Hi All, this is my first post. I've search and also gone thru the entire SC forum and found nothing helpful. I search "reardefrost", "reardefog" and even simply "rear"!


I'm not much for electric stuf, so bear with me please. The rear defrost blows the fuse a few minutes after it is turned on. I change the fuse and same thing. I was going to simply go with a larger fuse but thought I should ask before. The car is being used by my girlfriend in northern Ontario. Rear defrost is NEEDED!


Going with a bigger fuse worked for the headlight on my bike. I went from a 50/60 watt to a 60/100 and have had no problems. Oh and the bike is a Kawi KRL650!!!





EDIT: Oops! It's a 2001 SC2 with 185000 kmEdited by: JonJon3281

I would not change the amperage of the fuse, that would override the protection the fuse offers the electrical wiring. You may melt the wires if you change to a higher amperage fuse. First check to see that the right amperage fuse is there. Your owners manual or flip side of the fuse cover should give the fuse rating for the rear window defrost. Next do a physical inspection of the electrical grid on the inside of the rear window. Sometimes these conduction lines can be damaged by aggressive cleaning or storage of objects on the rear window ledge. Check for loose connections at the grid. Finally, if the proper rating fuse is still melting after a few minutes, there must be a short somewhere in the circuit. Finding the short would require a wiring schematic of the rear window defroster. Unless the defrost switch itself is faulty.

Thanks Paulorlo! [img]smileys/smiley1.gif[/img]


I'm going to see her this weekend, guess I've got a few things to look for now.

The fact that the fuse does not blow immediately indicates that it is probably not a short, but instead a temperature dependent change in the resistance of the circuit, with the overall resistance dropping as the temp of the components in the circuit heat up from the current running through.

Could be the switch--it is a 2001 so it is a switch with a timer and is not necessary at zero resistance when in the "on" position. It may also be something strange like an alternate current path becoming available as the heating grid expands. Ensure there is nothing bridging across the grid from one line to another. Also ensure that the connectors at the sides are firmly attached and that there is no material near them that could be condcuting current through an alternate current path.

It is possible that the resistance of the grid itself is dropping too low, but I doubt it -- it is simple conductive heating and there's not a whole lot that can go wrong if all the grid lines are functional and intact.

Derf