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Old 08/01/20, 12:55 PM   #1
stroked 66
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4G alternator blowing 30 amp fuse every few days...

Hey Guys, I hoping someone has solved this problem already... Did the explorer conversion with a 4G alternator and new Centech harness. Trouble is that I am blowing the 30 fuse every couple of days. I'll try to attach a couple of pix and go from there... Main wire from the alt goes directly to the battery, clamp on ammeter shows 4-9 amps normal ops and a momentary spike to 20 amps when the high-beams are turned on...

https://classicbroncos.com/forums/at...d=1596307714re. imputs.
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Old 08/01/20, 01:11 PM   #2
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I'm surprised it lasts that long. Alternator can put out about 130A. But only delivers what is needed. 30A fuse will blow when the demand is great enough. They don't blow at exactly the rating, but about the rating with a time factor.

You just need a proper charge wire without the undersized fuse.

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
Why do people keep expecting "normal" from me?
Full throttle, it either solves the problem or ends the suspense.
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Old 08/01/20, 01:33 PM   #3
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I use one like this
https://www.americanautowire.com/sho...0aAoq4EALw_wcB

72 Sport uncut, 2.5 WH front coils 3.5 WH rear leaves pack
98 Explorer drivetrain
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Old 08/01/20, 02:38 PM   #4
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Or if you want one already made up with the cables and ready to go, we have this one: https://www.wildhorses4x4.com/produc...ronco_Starters
Same 175a rated Mega-Fuse, but with the cables to work with the 3G. In case you don't make your own.
Mega-Fuse replacements are readily available at most auto parts stores. And it would not hurt to have a spare in the tool box either, just in case.

Paul

'71 Wagon, 3.5" WH, F150 disc brakes and steering, 4.11 33x11.50 Thornbirds, Kayline soft top, Hanson bumpers. "Built, not bought"

'68 LUBR, 2.5 + 1 WH, 31x10.50, 4.56, Explorer and 4R70w by EFI Guy, WH disc brakes, Hanson front bumper, Warn winch. "Bought, not built"

www.wildhorses4x4.com
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Old 08/01/20, 03:22 PM   #5
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I'm surprised it worked at all???

#4-6 Cable with a 175A inline Fuse.

I like the Blue Sea Safety Hub 150 for all the high Amp Fuses.

175A Alternator
70A Chassis Harness
100A Stereo
35A EFI

All coming together in one spot. Not a mess of wires going in different directions.

1977 - Ford Wimbledon White, 351w, Sniper, AX-15, Duffs Street 4-Link, Hydro PDB, PS
1976 - Ford Magnetic Paint, Cleveland, Sniper, 4R70W, Atlas, Hydro PDB, PS, TDK Frame
1969 - Gobi Paint, Sniper 306, AT, PDB, PS, LUBR
1971 - Boxwood Green, Sniper 351C, WR Top Loader, PDB, PS
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Old 08/01/20, 03:32 PM   #6
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Probably worked because the battery was already fully charged, and only needed topping off after each start.
Once the demand went up for whatever reason, the undersized fuse couldn't handle it and just gave up on life entirely!

Paul

'71 Wagon, 3.5" WH, F150 disc brakes and steering, 4.11 33x11.50 Thornbirds, Kayline soft top, Hanson bumpers. "Built, not bought"

'68 LUBR, 2.5 + 1 WH, 31x10.50, 4.56, Explorer and 4R70w by EFI Guy, WH disc brakes, Hanson front bumper, Warn winch. "Bought, not built"

www.wildhorses4x4.com
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Old 08/01/20, 06:45 PM   #7
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Another reason it sort of worked, the sense wire was tied into the output pust. The voltage drop across the fuse let the alternator back off the charge. If the sense wire was tied to the battery as originally engineered the fuse would have blown at every engine start. (As it should have)

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
Why do people keep expecting "normal" from me?
Full throttle, it either solves the problem or ends the suspense.
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Old 08/01/20, 07:21 PM   #8
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Wow! Thanks for the great input guys. I wondered about the fuse rating (didn't know there would be that much draw at times.) I'll start the correct install tomorrow. Just to be clear, should I also relocate the yellow/ white wire that I have attached to the Alternator output terminal to the downstream side of the maga fuse pack that I will be installing. Once again, Thanks for the great support.
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Old 08/01/20, 09:06 PM   #9
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The yellow wire should skip the junction block as well. As close to the battery as possible. That is what the voltage regulator reads as battery voltage and adjusts the output to get the battery to the correct level. So if there is any voltage drop in the wiring (like your small charge wire and fuse) it won't read the battery voltage under load.

Most people doing the conversion just loop it like you have it. Super simple to do. Don't notice the slight voltage drop since the charge wire is often oversized to the point where there is very little voltage drop. It works, its quick and easy.

When I did the 3G there is the positive feed from the battery to the starter solenoid. A feed from the solenoid to a junction block that has all the various loads and alternator charge. This keep the battery terminal and the starter solenoid clean of the mass of wires. The only extra wire on the starter solenoid is the sense wire. That is only because it has a large gauge direct connection to the battery.

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
Why do people keep expecting "normal" from me?
Full throttle, it either solves the problem or ends the suspense.
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Old Yesterday, 03:24 AM   #10
stroked 66
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Ok, thanks for the info. Glad to see this will be an easy fix!
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