Dash lighting fuse installation
 

I have installed a fuse to protect the dash lighting. The whole circuit that lights the counters, the heating controls, the electronic heating central between the seats, the switches for the rear defrost, the fog lights is not fused. I was afraid that a short there would cause extensive damage.
So for the general info, here a pictorial:

First, REMOVE the driver's seat. You'll thank me later, when your back does *not* kill you:

http://forums.pelicanparts.com/uploads/930dash01s.jpg

You can then easily rest on your back to look at the back of the headlight switch under the dash:


http://forums.pelicanparts.com/uploads/930dash04s.jpg

On that switch, identify the post 58A, it should have a lot of black/blue wires attached to it:

http://forums.pelicanparts.com/uploads/930dash05s.jpg

This is where the fuse will go. I bought a fuse holder and some 3A fuses:

http://forums.pelicanparts.com/uploads/930dash03s.jpg

A few crimps, welds, and shrink tube applications later:


http://forums.pelicanparts.com/uploads/930dash02s.jpg

All that is left is to put the fuse holder between the connection 58A and the black/blue wire bundle:

http://forums.pelicanparts.com/uploads/930dash08s.jpg

Tried, and it works. Not bad for a self confessed electrical moron (I actually understand quite quickly if you explain long enough).
GeorgeK

GeorgeK:
Nice job...
Just curious. When you say "It works"...do you mean the dash lights work with a fuse installed..and are "out" when the fuse is pulled ??
---Wil Ferch

Yes, that's it. Removing the fuse takes all the dash lighting out.
Actually, when I saw that the car did not catch fire right after an electrical modification of mine, I was quite relieved.
GeorgeK

GeorgeK:
One more thing GeorgeK...
This seems to be a jump-off from another thread, and you now confirmed ( thank you) pin # 58A. Steve Grosskemper from San Diego (?) region PCA first wrote this up in a tech article...but the pin number he used was incorrect, or was usable only for an earlier range of cars. Digging further, it appears from a review of my 85 Carrera wiring schematic, that such a fuse might only protect dashlights, but I thought it didn't protect fresh air blower area lighting ( two sources of power) and the climate control knob in the console. Can you confirm which car you did this on ( 76 or 83, as the pin # might be different)...and when you pull the fuse...what it all protects ??
---Wil Ferch

I did the same thing on my 69 except I used a circuit breaker from AutoZone. I did this while I was troubleshooting a short that turned out to be a bad fuel gauge. I just left the breaker on the circuit. On the 69 the dash is powered off pin 15 of the ignition switch. I installed the breaker after the switch and prior to the gauges then tucked it under the dash.

On this car ('83 930), the fuse protects all gauges, the heating/ventilation command, the fog and rear defrost switch lighting, the thermostatic command's lighting (between the seats). The ashtray lights is not covered by this fuse.
To be absolutely precise, I did *not* manage to look at the name of the terminal to which the lighting wires were attached (very little room there). I consulted the wiring schematics for the year 1983, and that indicated terminal 58A, and the black/blue wires.
What I *did* check was that the black/blue wires were the current for the dash et al lighting, and that once the fuse was in line, removing it cut the lighting, without affecting other electrical functions.
GeorgeK

I now checked the wiring diagram for the '77 Carrera and on that car too, the terminal 58A is the one feeding the dash lighting, and the heating panels. Can't check on my '76, it's still in the showroom waiting for an engine.
GeorgeK

It's a very clean installation. Would it be better to fuse the wire run earlier in the circuit -- closer to the batter? Where does the unfused wire originate anyway?

And does anybody know what you'd do on a '73?

Randy,
the other circuits coming off the switch are fused, only the dash lighting isn't. No use putting a fuse earlier in the path. Here the unfused circuit originates at the 58A terminal of the switch
GeorgeK

I'm confused... So technically the wire is fused but the fuse is such a high value that it won't blow if the wire gets accidently grounded?? Is that it?

Randy

In my case this fuse also powered the ignition circuit. When my fuel gauge died and caused the fues to blow, it killed power to the entire car. Hence I was left stranded. This was my reasoning for splitting the circuit in my car and adding the breaker. Keep in mind mine is a 69 and I do not know how different it is.

Randy , Here is the way I understand it:
Battery+--->Switch--->different circuits commanded by the switch, all of which ARE fused, except the one that brings current to light the dash. Hence the recommended installation.
GeorgeK

this project is a home run.. the pics relax the beginner.. the lugg. comp light is also on this circut.. solder the wires to the connector.. without the fuse it's a fire waiting to happen/maybe.. George used the proper 3amp fuse..

I've been insisting that my brother do this install on his'88.. his mechanic said he never heard of this install.
you gotta love Pelican.........

So this & the headlight relay are the reccommended electrical updates?!

Yes, they are the 2 most "dangerous" electrical places in the car.
For the 930 owners, there is another, more bothersome than dangerous: The second fuel pump, in front of the LR wheel is wire in series with the first under the tank, which loads the relay. Often in hot summer days, the relay gives up, stranding the car. The solution there is to rewire the 2nd fuel pump from the same command, with another relay and new wires.
But this only goes for cars with 2 fuel pumps (930 up to 1989, and maybe more modern ones?)
GeorgeK

Chris.. I don't know what they recommend.. IMO, the 911 wireing sucks... I wouldn't be alarmed if some circuts would only blow a fuse.. but when they are the reason that my 911 is burnt toast, that scares me..

and "the headlight relay" project... one is better than nothing, again to prevent toasted circuts.. 4 is the safest, IMO.. I use 2 75amp relays and new wires on big bulbs.. and another back-up ground strap from the starter case mounting bolt to the drivers tranny mount bolt is not a bad idea.. I got a pic of that if you want to cast the eyeball..

it's great that you take this stuff seriously.. and the projects are easy to do.. and it's a clean finger nail job................Ron

"it's great that you take this stuff seriously.. "

I guess you have to- no brainer.

I have noticed how hot a yellow wire at the back of the light switch gets when turned on. Can't be good!

Thanks for the info guys!

the circut was designed years ago when stock bulbs were less than 65/55w.. and had never been upgraded.......Ron

"Randy , Here is the way I understand it:
Battery+--->Switch--->different circuits commanded by the switch, all of which ARE fused, except the one that brings current to light the dash."

- Yow! There's awire that runs all the way to the switch w/o going thru the fuse box? Who designed this thing? Excellence was Expected but Not Always Achieved.

Glascow:
There are many more electrical areas..Porsche does a really poor job in this category.
- For A/c cars....add the 7.5A fuse kit for the front condenser fan. Another fire hazard.
- add headlight relays, as mentioned
- add upgraded relay with external 16A fuse in smugglers box ( A/c system)...late 70's to late 80's cars.
- oddly *all* relays that Porsche uses ( ex: foglight relay) is fused only on the power side...not on the control side. Quick wire switcheroo will fix this.
- fuse box disaster. Design uses riveted construction of fuse holders that may get loose over the years. At some point in time, take box out, re-tighten or solder the rivet connections. Some of these have "bus-bar" connections that jumper incoming points on the fusebox. Or use external wire jumpers. Best to add external wire jumpers *everywhere* there is a bus connection with no external jumper wire to begin with. This would end up being a duplicate, parallel circuit.
- 930 A/c system gangs too many loads into too few circuits. Steve Grosskemper ( again) ....or was it John Rice..offers suggestions on how to add more fuses to separate these loads and have the wires run cooler. I think this article resides somewhere in the Pelican Tech Article section.
- no headlight relays ( as mentioned)
- other interior lights are still not fused with this mod ( cig lighter...fresh air panel).

I could go on....but I'm getting ill again thinking about all this...and all the work ahead of me to remedy these "excellence expected but not achieved" designs. What did Porsche do?..hire apprentice electrical designers??


- Wil Ferch