Fuse Panel Swap - ATC Done under $35 total
 

Hello Folks,

I had an issue with my brake lights which finally turned my attention to the ancient fuse panel. My 911 is of the 1974 flavor but this method should work for other years as well.

I hate the old canister fuses and dreaded electrical gremlins that would inevitably greet me at an inopportune time. Fortunately it was while I was taking the car out of winter storage rather than sitting at a stoplight with a soccer mom texting her way up behind me at 55mph.

If you're reading this then you know the same dread of ancient electrical systems that haunted me. I also know there are a lot of options in the market place with some very well thought out products but with price points that are a bit rich for those who are used to rolling their own. I've always been the DIY type - I find this saves a chunk of change often and it seems to have really delivered here. Enough text, here's pics of what shook out and how you can save a few hundred bucks to spend elsewhere:

Here's my ugly old fuse panel with gremlins:
http://i458.photobucket.com/albums/q...psswmdlsph.jpg

Although not pictured, I organized the wires by removing the top first and numbering with masking tape/marker each wire position (#1 Top, #2 top, #3 top, etc.) to ensure nothing would get mixed up.


As I mentioned financial benefit of this choice, I chose the Chief ATC blocks; if you buy the 6 position blocks then this is by far the most economical way. Don't be tempted to buy their larger blocks as the cost is much higher. The 6 unit blocks are under $1 per fuse slot ($5.80/6 positions) and expect ~$10 shipping in the CONUS. Here's one with the cover popped off:

http://i458.photobucket.com/albums/q...psot3o8wbb.jpg

http://i458.photobucket.com/albums/q...pst9nfd7id.jpg

The quantity of slots is determined simply by the number of 3 pack units riveted to a strip of aluminum. 4 x 6 packs is enough including extra to do the 3 fuse block in the engine bay and providing a spare 3 slot expansion bay in the frunk. ***DO NOT USE A LEVER ON THE SCREW HEAD OR YOU WILL BREAK THE SCREW, GUARANTEED.*** I used my bare hands on the torx bit to tighten things down and this is more than sufficient. Give each wire a tug to confirm it's secure before moving on.

To make these fit and not look funny with odd spacing, just pry the top off each 3 panel set and drill the rivets out on the back to remove the aluminum mounting panel. Then it's very simply mounting to the stock fuse panel bracket using a drill. I originally riveted the replacement Chief blocks to the Porsche bracket but quickly changed my mind. A rivet through plastic is a bad idea here... DON'T DO IT OR TRUST IT. I found the plastic block would easily work loose of even a properly sized rivet so I drilled all the rivets out (tuition) again and replaced with the trusty old friend, captain zip tie. The zip tie is far more secure looping around each 3 pack fuse block through the original hole and through the drilled holes in the Porsche bracket. The tie is out of sight once you snap the plastic top cover back on the backing panel. Snug as a bug in a rug.

http://i458.photobucket.com/albums/q...psw367wbhj.jpg

When connecting wires, I found that if multiple wires were connecting to the same position that they must be of the same gauge. If different gauge on the same position/screw then you must strip the wire back on the skinny side and fold it over itself to increase diameter to match the big fatty. Don't try stuffing a 10ga wire into the same position on one side of the screw with a 14ga on the other side as the 14ga will flop about in the breeze like a hotdog in a hallway... which is a fire risk.

I ran an extra 10ga wire from battery to the constant positions for convenience rather than running the jumpers between positions on the panel- this was personal preference for a bit more work/materials but made the job better in the end in my opinion. More power capacity to the fuse panel isn't a bad idea.

I ran an extra 3 position block to the frunk with constant power to the battery (positions 19, 20 and 21 pictured below). I have plans for this panel to include a fan for the oil cooler eventually... more to come on that in a future thread. Hopefully this helps someone else who dreads the fuse box area of their old 911. It's really not that bad of a job and a good piece of mind!

Finished project:
http://i458.photobucket.com/albums/q...pste09npjb.jpg

Total cost was under $35... I had shrink tube and other auto electrical materials on hand including extra fuses/wire. I feel much more confident with the new panel and fuses than the old. If you're on the fence, then don't wait... just do it.

Nice work.

Something that might be helpful for anyone else taking on a similar project. When I did something similar to one of my 911s, rather than using "jumper" wires between fuses, I used a thin strips of aluminium (with appropriate holes drilled in them) to make up "jumper" bars instead. I had to use my Dremel to remove a little plastic between the adjacent fuses so that the bars could be lay flat and be screwed down but, once done, it looked tidier. This also overcomes the issue of different size wires not being able to be used in any given hold down. Once the jumpers wires are removed from the equation, almost all fuses are single wire (or at least single size) connections.

I also made up a a plastic cover so that the screws (some of which are "hot" - ie always supplied with power) were no longer exposed to stuff floating around the trunk.

Finally, at the battery end - right next to the battery, I installed an extra block with a 4 separate 30 amp fuses. Two of these were to fuse the power supply cables that ran back to the ignition key and two were for the wires that ran to the main fuse box. Doing so ensures that there is a final fail safe for any short circuit.

Nice job. The fuel pump for 74 is not fuse (red/green) did you fuse your.

Looks nice. Can you provide a link to the supplier for the fuse blocks? Thanks.

Does the fuse box cover still fit over these? It does look like a great upgrade, and I think the idea of making "jumper" strips is a good one as well.

http://store.chiefenterprises.com

Part description is FP-ATO-S06

I wouldn't use aluminum as a jumper. Brass, or copper would be more appropriate to avoid corrosion. You can't do it with house wiring should be no different here.

Yes, the factory cover fits back on without any adjustment or interference.

Nice job

Thanks for the post and input. I thought of something similar closer to the battery but haven't yet decided which would be the best approach. The blocks used in this thread are rated at 30amps per slot; I would want a higher rate for the ignition switch wire and perhaps other feeds as well. I have it in mind for a future job.

Wow, stellar job. I love the idea, and the execution. And the part where you save all that money. That part I really like a lot.

Thanks to your info I just finished mine this morning! Much appreciated.

http://forums.pelicanparts.com/uploa...1437247232.jpg

http://forums.pelicanparts.com/uploa...1437247243.jpg

Wow, that looks really nice. Did you also use cable ties to attach the blocks?

Hello -

Thank you for the note. I was not aware the pump is without fuse - yikes. I'll trace with a meter and add a fuse for safety; perhaps at a new position where capacity exists. My experience with other Bosch EFI systems indicates 20AMP would be appropriate for the fuel pump circuit.

I'll share a photo of the fuel pump fuse once installed.

-Andrew

No, I actually drilled new mounting holes and Mig welded 4mm tee nuts to the back. I am using 4mm stainless cap screws for the attachment.

http://forums.pelicanparts.com/uploa...1437249108.jpg

The pair of 2 twelve gang buses just fit the stock fuse panel frame, but you need new mounting holes. You could just use nuts and bolts if you like but I wanted the extra project value and an excuse to break out the welder.

I wasn't crazy about the cable tie idea either... if it nags me too much then I'll go back to rivets similar to what Chief Industries/manufacturer has on there. I need to look for taller 1/8" aluminum rivet that holds better than the regular off the shelf stuff from the hardware store. They just don't grab well enough to inspire a lot of confidence... cable tie is out of sight and will hold for a millennia.

Here's a better look at the original rivets that these use to connect to the aluminum mounting strip:

http://i458.photobucket.com/albums/q...psvogla4pb.jpg

These are pretty snug- I would be fine leaving these be and mounting the strip with bolts as done above. I chose not to keep the aluminum strips in my project which is where alternative mounting methods came in.

OK, here's a dumb question - why can't you mount the blocks on a homebrew aluminum strip with screws and nuts, and then attach the aluminum strip to the fuse panel area?

For all that work just mount directly to the Porsche bracket I would think... what benefit is the aluminum strip going to do you?

I just took a few minutes and fused my fuel pump circuit as pors1968 recommended and snapped a few more pics as I put in another block. You can see the options to mount are going to be limited to strapping or rivets as a screw doesn't have any shoulder in here:

http://i458.photobucket.com/albums/q...psjzodz563.jpg

http://i458.photobucket.com/albums/q...ps2vaprco9.jpg

http://i458.photobucket.com/albums/q...pshdjyvr4k.jpg

Had a correct color match/gauge match wire length on hand so it won't confuse the next guy:
http://i458.photobucket.com/albums/q...psw9qoo19h.jpg

http://i458.photobucket.com/albums/q...psryq3aw4w.jpg

Cover fits in place perfectly:
http://i458.photobucket.com/albums/q...psiyk1hgy3.jpg

Careful. Remember that you need some 'headroom' in the current rating of the loom and fuse block to blow the fuse. I think the fattest Porsche wire (apart from starter/battery) is around 40 amps. E.g. A 40 amp fuse may not blow if in line with a 40amp wire.

For the same reason, you should not fit 30A fuses in fuse holders rated 30A.

Hi Johnny,

Exactly my concern and why these blocks aren't deployed as primaries off the battery. I'll add links there eventually but it's a different project, different scope.

My 70 has two parallel wires that run to the ignition key. I have each fused with 30amp and have had since 2008. Never had an issue.

Interesting. 30amp on a 10ga; I think you could go higher with a proper block but sounds unnecessary.

5 mins to swap the rear block. Done:

http://i458.photobucket.com/albums/q...psdfq7phrd.jpg

http://i458.photobucket.com/albums/q...psiqntes8m.jpg

Drove the car around tonight and notice a couple things.

1) Power windows go up and down faster.
2) New hi-torque starter cranks over even faster... perhaps just cleaned the contact on the battery terminal when I added one more 10ga to the fuse panel.

Things must have been a little resistance aged.

Beautiful!

One of those projects IMO that is inevitable.

Thanks - agreed, it is an upgrade that's low hanging fruit. If your wiring is in decent shape then the job is an afternoon of easy work.

Just curious how you managed to bus the 42 amp fat feed wire to both adjacent terminals without having to put three heavy gauge wires in one terminal?

Although the solution is cost effective, the linking of the terminals is a real pain. We went to a tracked circuit board for this very reason.

Just curious, what is the combined load capacity for each of the 3 fuse blocks? If it is not 60 amps or so you might be overloading them.

Hi Jonny,

Wire gangs and a second feed to the battery were part of my job pictured here. Why fuss with jumpers on the panel if you can gang and add wire as the harness terminates? I did use some jumpers where it would be a slight bit cleaner as you can see.
http://i458.photobucket.com/albums/q...psw9qoo19h.jpg

Example: 1 10ga wire feeds 4 fuse slots

Why not gang and make the 1 10ga wire divided at the termination point to 4 10ga (or smaller gauge where appropriate) wires to feed the 4 slots? Materials required are only shrink tube, solder, spare wire. Concourse might not take to this approach but then again, concourse wouldn't be swapping fuse panels out either.

Jonny - also want to state that your panel is also extremely well thought out and apparently very well engineered. I've been chewing through my toy budget each month with more than one summer car needing attention/repair so bargains are on the menu for awhile. I'm sure I'm not alone and wanted to share with those on a similar quest for the sensible over the sumptuous.

Hi Fred,

Love your panel solution - a tad more elegant than this DIY approach.


To answer your question, 90A per 3 fuse panel must be the total as each individual circuit is diverse and rated at 30A max:

"Specications:
Rating: 30A max per circuit
Recommended wire size: up to 10 gauge
Termination torque: 14 in lbs.
Materials: Fuse panel housing-thermoplastic
Screw and pressure plate-nickel plated steel
Terminals-nickel plated 110 copper"

Lapkritis,

I just wanted to bring it to folks attention that if you go down this route, the factory harness has to be cut and in some cases extra wire tails added to split the feed wires.

You make the project sound very easy but that assumes people have a good understanding of electrics, wire ratings and such. It also requires lots of patience, note making and attention to detail. Soldering a harness in situ with the annoyingly short Porsche wires isn't easy either. For those reason I think describing this job as 'low hanging fruit' is trivialising it somewhat!

I would say allow a whole weekend and be prepared to encounter foreign wires, PO modifications and other oddities. Even with our 'plug and play' panel, we still get plenty of calls for help.

A quick question for Jonny H, what did you do to eliminate/mitigate corrosion on the existing wire ends when doing your fuse panel swap? All of the original panels that I have looked at had a significant amount of corrosion at the ends of the wires. I had to cut each wire back about 10mm to get clean copper for the new connection.

Hmm, I don't recall cutting the OEM harness. I specifically would have mentioned that...as I am sensitive to the notion. I did skin the insulator back at the end of the wire to expose more stranded wire to allow an adequate amount of material to connect to. This didn't bother me because some wires were also a bit roughed with existing nicks/abrasions/heat damage/probe holes and were an eyesore/unsafe. Where I felt necessary I covered the existing insulator with shrink tube for a repair even if I wasn't extending/ganging on the end.

So with the harness uncut, I or anyone who has the skills to do the work could return this to OEM again by removing any wire gangs, and just adding shrink tube insulator where skinned for job. Rather than tossing my OEM fuse blocks, they went right in the bins that hold the CIS system that was removed for PMO carbs 24 years ago etc. The car is too far into hotrod to justify going back to OEM but previous owners and I have kept all parts thus far removed except for the steel removed for flares. Maybe someday, someone will think that to be a worthwhile endeavor.

I do appreciate the trivialising comment - you're probably spot on as I didn't go into the finest details. I expect nearly each car to be different and didn't think it would be useful to go into what my car needed. Aftermarket alarms, stereos, fog lights, cb radios, neon underglow, and more are likely to be wired in on someone's 911. Questions are bound to pop up during the job but fortunately we have the forum resource to assist each other such as the case with adding a fused link for the fuel pump popped up here.

I think what might help with expectations of the job is assigning it a scale rating. On a scale of 1 to 5 with 1 being easiest chassis electrical job (swapping bulb in interior light) and 5 being most difficult (rewiring entire chassis/harness r&r), I would give this a 2.

Tools/materials to have on hand before starting:

1) Photographs of your existing panels with an inventoried list of wire colors in each position.

2) Labels/white masking tape and permanent marker for labeling wires with position as you disconnect the OEM panel.

3) Soldering iron of at least 30watts.

4) Rosin core solder.

5) Shrink tube of various sizes.

6) Electrical tape

7) Heat shrink ring terminals for 10ga wire if you plan to add an additional feed to the panel.

8) Drill with 1/8" bit.

9) Torx bit for terminal screws.

10) Plastic cable straps/zip ties(smaller size).

The job itself is not a comfortable position to be working in. You'll be hunched over the fender or awkwardly in the frunk like a hen keeping her spare tire egg warm. Not every job is comfortable or easiest. It should be apparent to anyone that swapping a fuse panel in the front of a 911 is going to have inherent organizational skill requirements. If you don't label wires and expect to not need jumpers/gangs added then you're in for a rude awakening.

^ Spot on, especially the bit about the working position!


[p.s. All original Porsche wires have ferrules crimped on the end which is why I assumed you'd cut them but of course it could have been a PO who did that]

Well said..............
 

I agree with all the above. The working position for doing this job is a pain in the back! I figure on about 8 hours to install one of my panels. If you happen to have the fuel tank out, it does make the job a bit easier. Your solution for this panel replacement appears to be well thought out and executed. Nothing quite as satisfying as having a DIY project come out right. Or, as Hannibal Smith would have said, "I love it when a plan comes together!". One thing that I especially agree with is that each job is unique due to hacks done by previous owners. Before starting this job, you should know what each and every wire is for! And, label the wires as they are removed. That will at least give you a fighting chance to make it all correct!

I imagine someday, a young buck will be working on this 911 cursing me as a PO. :)

I had thoughts about mitigating contact corrosion. A quick wipe of dielectric grease on the naked strands before assembly under the screw would to the trick.

I have to ask if you're sure. None of my wires had ferrules. I did have to break the wax pen on most screws during the job leading me to believe there were none on the car in 1974.

Both my 69 and my 70 had no ferrules on the wire ends either.

When I replaced my fuseblock all of the wires had ferrules on them. I only had to remove one when I had to cut back on the fuel pump feed wire that was cooked.
The ferrules are of a size on some of the larger wires that may be very difficult to fit under the new fuseblock terminals.

Perhaps the ferrules were introduced in the mid seventies then? Pretty sure they were on a 1975 we supplied a panel for recently.

The ferrules on the larger wire feeds may have to be removed if you're going to use the Chief blocks.