[mikepellegrini]

I had the same thing happen on my 83.

What I believe happened was that the fuse slot next door had been fried at one time (the holder was charred black) , and had damaged the fuse box.

The copper fuse holders are crimp connected to the wires coming into the fuse box. I believe the one fuse frying damaged the crimped connections to the holders on either side. Like you said, cleaning the holders themselves had no effect.

I solved the problem by installing new fuse holders and fuses. I wasn't able to find the Porsche fuse holders, so I used regular ATC fuse holders (which admittedly is kinda half-assed, but works. If I happen onto a good new fuse box with good connectors, I'll change it out).

I looked at the old-fan higher current-draw thing. I have three sets of fans and I measured the current draw in each of them. I found a low of around a little over 7 amps up to a high of just under 10 amps per fan. Six fans is a small sample (so I suppose there could still be really high current draw fans rolling around out there), but with the fuses and wiring rated at 16 amps, a 10 amp draw shouldn't be a problem.

If you have an infrared thermometer, pull down the fuse box and measure the temperature on the wires and on the fuse and fuse holders.

On mine, the wires themselves were relatively cool but the fuse holders (and fuses) got up as high as 180F. For me, that was conclusive.

Is there any evidence of damage to the adjoining fuse slots in your box?