I bought a couple of new headlight bulbs for the Focus, though I bought 100W rather than the 55W than was already installed, someone has said this will cause overheating problems in the headlamp unit and perhaps some wiring issues - has anyone any experience of this?
I never attempted I thing like that, but it is quite obvious doubling the power also the heating and the current shall be doubled. Overheating is possible overall when you are idle in a row or during warmer days, but problems to the cabling are for sure with a severe risk of fire.
As previous posts have said a 100w bulb uses significantly more current than a 55w one given the voltage stays constant. However what you will find is, because the wiring is very thin the voltage drop on the cable supplying the bulb is a lot greater.
Hence the voltage supplied to the actual bulb is less (because of the greater voltage drop). This in turn makes the light output significantly less than the 100w rating of the bulb. A slight drop in voltage makes a BIG difference in light output.
Other problems would probably be blown fuses, melting cable/bulb connector etc.
The only way to run 100w bulbs correctly is to rewire the circuit with correct size cable, through a correctly rated relay via a correctly rated fuse from the battery or some other low impedance supply point. Then use the existing cable supplying the bulb to switch the relay coil circuit.
A final problem may be heat on the plastic headlight lens cover !
Hope this helps - Mike
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