Guys:
I'm resurrecting this ancient & excellent thread to see if anyone knows what these terminals look like on the early cars (say, a 1973.5)?

Mine has 2 different places that appear to have blue/black wires going in - one on the outer ring of terminal and one on the inner ring (yes, the terminals on my car are arranged in two concentric rings).

I don't see any #'s near the switch terminals, but then I have not gotten the magnifying glass out yet either - am hoping to avoid that...

I don't know if this helps but in my 1970 there was 2 black/blue wires both connected to terminal 58a. One is for dash lights and one is for ashtray. Both deserve to be fused.

thx - I may need to get out the ohm meter

Randy,

Looking at the electrical diagram: http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_1973_CIS_Part1.jpg

Part number 32 is the headlamp switch and instrument light dimmer. There are 3 wires coming off of the rheostat "terminal 58a": one red/black and two blue black. you will need to interecept all three of these and put the fuse between terminal 58a and these three wires.

thx, unfortunately I can't find that exact configuration on mine (!)

Randy,
Pull the black/blue wires off one connection and see if the dash lights go out. That would be the bundle to fuse. If both bundles light different parts of the dash, two fuses.

On my car, the red/black wire goes to illuminate the Hazard Flasher after going through a resistor to dim the lamp. Per the drawing, one of blue/black wires goes tothe instrument lights and the other is to illuminate the ash tray and heater control light on the tunnel.

The resistor being the light switch (rheostat or potentiometer). At the full bright switch setting, there should be full source voltage for the bulb circuit. If there's any voltage difference, try temporarily bypassing the switch and see if the panel bulbs become a tad brighter.

Sherwood

Dash lighting fuse installation
 

I recently completed this modification as well. I tried taking the seat out, but still had a hard time figuring out what I was looking at. Removing the left A/C vent gave me a much better view of what was going on and being able to get one hand under under the dash let me work from both sides of the light switch when it came time to reconnect the fuse terminal to the switch. http://img.tapatalk.com/d/14/07/25/7umu8eby.jpg

I'm resurrecting this this old but excellent thread with a question:

What size male spade and female terminals are required to be joined to the fuse holder??

I think it's the 14-16 gauge size. I believe they are the same as pretty much every other terminal in the electrical on this car.

Yes, they are 14-16 gauge.
More basic info here
http://forums.pelicanparts.com/porsche-911-technical-forum/838193-ok-fuse-all-3-wires-going-into-58a-dash-light-fuse-headlight-switch.html

Perfect! Thank you :D

Gentlemen,good evening. (If there are any ladies reading this,forgive me. You're honorary blokes!)
This thread,and another,"fusing the dashboard lights. How to," make scary reading. Thank you all for the info and recommendations. Just thought I'd add my 2 pennies worth.
The car is an '88 939 Turbo Targa and RHD.
To fuse the dash lights I found it easiest to remove the light switch from the dashboard. Pop the cover and remove the retaining nut,then undo the retaining ring. More than enough play in the wiring to bring the switch into view below the dash.
I found that the interior courtesy lights in the cab,the light in the bonnet and the engine bay,the clock and the radio,and the glove box light are all on the same circuit protected by a 5 amp fuse in the bonnet fuse box. It's no 4 on mine,and being Porsche,it's numbered from the right as you look at it from above! Still needs the conduit for the glove box wiring but at least it's a relatively reasonably rated fuse.
Sadly,I was too late for the air con condenser blower. Dead as a dodo,with a blackened winding. Still,at least the wiring was intact! There are a few replacement options.
1)A Porsche fan. Complete with housing etc. Comes in at about £255,or $420.
2)APelican replacement motor.$195,or $85 for something of which there is no picture.
3)an uprated blower,fan and housing from RetroAir.com which comes in at $185.
I went for this last,so we shall see.
The footwell blowers were already fused with 10amp fuses,1 of which had blown with a seized fan. Freed this off and now works perfectly.

So far so good! Thank you all so much for your help

Dash fuse
 

Hi---can you tell me where the other wire goes once the wire is on 58A. Thank you.
Gary

The "other wire" plugs into the connector you removed from the 58a terminal.

Rahl

Thanks guys

It was a quick fix and took me 10 mins to install in a RHD, thanks for the help. Took me longer to find a 3 amp fuse :)

Just got around to fusing the interior light circuit a few days ago. Thanks to Charlesbahn's instruction to simply remove the light switch from the dash first, it was an easy job. No gymnastics required. My '88 did not have the protective plate at the bottom.
As additional information, I'd like to add that in order to remove the light switch knob, you must first pull it out which exposes a hole in the stem of the switch. To keep the switch from rotating while unscrewing the knob, you need to insert something (like a drill bit) thru those holes first. Simply turning the knob to try to unscrew it may damage the switch. Easy job; just remember to disconnect the battery first.

Just added this fuse while my seat was out. My car has the plate in the corner, so taking the switch out was necessary. Thanks for the tip about the hole in the switch shaft!

You're welcome. I came pretty close to breaking my switch before I figured that one out. :rolleyes:

Thanks to GeorgeK who started this thread way back in 2003 and all who have added their comments. I just finished adding a 3A mini fuse to this circuit. Way easier than I expected and well worth the investment in time for the piece of mind. As others have noted, after disconnecting battery and unscrewing plastic retaining nut, you can wiggle the switch out and down to gain very good access to the terminals. Only issue for me was that the retaining nut for the switch was cracked. Put it back together with some fiberglass resin and now back in business. One more electrical worry I’m crossing off my list.

I laughed when I saw this post come up. Funny...I have this bookmarked and on my schedule to add the 3A fuse today. Such an easy mod. I have recommended it many times (for over 20 years).

Sadly, I had the underdash smoke check and my headlight switch burned up Thursday night. Ka-ching...there goes a quick $400 (switch already ordered) and a few hours work double checking all related wiring for want of 10 minutes and a $10 part. Luckily, it appears (so far) there was no damage to my harness that I would have to repair...but found lots of "while I am in there things to do). Had this car for many years and had put off adding the fuse. Karma.

Let me recommend once again...do this easy mod.

Sorry for the bad luck. What bought the failure on?

Yeah I have had this thread saved for years and still haven't done it. I have what I need to do it just need to get it done. Maybe this will be a good thing to check off the list tomorrow. Sorry to hear your headlight switch burned up.

Not sure...but was messing with the heater/ventilation panel when it happened...so likely related (since the lights on the back of the panel are some of the unfused circuits). I had just replaced some bulbs and fixed the light that comes on when the fan comes on (previous owner had cut when they pulled the radio apparently). Everything was working and I was putting it all back.

Since I could not find the problem under the dash (other than a melted switch), I am also pulling the ventilation system (while I wait on a switch) to examine it better and so I can see the back of the firewall for damage to any wiring back there. I can get that perfect while I am in there.

Also karma...in my stash, I had a spare for every switch in the car but that one for the headlights... Guess I will put the Sucro headlight relays from my other car (found it looking through my parts for the headlight switch) in while I am at it.

Should have disconnected the battery...but had done that work many times without error. Since I had the frunk open, I did quickly grab a wrench and disconnect the positive terminal which may have reduced the damage. I usually leave it hooked up when fixing bullbs...as it saves a step or two when testing them. Bad call this time I guess.

Thanks! Oh well. Taught me a lesson (order priorities a bit better). At least I am very comfortable with fixing it...had a couple of these '74s...and have done most tasks at least once.

I'm also in the "I wish I had installed the fuse earlier" camp. I managed to short my dashboard lighting loom (I removed the steering column to put in new bearings and crushed one of the wires under a washer...), and let me tell you, it is a lot of work to open up the wiring loom to inspect and remove the burnt wire, and retape the loom. So in hindsight, 10$ and 5 minutes of work is a no brainer.

Bumping this one up for thoes who havn't done it and need to do it tomorrow. (Me).
Thankfully, no issues with my 79 coupe.

anyone know off hand what gauge the dash wiring is? 18 AWG?

Found it in the threa, 14-16 AWG

Doing some troubleshooting and had a related question:

How much voltage drop should I expect across wiring connected to gauges? e.g. Switches and related wiring from battery to gauge and then subsequently from the gauge to ground?

With the car running and battery voltage at the battery measured at 13.8V, I am only measuring ~12.6V from power to ground on my oil pressure and oil temp gauges, so I am dropping ~1.2V somewhere else in the circuit(s) and I'm wondering if that is normal.

Why I'm asking: I recently added a voltmeter to the aforementioned gauge and it's only displaying ~12.6V, which is obviously nowhere close to the true battery voltage. A loss of 1.2V on the rest of the circuit seems excessive, no?

Yes, 1.2v drop is excessive if that's on all circuits. Your volt gauge should show full voltage. If it doesn't, are you sure you connected it directly to a "hot" wire and a solid ground? Is the gauge accurate? (test it directly across the battery)

However, on your gauges, remember, the senders have resistance too. I don't know what that is offhand, but the voltage will be split proportionally across two resistances in series.

http://forums.pelicanparts.com/uploa...1678853855.jpg


I cant get this retaining nut to turn. Any suggestions??





1985 Carrera coupe M491

Take something like a needle nose pliers or a snap ring pliers and insert the ends into 2 of the holes and twist to unscrew. You’ll get better leverage that way. Once it starts to turn you’re fine, it’s just that initial breaking loose 35 years of dirt that you need to overcome.

Remove bezel with pick tool or snap ring pliers.
Remove washer with pick tool.
http://forums.pelicanparts.com/uploa...1578619815.jpg

Thank you. Ive been cranking on it w snap ring pliers.

They fit good, except Ive got 2 of the holes mildly damaged from turning so hard.
I sprayed around it w silicone & WD40, seperately. To no avail.

Its the initial 'breaking loose' that i require... ?

I too fused from 58a and added a LED supported dimmer since the OEM dimmer will not work with LEDs

Hmm, that seems odd. I wouldn't think it should take THAT much force to free it.

Maybe shock the snap ring pliers with a hammer it?

This rosette is still available from our host:
https://www.pelicanparts.com/More_Info/91161321307.htm?pn=911-613-213-07-OEM

So don't worry too much about damaging the one that's in there because you can still get it.

silly question...rotating the correct direction?

Fair question. Tho totally possible.
I once left a plastic cap on a battery post. Doh

Lefty loosey? im turning counter clockwise, as i view it.

Thanks