GBC style fuse terminals, how many wires?

[andy_braselton]

I am wiring up an oil cooler fan on my 84 and have selected panel 3 fuse 1 to hook up to for the ignition, so that the fan goes off with the car. The bottom side of the terminal is the red wires there are already two there and the black one is on the top. Our hosts recommend in an article that I use 10 gauge wire. My question is how do I fit 3 wires in the bottom side of the terminal? Is this safe, 3 wires on the terminal? Can I also use the top terminal? I do have a relay hooked up. Is there a certain piggybacking technique to use, because I cant see anyway I am getting 2 14 gauge and one 10 gauge wire in that bottom terminal.

[timmy2]

10 gauge is way too big. What is the current draw of the fan?
16 AWG is good for 10 amps in a short 12 volt DC run under 7 feet.
Use a 14 gauge and you will be just fine.
https://www.wirebarn.com/Wire-Calculator-_ep_41.html

[andy_braselton]

The amp draw is 8. I’ll try the 14 Gauge.
Thanks for the help. Do you see any concern with have 3 wires on one fuse?

[timmy2]

If they fit, it will work. Compress the wire ends fairly flat and they should go in.
Porsche has fuse terminals with 3 wires in them for some years.

[fred cook]

The main thing you need to consider is the total current draw on that fuse. The number of wires is somewhat irrelevant.

[HaroldMHedge]

My 87 Porsche wiring diagram indicates that the fan power wiring is 1.5mm. I would recommend AWG 15 wiring.

Conversion table: American Wire Gauge [AWG] and metric wire standards

[andy_braselton]

I wired it up and turned it on. Lasted about 3 seconds and then a fuse blew. This is troublesome. I was told this fuse terminal has worked before for others. I will get some other fuses and diagnose. That being said anyone have idea of why? I am thinking too much amperage but I didn't have the sunroof and windows going at the same time so it should have only been 8 amps from the fan. The fan did kick on immediately with the ignition. I think it might have been because the switch was also on at the same time. Could this have caused a blown fuse?

[timmy2]

What size fuse blew?
is it rated at 25 amps?
How old was the fuse?

Maybe make a drawing of how you wired everything and post it up so we can analyze it.

[andy_braselton]

It was a 25 amp blue fuse. My guess is it could have been original. It was plastic not porcelain. I wondered if old age had something to do with it. Here is a photo of my wiring. Let me know if you need clarification.

[timmy2]

First glance, it looks like your switch is a dead short to Ground from the fuse when it closes.
That will blow the fuse every time.
I’ll take a better look tomorrow.

[timmy2]

Here you go.

Either wire the power from the fuse panel or the battery to the N.O. relay contacts at 87.
I have shown both options for you to choose from.

The switch to turn it on controls the relay coil picking up.
The way you had it was grounding the fuse output, causing it to blow.

Schematic for you:

[andy_braselton]

Thanks so much for your help. Grounding the switch out was complete stupidity on my part. I naively assumed on pole was ground and the other positive. I have a lot to learn about 12v wiring.

Thanks

[andy_braselton]

Many thanks. I spliced into the wire going from relay 86 to the fuse panel and CORRECTLY installed the switch. No more blown fuses and everything seems to be running great. Fan is very powerful.
Thanks for your help. I am clearly not a wiring guy. Once again this community has bailed me out.

[timmy2]

I’m happy you got it working.
Think of electric current like water in a hose. A switch is like an on/off valve in the line.