light lights up on one side but not the other, that fuse is blown and needs replacing. While your are at it a check of all the other fuses is recommended.
A couple of things to consider when doing a fuse check. Any lighting circuits will not show any power unless the lights are switched on. So if you have a lighting problem switch the lights on first before checking for a blown fuse.
Fuses are there to protect electrical circuits and if the new fuse you put in blows there is a problem that needs to be seen to by an Auto Electrician.
Always replace a fuse with the same amperage rating as the one that came out. Blade fuses are colour coded as to their amp rating and glass type fuses have the amp rating stamped on one end, although a bit hard to read sometimes. Don’t substitute a different amp rating fuse for another, serious damage can be done or worse it may cause the wiring to melt and it may catch fire. Ouch!
Take care and be safe on the roads.
Craig
