Question: My car keeps blowing fuses. Should I install
a larger fuse?
Answer: Not unless you are willing to risk electrical
damage or a fire! A fuse is a protection device that is designed
to blow if the amp load in a circuit exceeds the "safe"
limit for that circuit. Fuses are built with a specific amp rating
which is marked on the fuse. The wiring and design load of the
circuit dictates the size of fuse that's required to protect the
circuit. Circuits that draw a lot of power need fuses with high
amp ratings (20 or 30 amps) while those that use minimal power
require smaller fuses (5 to 15 amps).
When the current in a circuit exceeds the normal limit for
whatever reason, the metal element in the fuse melts and opens
the circuit stopping the flow of current. A short, for example,
causes a runaway electrical current. If not stopped, wires can
start to melt and things can catch on fire. So respect the amp
ratings specified for fuses (which can usually be found in your
vehicle owners manual, on the fuse block itself or a fuse block
reference decal).
What happens if you install a fuse with the wrong amp rating?
If you install a 20 amp fuse in a circuit designed for 10 amps,
you're asking for trouble. A difference of 10 amps might not
sound like much, but it may be enough to fry a sensitive electronic
component or to overheat wires to the point where the insulation
may start to melt.
WARNING: Under no circumstances should you ever bypass or
eliminate a fuse. No electrical circuit should ever be operated
without fuse protection. This is extremely dangerous, especially
if you've had problems with a fuse blowing before.
If a fuse keeps blowing, it usually means something is amiss
in the circuit. The wiring should be checked along with the components
in the circuit to determine if there's a short or other problem.
The fuse for the windshield wiper circuit, for example, may
blow if ice or debris builds up in the cowl areas and interferes
with the movement of the wiper arms. If a fuse blows in a motor
circuit (heater blower motor, cooling fan motor, power seat or
window, electric fuel pump, etc.), it often indicates a shorted
motor. If a fuse in a light circuit blows, look for wiring or
connector shorts. Adding driving lights may also overtax the
headlight circuit unless a separate circuit is provided for the
driving lights. An A/C fuse will blow if the system is low on
refrigerant and is working unusually hard, or if the compressor
is hanging up. Stereo systems with high amp boosters should also
have their own electrical circuit with fuse protection to avoid
overloading the normal radio circuit.
