Unfused circuits
 

After reading a few posts about smoke and molten wires, I think I’m going to undertake a project to add fuses to the unfused circuits in my ‘73.

Is there a comprehensive list of all the stuff that’s unfused?

Great question. I would like to know also.

The instrument light cluster is one. There is an old thread here that is a great write-up. Super easy. You just install an inline fuse off the ignition switch with a 1 or 2A fuse. I’ll look for it and post in a few minutes.

Another one is the front A/C condenser fan. It’s on a fused circuit but it can still start a fire (right by the gas tank) if the motor seizes. Several people have lost their cars this way. Porsche added an inline fuse sometime in the late 80s after they realized this error. Another easy fix and Pelican also sells a plug and play kit if you don’t want to DIY.

Gauge light fuse fix:
http://forums.pelicanparts.com/porsche-911-technical-forum/105819-dash-lighting-fuse-installation.html

Pelican A/C condenser fan kit:
https://www.pelicanparts.com/More_Info/PEL61207700.htm?pn=PEL-612-077-00&bt=Y&fs=0&SVSVSI=801

Not a fuse thing but I like the ceramic plugs in the head light as a good upgrade. As is the headlight relay.

Post #6 here is a good one too

http://forums.pelicanparts.com/porsche-911-technical-forum/671858-smoke-under-dash.html

I couldnt find the thread where almost all the wires were melted behind the gauges that was scary! I seem to recall the cig lighter and glove compartment light are unfused aswell but they might be on the dash light circuit?

It's better practice, if possible, to locate fuses in a central or obvious location so it can be easily inspected should there be a malfunction years after your memory fades.

For example, the main fuse box.

Sherwood

Unfortunately the fuse Porsche added is too highly rated to blow before the AC blower wire melts. Hence the need to still add a lower rated fuse in this particular circuit.

be sure to check the wiring diagram for 1973 or 1973.5 whichever you have

most of the posts above relate to later cars

yours has all those unfused issues but maybe more

I'll be interested to see if there are others since I have a 1973.5

The basic issue is Porsche took the power from the battery, bypassed the fuseblock that is right next to it, and ran it into the dash to all the various controls, then they ran the wires back to the fuseblock, and then finally they ran them to the various loads.
It makes no sense. The fusible protection should be as close to the power source as possible.

It is the one part of the car that just drives me nuts.

Close! Actually the ash tray and the ventilation control panel lights are unfused. The lamp holder for the ash tray light doesn't take much "bumping" like when installing a new stereo unit for it to short.

The easy way is to add inline fuses from where they powered from the back of the light switch.

A follow up question...

Does anyone know what values the fuse should be for each of these circuits?

I’ve read 3A on the triple BK/BL dimmer lights. FWIW, I used the 2.5A inline fuse from the orig radio wiring for my ashtray light.

Heater lever is not fused and ignition hot lead

Is that on a different circuit than the dash lights?

yes different separate circuit. They are unfused on constantly hot (not switched).

Crimeny! What were these guys thinking?!?

Any idea where the “other end” of that connection terminates ?