Alfa-less and lost.
AO Silver Member
Join Date: Jan 2003
Location: United Kingdom
Heated Rear-Window melting out fuses
Does anyone else have this happen? If I use my heated rear-window for a bit too long, especially if I forget to turn it off, I find the 30Amp fuse has melted and although the metal part of the fuse is still present and functioning, the fuse has got so hot that it melts the green plastic and it falls into the footwell.
Now this is not a great problem in that it is easy to pull the fuse wire with a pair of pliers and replace with yet another new one, or you can simply leave it be as the fuse appears to be functioning ok, but I wondered if anyone could help with a solution. Clearly there is too much current going through it (not far off 30Amp) and it is getting too hot at the fuse. If I put a resistor in the circuit somewhere would it simply reduce the current drain and stop the problem, or am I likely to just move the problem to something else?
I'm trying to remember basic physics, but I figure that if the 12v circuit is carrying upto 30A then the heated rear-window circuit is consuming upto 360W. Does it follow that the whole circuit has a resistance of 0.4Ohm? So if I got a resistor of 0.2Ohm in series with the heated rear-window circuit I would reduce the current going through it to 20A?
Of course doing this would mean that the heated rear-window would only consume 240W but would heat the window less effectively and would take longer to clear condensation from the window, so I may get more problems because the heated rear-window would be on for longer. Also, where can I get a 0.2Ohm resistor from? And if I pass even 20A through the 0.2Ohm resistor is this resistor likely to get very hot itself?