Sick Of It! Time to update my SC Fusebox

[OsoMoore]

Thanks for the excellent pictures, Algernon. I will see about updating like that. Do you have info on where you bought the relays and relay mount boxes?

Related question - My original fuses were 8 and 15 amp (among others). I the nearest ATO for those values are 7.5 and 16 amp. Should I be concerned about this?

[Algernon]

Originally Posted by OsoMoore

Thanks for the excellent pictures, Algernon. I will see about updating like that. Do you have info on where you bought the relays and relay mount boxes?

Related question - My original fuses were 8 and 15 amp (among others). I the nearest ATO for those values are 7.5 and 16 amp. Should I be concerned about this?

Fuses do not have real specifications, only typical ratings - and they are very lax relative to other components.
A new normal opening medium acting fuse will typically never blow at 100% current!
At 125% of its rating (say12.5A for a 10A fuse) it will typically blow within an hour!
At 200% rating, expect typically 1 to 10 seconds!
"Slow-blow" fuses at 200% rating typically blow between 10 and 100seconds.
"Fast blow" fuse at 200% rating typically blow between 0.1 and 1 second.
Bear in mind that a factor of 10 (!) either way in actual time to blow is not unusual for a randomly selected fuse out of a batch. So that in real life an actual slow blow might blow quicker than a medium blow fuse. Fuses do not usually come with a blow-time guarantee!
After years of service and consequent heat cycling, fuses change, becoming more brittle, etc., and may randomly blow at currents they have successfully passed for years, even if this is below their nominal rating. This is referred to as a nuisance blow, and usually is cured with a new fuse of identical rating, and is no cause for concern.
Fuse manufacturers usually recommend running a fuse at not more than about 75% rating (7.5A through a 10A fuse)
Add all these variables together and you can see that changing a 7.5A fuse for an 8A fuse should not be a concern. Fuses really only protect from gross overloads, like a dead short. For stalled motors, poor contact connections and the like, where current does not rise dramatically, often the device itself or the wiring will burn up before the fuse goes. ATO fuse (and holder) characteristics are so much better than the originals it is a most worthwhile improvement. But its still worth carrying a few extra fuses and a fire extinguisher!!

[Algernon]

Originally Posted by OsoMoore

Thanks for the excellent pictures, Algernon. I will see about updating like that. Do you have info on where you bought the relays and relay mount boxes?

Related question - My original fuses were 8 and 15 amp (among others). I the nearest ATO for those values are 7.5 and 16 amp. Should I be concerned about this?

The relays are 911-615-103-01 from our host, and contain an ATO fuse and a removable metal fixing bracket.
I folded the brackets so that I could screw them to a piece of Alum. bent to fit right next to the fuse box. Not really a mounting box!
The 4 power wires that go to the lights were removed from the fuse positions 5,6,7 and 8. I added quick-connects to the ends which easily reached the new relays without extra joins.
Relay sockets are available with wires already connected. However these already contain quick-connects built in, and still need connecting to the filament wires. Just one more set of connections to go wrong!
I always aim for the minimum number of (well made) joins, as electrical problems are an often un-necessary and always annoying element in these cars.

[allaircooled]

I also used 4 relays. I used this relay box I found and a matching fuse box. The fuse box is very limited and is maxed out already so I bought one of Fred's upgrade kits almost two years ago and still need to install it. I think I will keep the relay box though.

[Algernon]

Yes, that looks very hygienic! I'm guessing an earlier car, as there are not so many fuses. Relay box looks nice!
Where did it come from? I think it would take some modification to use the relays with built in fuse. Unless you could squeeze all the fuses into the ATO strip!!

[donporfi]

I was going to suggest to use relay sockets, but agree on less joints is better.
I found these relays and sockets.

[OsoMoore]

For reference's sake, here's how the blocks are ganged in back on an SC. Note that there is some additional ganging via a copper "jumper" on the front side.

[OsoMoore]

My inital fuse box update left the box cover unable to snap in place. This was because of the breakout cable for headlight relays a PO had installed. I moved the fuses into the box proper.



Here you can see two more fuse spots are now taken.



However I then discovered that the fuses stuck out too far for the box cover to clip on - probably about 1/3 of an inch. So I drilled a few little holes and reached the following compromise solution.

[Algernon]

Hi OsoMoore,
I am surprised your fuse box lid did not fit after converting to ATO's!
Mine snaps on (just) so I'm guessing the aluminum strip you added is thicker than it looks. Or maybe the screws from the back are not counter-sunk? That's a pity, but the good news is that the wing-nuts look better! When I did mine I was nervous that the lid would not fit, and plan B was to cut out the offending strip of the lid, and replace with acrylic fitted to the 'outside' surface. I was guessing that the extra clearance over the fuses to the acrylic would be enough. Also, replacing the fuses with 'indicator' fuses from HF would be a visible indication if any fuse blew, simply by looking at them through the 'window'.
I still think that makes sense - to be able to see the fuses are OK, but I never got round to carving up the lid as it fitted fine over the ATO fuses.

[MZ3 SBC]

i have found many solid posts about 79 911 SC but none are turbo specific. DOes anyone have a diagram they could share....

thanks

I have searched quite extensively...

[7783911]

had the same issue with the cover when i install Classik Panel..i like the "OSO" idea...

[7783911]

A clear cover would be a neat way to see the fuses. my Classik has a LED to indicate a blown fuse...

[RDM]

Originally Posted by MZ3 SBC

i have found many solid posts about 79 911 SC but none are turbo specific. DOes anyone have a diagram they could share....

thanks

I have searched quite extensively...

How is your turbo panel different from what you have seen here on the SCs?

[0cean]

Infinity box wiring is your answer.

[Eljimberino]

hi - where can one buy an affordable fuse box and relay solution, these days, please?

[jaudette3]

There's a new small company in Australia making some cool fuse panels. Called Adapt Motorsports, they are making panels with mini-blade fuses and LED indicator lights that indicate the fuse status. We're fans of theirs and are their North America distributor.





You will find information and pricing at the AC SHOP.

Before we signed up with Adapt we had one of our new product beta testers review one of their panels. You will find his Review Here. He liked it so much that he bought one for himself and one of his friends bought one.

This little company doesn't have much of a marketing budget as their funds go into product. We really like small innovative companies like Adapt and we're doing what we can to help them get established.

Thanks,
John

[Jonny H]

Innovation or imitation?

[shamrok]

Originally Posted by 0cean

Infinity box wiring is your answer.

Yesss. This car's wiring is so unnecessarily complicated and I want to do something like this or a solid state PDM. The only thing stopping me is being able to cleanly reconstruct a wiring diagram to troubleshoot it later.

[jaudette3]

Originally Posted by Jonny H

Innovation or imitation?

I had seen your great looking product before. I'm not keeping track, the boys in Australia may have copied you. Your prices appear to be about the same.

Cheers,
John