Mk2 Golf GTI lighting issues!

Dipped is sposed to go off when the mains are on are they seperate relays for each side or just the one ? if seperate check the relay if just the one check the earth but TBH if dipped is working i'd say the earth is ok, you sure you havn't just blown both the main and spot on the same side? out there but i've had it happen

you've lost me? do they work or not ?
dipped beam is a seperate elliment from main and they only work individualy, when dipped is on main is off and when main is on dipped is off so if the main beam isn't working when you turn it on the dipped will go off ? as it's sposed to?

Realy will i assume be in the fuse box with the other relays (long time sinse i worked on an early golf sorry) ( i assume it is an early golf ? )first pull the headlight connector of and clean the terminals and refit and try again, could be a simplee as a dodgy connection, you never know.

Sorry, I'm rubbish at explaining stuff
It has the factory fitted 4 headlight grill. Murran, according to the fuse diagram, Fuse 12 has blown. I'll check it first thing. I'm curse word with electrics and assumed that the high beams would be on one fuse, not one fuse per beam.
Fingers crossed. Thanks for the link to the fuse diagram mate, will be really useful!

if it has blown you need to find out why, as chance are it will blow again.
you'll have high resistance (ohms) somewhere in the main beam circuit on that side causing it to draw higher amps (as a consequence) than normal and so making the fuse blow.
corrosion in one of the plugs stiil plausible!!

in actual fact both a short and too much resistance in the circ. will blow the fuse..... as in a short (bypassing the electrical consumer) will increase current flow massivly blowing the fuse almost instantly.
high resistance causes heat in wiring by drawing amps thru the resistance this also blows fuses but often over time needing the time to heat up until the fuse cant take anymore .... in both cases it'll increase current flow and cause the fuse (the weak link) blow in the same way.
how can a decrease in current cause a fuse to blow?
example; a circuit isnt supposed to draw more than 6 amps.... the circuit has a 10 amp fuse.... more than 10amps draw and the fuse blows. decrease the draw.... say you fit a 5w bulb in it insted of a 21w bulb.... the circuit draws less amps! but if you fit, say a 60w bulb and the fuse blows cus your increasing resistance, you need a 20amp fuse in it now......
a head lamp bulb produces more heat than a number plate light bulb does it not?? thats cus theres more resistance, more amps required, more light produced.....

but if you short that circuit, the fuse blows cus theres no electrical consumer in the circuit... the draw of amps goes thru the roof! as there is no resistance back to earth and electricity takes the easyest path to earth, the electricity will flow unrestricted blowing the fuse, even if the fuse is big enough it'll melt the wires as the wires arnt large enough to take the current flowing with no consumer.
hence why a spark will jump out of a plug lead to the cyl head rather than jumping a spark plug gap, as its the easiest way to earth.

only an open circuit would decrease current flow and not blow a fuse as there is no circuit anymore to pass the electricity. so theres no amps flowing.

another example..... a glow plug circuit working draws 100 amps, 25 amps per glow plug.
the engine is not so good at cold starting... you stick your amps guage in the circuit and its only drawing 50 amps...... the fuse hasnt blown as its a 120amp fuse...... you know theres two glow plugs not working as it should be drawing 100 amps....
if you get your side cuts and snip the wire without shorting it out youve simply stopped all current flowing... fuse intact.
but if you short that circuit itll flow as many amps as the battery can as its unrestricted back to earth. itll blow that 120 amp fuse no problem, if it doesnt melt the wiring first.

Fair enough, yeah, I've got no argument with your last post at all:

Short circuit = low resistance = high current = blown fuse.
No circuit = no voltage = no current = intact fuse.

I'm just saying that increasing resistance won't blow a fuse, because you're decreasing current. The only exception being if you increase the resistance in the fuse its self. It's just a result of ohms law and the power equation.


Like I said, your initial point was a good one, so I'm on your side here , I was just wanting to make sure no miss-information was being posted, even if it was meant with the best intention, and ultimately caused no harm in this case.