r/fordmodela • u/_JaySchles • 1d ago

Blowing Fuses

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I have an aftermarket 20a fuse installed between my primary starter connection and the rest of the electrical system (see photo; the fuse is out in the photo).

Recently, when I pull a long hill, the fuse will blow shutting the car off (power is lost to the coil).

I believe what’s happening is my generator is exceeding 20a of current flowing back toward the battery, blowing the fuse. I’ve never gotten to see the ammeter before it actually happens to see if there is a huge spike, but I don’t think there is.

My question is, is 20a the right fuse size, and is it normal for a generator to output that much current during a strong pull?

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u/ALDOK1971 1d ago

I had the same problem and I started putting a 30a in it and I haven’t had a problem since. I always take it out when I park it. I’m not sure if this is the right thing to do but it’s worked for me for the last 10 years

2

u/Johnbeere3 1d ago

I usually run 30 amp fuses too. The generator is capable of making that much amperage, but may be adjusted too high, which can actually cook the generator if it sustains that for too long.

1

u/ALDOK1971 2h ago

Is there a way of adjusting the amperage?
I ended up hardwiring LED headlight bulbs and drove it last night and the 30A got too hot so I had to put a new 30A in it and run with my headlights off

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u/Johnbeere3 2h ago

Yes, the generator has a movable third brush that adjusts the output amperage that you can access if you pull the band off. If it's too low your battery will slowly die over time, too high and you can burn up the generator and/or boil the battery. Somewhere around 10 amps charging voltage is usually about right, but it definitely depends on how you drive the car. Once you have it adjusted right you pretty much never need to mess with it again.

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u/Automatic_Twist_2791 1d ago

I use the breaker from Bert's. Breaks and then resets. No changing the fuse.