Fusing the Dash Lighting - How To
 

Several years ago, I skimmed a thread in the 911 forum about how the dash lighting, including the glove box light, the center console lighting (a/c controls, etc), is un-fused in all years of 911/930 models (at least until after 1989) and is responsible for many a dash fire that does tremendous damage if you're lucky and the car doesn't burn completely. It's hard to believe that such a high level of incompetence was continued with for so long, but it's true (Just ask Ken/gsxrken :D).

I thought this was ****ty, but never did anything about it until being inspired by Ken's misfortune - he is in the middle of removing the entire dash wiring harness, and all associated harness extensions (into the doors and such). So here is a bit of a "how to" for those that are interested.

First, I found a lot of information and excellent pictures of where the dash & control lighting originates, and where to fuse it, in the linked thread from 2003 -

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

The "what to do" is very easy to follow and seems to apply to most 911s (and did for my 1987 Turbo).

One thing worth mentioning is that some people in that thread suggest to remove the seat, the headlight switch (where the un-fused dash light wiring originates), or both, but I found that if you are not too big in the shoulders, gut or buttocks, you don't have to do either.

The wires that you are looking for are black and blue stripped. They are on post #58, which is impossible to see with the switch installed, but the colors are unmistakable and the post is on the far left side of the switch (as viewed from sitting in the driver's seat). There are two wires with female wire ends - they are bridged and share a singe male post on the switch. You can lay you head and arms under the dash and use a long, thin (different & the same as Paul) flatblade screwdriver to gently pry the bridged wires off of their shared switch post. They come off, and stay together due to the bridge. Pic is grainy but here it is (better pic in the above thread). Note that the headlight switch, complete with a dozen or so wires attached to it, is to the left of the un-attached wires.

http://forums.pelicanparts.com/uploa...1437541968.jpg

Incredibly, those two blue and black wires are the power source for all of the lighting that I mentioned previously, so all you have to do at this point is attach a male spade wire end to one end of a mini blade fuse holder (ATM) and a female to the other end - the female end attaches to the male switch post and the male end plugs into the bridged blue/black wire, and at that point, the whole system is now fused. Guys in that thread recommend a 3amp fuse, and that seems reasonable as some of the wire is little more than a thread (Paul ?!?!).

I completely covered the female wire end with heat-shrink (same as original). On the male end, I covered only the crimped area with heat-shrink, naturally, but after I tested it and was satisfied, used a large diameter piece of heat shrink over the whole junction (the two bridged female original ends on the blue/black wires and my new, male fuse end). You could use tape if you wanted to, of course.

http://forums.pelicanparts.com/uploa...1437542637.jpg

^^^
In that picture above, I've already attached the new, female end of the fuse link to the switch.

Here are pictures of how the fuse holder looks installed from beneath the dash (I used the phone's reverse lens feature as it's too tight to get under there with a camera and focus on anything).

http://forums.pelicanparts.com/uploa...1437542756.jpg

http://forums.pelicanparts.com/uploa...1437542785.jpg


As you can see above, there is plenty of room to neatly tuck the fuse holder out of sight, and it's not even too crammed in there to make it overly difficult to find if/when you need to.

http://forums.pelicanparts.com/uploa...1437542873.jpg

It's worth mentioning that it seems that many of the dash fires are caused by the glove box light, and after scoping it out, it's easy to see why.

The light fixture is simply held in place via friction with the hole in the dash (metal) that it presses into. It is a three position, rocker type fixture just like the left and right cabin lights are, and functions the same way. Due to this, the fixture is "hot" at all times, even with the key off and the glove box door closed, and for some idiotic reason, is un-fused (until you do this mod, buttofcourse). I checked all this out with my trusty multi-meter earlier today. Also, the wires are tiny, and the last six inches or so are not protected, other than their own insulation, from rubbing against the sharp, metal opening of the dash. I would be willing to bet Paul's ballsack that is precisely where Ken's fire originated since his car was not running at the time.

Here are some pictures. And even though the circuit is now fused, I decided to put some tiny-sized (aka - Paul sized), conduit over the unprotected sections of wire.

Edit - the glovebox light is not on the same circuit as the rest of the dash lighting, so the fuse mod here does not address that. Bob K. in the 911 forum pointed this out to me, I just confirmed that he was right and I was wrong. I'll investigate if it is fused otherwise, and report what I find.

http://forums.pelicanparts.com/uploa...1437543413.jpg
http://forums.pelicanparts.com/uploa...1437543434.jpg

I suppose it is common sense, but I forgot to mention that you need to disconnect the battery before doing any of this since some of the circuit is always hot, regardless of the key being on or not.

Also, I slung some wiseassery about Ken's misfortune since I know that he won't take offence, but the reality is, he has a major ass-whipper of a project on his hands, and replacing the dash harness is not a laugh inducing task what-so-ever. It is really hard to believe that Porsche did not follow even basic, electronics 101 when designing these machines.

Pretty nicely done.

I am stunned. I'd never expect a ripple fire of useful information like this from what appears to be a petite Texan, a rare breed for sure :) :) :)

Dammit, I need to do this.

I greatly appreciate you posting this.

Paul,

Nice write up and thanks for resurfacing this DIY. Invoking Paul's cherry bag was a powerful motivator.

In all seriousness, it's a good project, easy to justify to anyone who wonders "what is he doing out there" and a impactful preventative mod.

Nicely done and thanks!

Will

Ronnie,

I addressed you as Paul in my last post and apologize for directly the credit elsewhere. I must have really been affected by your reference to him.

You understand, of course, that this modification has served to move your car even farther from stock, further devaluing it in the process.

Thanks for the props, dudes.


Jesper, I'm big where it counts!


Will, by calling me "Paul", you have provided the actual Paul with the feeling that he has finally arrived. I'm sure he will express his gratitude in an appropriate manner!


Norm, stock can su@* my co*#!!! How do you like them thar poetry skills?!?!?! :D Butt seriously, I wondered the exact same thing; would one of the Q-tipper types actually reverse a mod such as this in the name of originality, thus putting the fire risk back in play?!

Thanks for posting your electrical updates, I just replaced my fuseblock in the frunk and will be doing the fuel pump, dash, updates in a couple of weeks this is very much a necessary update for these cars. electical wiring fires are very expensive, much better to risk some resale value a little over risking losing all to a serious fire IMO

Regards
Mike

The front AC condenser fan is also unfused in cars with factory AC. It's in a plastic housing right next to the gas tank... great. It's easy to splice an inline fuse into the 12 volt supply wire going to it.
I've seen the motors in those fans melt the plastic housing when they get old and seize up.
I think those motors are the same ones used in the plastic housing foot well heat blowers in the mid to late eightees cars.

^^^

For anybody wondering what Jim is referring to, here is the nose condenser fan; you can see the fuse holder that I added just the left of the motor housing.

Like he mentioned, there is a lot of reading in the 911 forum about cars that have been severely damaged when that un-fused motor seized and caught fire.

Porsche actually sells a plug and play fuse link for that, but when I saw that the price for it is over $50, before shipping, for something so ridiculously simple, and should have been part of the car in the first place, I said "Efffff that", and made my own (very easy to do).


Mike, I agree completely with your necessary wiring upgrades 'v' originality thoughts; and no problem about posting my updates & reviving old wiring info - glad to do it.

http://forums.pelicanparts.com/uploa...1437698610.jpg

Bolding mine but Señor Ronnie could be right. My power wires to the glove box are totally crispy all the way to where they go into the #$#&%$*!! under dash harness.
And the pigtail wire to the under hood light got so hot that the white male/female connector melted and could not be separated. I'm in the middle of yanking my entire harness over concerns that adjacent wires in the common bundle might have been damaged.

Be safe out there boys. https://lh3.googleusercontent.com/bE...E=w962-h721-no

Nice work, Ronnie.
Depending on what year 930 you're driving, if you've got footwell blowers, they're not fused either. Can't remember if the ventilation blower is fused. If you've got a power antenna......guess what?! NO FRIGGIN FUSE!
It appears Porsche, in the day, did not invest too heavily in EE's.

Thanks Dave. My footwell blowers are retro-fused, but both motors are seized and INOP. I've never fixed them (only pulled the blown fuses) since I only need a trickle of heat here in TexASS, so plenty even without the blowers. No power antena for my m/y, but need to check on the fused status of the fresh air blower.

I've also recently read the the front trunk light and the engine hatch light are both unfused, so will check into that soon and remedy if necessary.

Ken, you probably saw my large print edit noting that the glove box light is actually not part of the dash lighting circuit - I will find out what circuit it is on and see it yet another fuse link needs to be added to this joke of an electrical system. I hope you are forging ahead with your repair!

Sub'd

The front trunk light is on the same circuit as the glove box light. Makes sense because they are near by each other and they're both low wattage bulbs.

I cut the wire going to the front trunk light and put plastic covered male and female spade terminals on the wire so I can unplug them and turn off the trunk light while the hood is open.

I did that because I've had the hood open for hours at a time during daylight while working on things in there and if the trunk light is on the whole time it can run the battery down far enough where the car won't start.

European '88 Turbo Targa RHD.

Bonnet light,engine bay light,glove box light,courtesy light,radio and clock all fused via 5amp fuse in front fuse box on mine. Fuse no 4. Of course being Porsche,they're numbered from the right as you look down from above!
Still need the conduit in the glove box. And watch out for reversed polarity on the bonnet light. Common Porsche trick apparently!

I just fused the gauge lighting circuit on my 1988 Carrera this weekend. I went with a 2 Amp fuse and it seems to work so far. I'll be switching to LED gauge lights soon, so I assume 2 Amp rating will work well with their lower current draw.

I pulled the headlight switch and the task was very easy.

Unfortunately, my ashtray light remains unfused. I'll probably pull the bulb holder at some point and heat shrink the electrical connector. I'd still like to fuse that run of wire, or disconnect it as close to the fuse box as possible.