Just installed a new 1 wire alternator and need to install a fuse… what size fuse?? (1 Viewer)

[Landlover12]

Just installed a new 1 wire alternator and need to install a fuse… what size fuse??

Anyone have experience with this style fuse? I like the clean simple look but I want to make sure it’s the right style for the set up.

https://a.co/d/hBnMY5H

Currently running one battery on the FJ. It has a winch that I’m going to hook up. Used to have a two battery set up. Can I run the winch off one battery or do I need a second?

 

[Landlover12]

Specs on alternator in photo

 

[charliemeyer007]

I'd bet your starter pulls way more than 200 Amp, especially when its cold out. The alternator can do 91 Amps. I don't think this is a correct fuse for your application.

 

[Landlover12]

I'd bet your starter pulls way more than 200 Amp, especially when its cold out. The alternator can do 91 Amps. I don't think this is a correct fuse for your application.

Any idea on what size/amp fuse I should buy? Fj40 1978 2f

 

[charliemeyer007]

I'm not an automotive electrical engineer. Your old alternator was like 50 Amps and your wiring was fused for that. Now you have a almost double that but it is going only threw the wire from the alternator to the battery. I guess you could put like 100 amp fuse on that wire if you wanted. I think 2 gauge copper wire is rated for 100 A up to 20'

 

[pb4ugo]

Have you looked on mad electric's website. They have some good tutorials on 1 and 3 wire gm alt's and charging systems that use an ammeter.

 

[charliemeyer007]

Google says 4 gauge will do 100A at 5' in automotive application.

I would wire the alternator to the battery (giving up the dash ammeter) and used a volt meter to keep track of charge.

 

[Grayscale]

From the factory, the alternator charged the battery thru the ammeter not directly to the battery. The alternator powers the fuse block on the other side of the ammeter. By charging the battery, directly, that means that all the current draw will be routed thru the fusible link, thru the antique harness to the ammeter to the fuse block. Not all this current went thru the ammeter, before the reconfiguration, only the current to and from the battery. The original alternator was never serviced by a fuse, the battery was fused, but not the alternator. If nothing else, the ammeter will not read correct when the alternator is wired directly to the battery.

My buddy burnt his original harness via the charging wire at the ammeter, I'm not sure how his V8 alternator was set-up for charging, but, the ammeter connection is a common hazard in these rigs.

 

[Landlover12]

Have you looked on mad electric's website. They have some good tutorials on 1 and 3 wire gm alt's and charging systems that use an ammeter.

Thanks, I installed a volt meter so I can get a detailed idea on what is happening

 

[Landlover12]

I'm not an automotive electrical engineer. Your old alternator was like 50 Amps and your wiring was fused for that. Now you have a almost double that but it is going only threw the wire from the alternator to the battery. I guess you could put like 100 amp fuse on that wire if you wanted. I think 2 gauge copper wire is rated for 100 A up to 20'

Thanks, I’ll throw in a 100 am fuse

Going to order this one now https://a.co/d/8kHTnGV

 

[Landlover12]

Thanks, I’ll throw in a 100 am fuse

Going to order this one now https://a.co/d/8kHTnGV

View attachment 3802904

Oh also my goal is to run my winch off this same battery… does that change what size fuse I would need?

 

[Landlover12]

Photo of car

 

[offrd63]

I have run a 1 battery setup with a winch for 30 years. I have never had any issues, but I use my winch once or twice every couple of years.
If you plan on winching a couple of times everytime you go out then a 2 battery setup might be better for you

 

[Landlover12]

Do you have any fuses between your winch and your battery?

 

[charliemeyer007]

How many amps does the winch pull? Way more than 100 I'd bet. This 100 A fuse will only protect the wire from the alternator to the battery. Your winch needs big thick cables and likely has thermal cut outs to shut it off if it gets hot. Yea you could fuse it to the amp draw if you want to.

The amp draw of a Badlands winch depends on the weight it's pulling:

• No load: A typical 9,000-pound winch draws 60–70 amps when spooling in and out
• 4,000-pound pull: A typical 9,000-pound winch draws about 250 amps
• 9,000-pound pull: A typical 9,000-pound winch draws nearly 480 amps

 

[pb4ugo]

I've run 1 batt and a 8274 warn winch for decades. I use the winch a lot. 1st i used the gm alt with the stk wiring and ammeter. About 15yrs ago, I changed it to the gm alt around 90 amps or so with the 6ga charge wire going to the batt. I prefer the 3 wire setup. 1 wire looped to the alt's charge terminal because it needs 12 volts, and the other wire to an idiot light. The ammeter doenst work when the charge wire is run directly to the batt, so I bypassed it. The white wire connected to the batt and has a fusible link and supplies power to the fuse box, the white/Blue wire isn't used. I don't like the stk ammeter set up and charging the batt thru the stk wiring harness, 1st going to the fuse box and then to the batt thru a 10ga wire.

 

[Grayscale]

A serious weak link on any rig is the battery-positive terminal. Once corrosion creates a voltage drop between the alternator and the battery positive, you'll be compromising the alternator's connection to the harness, whereas before, it was only battery-resistance, the new configuration places corrosion-induced resistance on the alternator-source (voltage drop). If you are going to use the battery positive as a kind of cable terminal, you might have a vulnerability to the alternator. I don't know about 1-wire units, but Haynes manual states twice to never break the connection between the alternator's B-terminal, on a running motor, and the battery - that was with the externally-regulated units, maybe that is why the alternator is wired straight to fuse-block loads, instead of a path via the battery?

Also, the 10-gauge factory alternator charge wire, and respective fusible link at the battery, were never intended to run the whole truck, minus the starter and winch, just to charge the battery or to run accessories when the motor wasn't running. It might not matter that much.

 

[pb4ugo]

Also, the 10-gauge factory alternator charge wire, and respective fusible link at the battery, were never intended to run the whole truck, minus the starter and winch, just to charge the battery or to run accessories when the motor wasn't running. It might not matter that much.

In the stk configuration the batt charge or discharge goes in and out thru the ammeter. It's the only way the batt gets charged.

 

[DeskJock]

What circuit are you trying to protect?

Is you plan is to wire the new alternator directly to the battery? And let the old harness stay attached the the alternator - as normal?

What you don’t want to use is pull 91 or 100 thru a 50 year old design that maxes each fuses to around 20 amps.

Also, you need to consider bypassing your amp meter in your dash board or shunting it to not have a flash or a fire in your dashboard.

 

[TreadingLight]

I'm having some trouble following what circuits we are talking about here but maybe this is helpful:

* starter cable to battery + should not be fused
* winch to battery + should not be fused. However, it does make sense to leave the positive disconnected or on a battery disconnect switch until you are wheeling. This reduces the risk of your big fat winch cable dumping the battery into the frame in the event of a short (like in a front end collision)
* the stock alternator wiring is fine unless you put a big alternator in, in which case you want to bypass the (probably 30a) ammeter.
* if you intend to pull big amps off your alternator you may want a bigger cable from alt to battery with a fusible link at the battery. I've read that midi fuses have similar characteristics to fusible links so you could go that route.