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Old 07-04-2017, 01:56 PM   #1
Robert Bergstrom
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72 fuse box upgrade needed?

I have a standard 1972 wire harness with glass fuses (w A/C). Do I need to upgrade my fuse box to the new modern panel in order to add power windows, Holley Sniper EFI 550-510 and an electric fuel pump (Holley 12-920)? The Sniper requires two wires (red and black) to the battery, blue to the fuel pump outlet +, yellow wire to the tach plug in on the HEI and a pink wire to a switched ignition +12v. The power window goes to a power wire close to fuse box and a ground.
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Old 07-05-2017, 10:40 AM   #2
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Re: 72 fuse box upgrade needed?

You will need relays for your windows and for your fuel pump. Unless I was rewiring the truck harness I would just fuse the power wires to the relays and to the EFI module.

A good option would be this. A power junction from the battery/alternator junction to each of the added loads you are installing. it uses fusible links. This one is from Mad Electric.

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Old 07-06-2017, 12:07 AM   #3
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Re: 72 fuse box upgrade needed?

Thanks, I will followup with the Mad Man
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Old 07-21-2017, 12:49 AM   #4
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Re: 72 fuse box upgrade needed?

No. I recently completed a wiring upgrade on a 56 pickup using a CS alternator. I added an IGN junction block as well as a common 12V on the firewall. I used a seperate run inside the cab as well as a larger feed to the ammeter. While a newer style fuse panel is desirable, for a few electrical add ons you dont HAVE to. I dont care to overload the stock ignition switch in the older trucks but regardless of what the big harness companies suggest, you can retain your stock setup and modify it if done properly and it will perform just as well.
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Old 07-22-2017, 07:05 PM   #5
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Re: 72 fuse box upgrade needed?

Thanks, what brand of junction box do you recommend? What is a common 12V on the firewall?

I also called and talked to Mad Electric. Very knowledgeable fellow. He wanted me to upgrade the whole wire circuit. I do not want to go that far. He will bend your ear.
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Old 07-22-2017, 08:13 PM   #6
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Re: 72 fuse box upgrade needed?

Quote:
Originally Posted by Robert Bergstrom View Post
Thanks, what brand of junction box do you recommend? What is a common 12V on the firewall?

I also called and talked to Mad Electric. Very knowledgeable fellow. He wanted me to upgrade the whole wire circuit. I do not want to go that far. He will bend your ear.
Mark has some good advice-I would listen to what he has to say. As for a common junction, look for a factory one on 73-up Chevy trucks. I'll see if I can find some pics of the 56 Chevy truck I recently wired.
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Old 07-22-2017, 11:58 PM   #7
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Re: 72 fuse box upgrade needed?

Just got back inside from doing some custom wiring....here are a few pics of the mods to the 56...

The bulkhead serves as the common BAT junction now where the leads from it are:

8ga to alt charge post
10ga to horn relay (which is also where the interior feed for the ammeter's from)
12ga lead to BAT +12V
12ga lead to ALT remote voltage sense
12ga lead to the dash mounted pushbutton start switch

coming soon will be a 12ga feed for the headlight relay upgrade and IGN relay too. The OE headlight/front lighting is trash so it's getting an upgrade. We're trying to keep most of the wiring basic but upgrading as we go-my father in law opted to NOT go with electric fans so this 78A SI charging system upgrade is plenty for this ole truck of his.
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Old 07-23-2017, 11:53 AM   #8
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Re: 72 fuse box upgrade needed?

Thanks for the photos.
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Old 07-23-2017, 06:38 PM   #9
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Re: 72 fuse box upgrade needed?

Here's a few pics of the new wire routing-tested it all out-very bright lights now! I ended up swapping to 56-series shells because the original 58-series stuff was just junk after 60+ years of use lol.

Now the front lighting is 200% improved, better quality Delphi grounding terminals, HD Delphi 59-series headlight terminals/shells-much improved.
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Old 07-23-2017, 06:42 PM   #10
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Re: 72 fuse box upgrade needed?

Heres the new relay bank underneath the oem horn relay. I used the hot lead as a junction for the various power to the relays. From left to right I've got HEI coil feed, low beam feed and high beam feed. Yeah those 70A relays are a bit overkill but I had em laying around lol
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Old 07-23-2017, 06:51 PM   #11
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Re: 72 fuse box upgrade needed?

Closeup showing the difference between the original wiring and the new-the purple feed is for dual filament parking lights up front but the truck has single element ones so unsure about that. Turn signals work just no parking light. Maybe in the 60+ years this truck has seen some "mods" over the years.
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