cooling fan experts needed

[klm2500hd]

I'll try my best to explain everything-
This is on a 1984 944 n/a. Other than the following problem everything works as it should i.e. low speed works, fans turn on and shut off when they should, fans work with A/C turned on, etc.

-Plastic part of fuse for driver's side is melting, actual fuse portion stays intact fuse feels hot when fans are running

-Contacts in fuse block have been cleaned, not a resistance issue.
-Swapped out fan for known good fan and also a new fan, still happens

-Put original fan on passenger side, problem stays on driver's side, so that rules out the fans themselves.

-pulled fuse out, checked for continuity to ground, none there. wiggled full lenghth of wire harness while checking for continuity to see if it was happening when going over bumps, no continuity.

-With the fuse pulled when the fans are supposed to be on, via thermoswitch or A/C, I get continuity to ground on the fused side of the fuse block (not constant 12V side). Unplug the harness from the fan and I do not get continuity with ground. Which leads me back to think it's a fan problem, but I've already ruled that out.

I'm at a loss for what's happening here, any ideas?

[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?

[klm2500hd]

Funny you should reply, it was an old post of yours that made me clean the contacts in case corrosion was causing resistance . Looks like it's time to pull the fuse block to check the back side.

[klm2500hd]

Update, I think the grounding issue is just the meter reading ground through the fan motor. Under further diagnosis both fans do it. Put in a ceramic fuse, and all is good for a week, A/C on the whole time, so about 15 hours of fans running on high speed. Only pulling 7ish amps. Concluding at this point it's the cheap Autozone fuses. One of these is 16A (red) and one 15A (black one). Fuse box is solid, and wires do not get hot, only the fuse.

[nynor]

this would happen on my '83. i found that the fan motor itself was difficult to turn. your problem seems to be different.