Don't oversize the fuse, an underdash wiring harness costs about 400 bucks to replace after it catches on fire, and your car costs what, 15 to 20 grand, your asking for a fire. Fix whatever the problem is. Get a resetable glass fuse replacement circuit breaker. They look like a little aluminum box, with two 90 degree fuse end caps on them. CAP, NAPA, Autozone sell them for about 2 bucks apeice. They snap right into the fuse panel and come in all the normal fuse ratings. When they blow, all you have to do is pull one leg out of the panel, then stick it right back in. Never buy another fuse again. I've got one on my dash light circuit, because I've got an intermittant fault in my headlight switch that was blowing the fuse every once and awhile when I turned the lights on or off. Works great.
The clutch is fed from the underdash circuit whenever the left slide switch switch is in position other than vent or heat. There is a switch on top of the inner heater box that is operated by the left most lever that energizes the clutch thru the low temperature switch on the fender side of the suitcase. Shouldn't be an issue becasue it's also energized in the 3 lower speeds and the fuse doesn't blow then.
If it's your underdash fuse, and it's only blowing when the fan is run on High speed then most likely it's your relay on top of the suitcase that is blowing the fuse. Check all the terminals and make sure there are no big dents in the relay that could be shorting out the internals. Could also be a short in the fan switch itself, as those things start get dirty and corroded with time, I had to clean mine up inside to get it to work a couple of years ago.
The only thing powered thru the heater circuit when the switch is in high is the relay on top of the suitcase (and the clutch). The relay in turn feeds the fan motor thru the 25 amp fuse in the wiring gutter, so if it was the motor then the 25 amp fuse would blow. Check your relay and underdash switch (real pain to get at)
See this thread on finding the 69 A/C relay.
[ 08-13-2004, 05:25 PM: Message edited by: Mark C ]