Dash lighting fuse installation

[911pcars]

I've got a couple of thoughts on this:

1.
Fusing the IP light circuit is a good idea. I don't recall the exact wiring path, but I believe it's battery > ign. switch > light switch > bulb circuit > ground or something like that. If so, the light switch also contains a potentiometer (variable resistor) circuit to provide full source voltage or to dim the instrument bulbs. That's two switches in the path; two potential locations for voltage drop (i.e. less voltage to the bulbs = dim bulbs). Perhaps a separate relay and switch can be introduced here, in parallel with the light switch to provide full source voltage to the light bulbs when dimming isn't needed. This add'l circuit might provide a little more umph to the wimpy bulbs since larger wattage versions are n/a.

2.
How many of you have a completely stock wiring circuit, untouched by a PO? You're fortunate if it is. How many mystery circuits and wiring kluges have you discovered (or performed) in your 911? Please do yourself and the next owner a favor by documenting on paper (or at least labeling the add-on wires) what the new purple and white wires are for. It'll be easier to troubleshoot a few years from now after you've forgotten how the alarm system (or equivalent circuit) was connected. The factory placed all the fuses in one central location for a reason. I think we should try to emulate/optimize/identify the location of these wiring components for someone's future sanity.

3.
JMHO,
Sherwood Lee
http://members.rennlist.org/911pcars

[Wil Ferch]

So far I've done exactly that for my stock 85 Carrera. Made Xerox copies of the factory wiring schematic and show all the upgrades, (even the front fusing of the A/C blower motor that was normally done in 88) in red line mods to this Xeroxed set.... in a big folder in a ziplock bag so it's in the car with me always. Good if I have to refer to it during some breakdown on a trip....and good for the next owner, or present day mechanic in case I don't work on the car.

PS---WHAT ABOUT MY QUESTIONS ??

--Wil

[Wil Ferch]

Guys:
I'm resurrecting this excellent thread to see if others encountered what I did.

I can't quite gain access to the switch area from behind..because there is a metal plate..aproximately triangular in shape in the under-corner of the dash... that is firmly attached that covers any possible way to get to the switch. The plate mounts a pull-cable for the gas tank or trunk release. I'm surprised I don't see the plate in George's posts ( see first underdash photo by George).

Do you then take out the switch from the frontside cockpit panel, instead?

---Wil Ferch

[fintstone]

Don't forget the footwell blower fuses were added in '88. If you have an earlier car with these, you should add this upgrade.

[GeorgeK]

Will, is your car a targa with lockable front hood release?

[Wil Ferch]

George:
No it's not a targa..it's an 85 USA-spec coupe. I'll look more closely soon to see if it has a lock...can't recall at the moment. But it's mounted as I said.

Flintstone...oh boy, you opened up a can of worms! Porsche did an abyssmal job of fusing our cars. Some required updates include:
-- the footwell blowers for early 80's cars...10A fuse for each. Not there on the early cars.
-- add the 7.5 Amp fuse for the front A/C condensor blower. Used from 87-88+
-- certainly add these dash fuses...no Porsche's had these from the factory.
-- replace the A/C relay with the upgrade from the 88+ cars mounted in the smuggler's box...it uses a goofy 16A external fuse instead of internal diode design of the earlier models..no one seems to understand the rationale for this, but there you are.
-- Look at Lee Rices' (?) Technical Articles here on Pelican in how to re-distribute the HEAVY electrical loads that Porsche ganged together...like combining the A/C and power seats...note how HOT the wires get and that even if the fuse doesn't blow...it seems to "distort" the fuse severely requiring frequent replacement??
-- adding relays to the stupid headlight circuits. The entire full-strength current flows throught the dinky steering column switch and begins to malfunction and fuse together..use relays ( like Marc Sucro's kit available from this board)...
-- I think Pelican member RoninLB even ahs something to say about the engine starting circuit to add a relay or such...along the rationale of the headlight circuits.

Get the picture?....add fuses EVERYWHERE...Porsche really missed the boat on electrical circuit design !!!!

---Wil Ferch

[Randy Webb]

"Porsche really missed the boat on electrical circuits..."

Excellence was expected...

but not always achived.

[Wil Ferch]

GeorgeK:
Finally got around to checking my USA spec car trunk release lever...it is a coupe with a locking "tee" handle. The "tee" is mounted on a plate as I stated before... that gets in the way.

Anybody else with USA spec cars done this mod yet?
---Wil Ferch

[RoninLB]

Originally posted by Wil Ferch
Anybody else with USA spec cars done this mod yet?

Hey Wil..

are you trying to install a dash light fuse ?

[Wil Ferch]

Yeah...using George's photos as a guide..I'm now finding the "tee" handle / bracket that interferes with simply *getting access* to the backside of the switch. Either I find a way around the obstacle...or maybe the switch can be pulled from the front ( wires still attached) ..and I work on it from there ?

A silly, simple question...I know ...but there you are !

---Wil

[RoninLB]

what I did is also pull the ignition switch and put in a new elec section.
If it has over 100k on it ? it's a weak link IMO.
Ignition sw contacts get toasted. It makes the whole job easier to pull both together. the elec part of the ign sw is about $40.. better to R&R now than to wait for a problem to possibly make you nuts later. The ign sw has a top screw that should be accessable with a long screwdriver from inside the trunk/thru the bulkhead/ thru a rubber plug; or it's a PIA to unscrew from underneith.

I also used a $10 marine store 3a resetable circuit breaker on the dash lite circut. it's about 1" X 1/4" X 1/2". It has a small pin attached to reset.

[Wil Ferch]

I think we're talking "light switch" ....

---Wil

[msailer]

On the two US spec 911, I am maintaining, I pull the light switch from the rear to gain access to the wiring.
Disconnect the ground wire on the battery first!
It does take a bit of wiggling to get the switch down to a workable location. After you have it out the first time, the next time is easier. You might have to cut a few wire ties and pull one of the bulkhead wire plug to make room.

[RoninLB]

Originally posted by Wil Ferch
I think we're talking "light switch" ....

yeah, I know.. I pulled the ign sw when I pulled the light sw.

[Wil Ferch]

bump...
OK...RoninLB says to also remove the ignition switch...I'm not about to do that at this time.
Again...the triangular piece makes it impossible to gain access from the rear. Can the pull-switch for lights be unscrewed from the front...and perhaps the switch ( and all the attached wires) can be pulled out toward the front???
This shoulda been an easy job !!...
---Wil

[dotorg]

I've dug through a lot of the wiring in my car, and frankly every last bit of it scares me.

I've looked at replacing the whole damn harness with a new one, but concours replacements are almost $2,000.

Right now my plan next winter is to rip all the wiring out of the car and replace it with a decidedly non-Porsche modern hot-rod wiring harness. $400 buys a 12 or 16 circuit harness with modern blade fuses, full relays on all the lights, etc.

May not be original, may not be what purists consider the right thing to do, but I won't have to worry about it any more.

[Wil Ferch]

To see what someone does for a particularly slick ATO fuse block replacement ...search on "Fred Cook".
--Wil

[RoninLB]

Originally posted by Wil Ferch
Again...the triangular piece makes it impossible to gain access from the rear. Can the pull-switch for lights be unscrewed from the front...and perhaps the switch ( and all the attached wires) can be pulled out toward the front???
This shoulda been an easy job !!...
---Wil

can you remove that piece ?
I think my pull-switch unscrewed.

[jbirkett]

This is an excellent thread. I am going to install relays for my headlights and also the fuse for the dash lights at the very least. I just picked up an '84 Carrera Turbo Look and everything was working. The other day I was on my way home setting at the trafic light enjoying the breeze coming in the window when I smelled smoke. Looked down and saw what looked like a gremlin smoking a cigar inside my steering column. The High Beam switch fused itself together, so turning off the headlights saved me. Luky for me it was daylight and I found a replacement at the local Pcar salvage yard.
All electrical wirings scare the dickens out of me. I've seen too many cars setting by the side of the road with brown or black interiors that weren't originally that color.

[charlesbahn]

Finally got around to some electical work to fuse the weak points:

1. Installed headlight relays
2. Installed 7.5 Amp fuse on front blower
3. Installed 10 Amp fuse on AC blower in smuggler's box
4. Installed 10 Amp fuses on each of the footwell blowers
5. Installed 3 Amp fuse on engine bay light (to prevent inattentive mechanic frying wiring harness)
6. Installed 3 Amp fuse for dash lighting per this thread.

I had the same problem as Will- not way to get to light switch. I found it is easily disconnected from the instrument panel and then drops out- easy to do without removing the seats:
The light switch is hiding behind here:


Unscrew the light knob, use a sharp tool to unscrew the plastic retaining nut:

The light switch assmebly is easily dropped out of the back of the dash, easy to work on:



Proceed as described earlier in this thread. Installation is simply reverse steps.

EDIT: edit to change 7.5 Amp fuse in smugglers box to 10 AMP. Immediately blew the 7.5, seems happy with the 10.