Electrical problem...

[66 Tiger]

I have 8ga wire with a 40 amp maxi fuse installed between my alternator & battery. The fuse blew this morning ( without me knowing ) , & I pretty much killed the battery driving it to work.

After work I replaced the fuse & thought everything was fine. About five miles down the road the car started missing real bad so I figured the fuse blew again.
( I was right )

My question is - if the battery is not fully charged could that be the culprit with the fuse's? I went through four fuses this afternoon before finally calling it quits. Everytime I reved the motor the fuse would pop. I'm guessing there's to much load with the dead battery. Anyone have any ideas. Thanks...

 

[TheUser]

I have 8ga wire with a 40 amp maxi fuse installed between my alternator & battery. The fuse blew this morning ( without me knowing ) , & I pretty much killed the battery driving it to work.

I assume you mean 140amp fuse?

With a 3g, I would think you'd want at least 4ga wire.

Although I don't know for sure, you idea w/ the battery might be correct. I'd pull a battery from a friends car and see if the same thing happens. Do you know what caused the battery to go low to begin with?

 

[HISSIN50]

The state of charge should not have much to do at all with the alt fuse (we do need to clarify the wiring stuff - 8 gauge is what the stock wiring tapers down to IIRC).

One can jump a dead battery and run off the alt alone and not blow the fuse. Remember these are slow-burn fuses. The alternator has tiny spikes, but the slow-burn nature of the fuse keeps them from blowing every time a spike pops up. But a 40 amp fuse sure could burn.

I would look for a loose connection on the power cables from the alt to the battery or solenoid. Esp if you kept the stock wiring hooked up (with a 40 amp fuse) and ran a new cable (ran both in parallel). The new cable might have a poor connection or too much resistance, and the power is taking the lesser path of resistance - the smaller wire.

Good luck.

 

[66 Tiger]

I assume you mean 140amp fuse?

With a 3g, I would think you'd want at least 4ga wire.

Although I don't know for sure, you idea w/ the battery might be correct. I'd pull a battery from a friends car and see if the same thing happens. Do you know what caused the battery to go low to begin with?

I left the original alternator wires ( x2 yel 10ga ) hooked up to the new alternator. I then installed a separate 8ga. I kind of figured that would keep me from having to run a single 4ga.

The 40 amp fuse has always been sufficient. Occasionally it has blown - but I figured it had to do with starting the car when ALL the accessories were on... So maybe I should " up " the amperage of the fuse?

 

[66 Tiger]

The state of charge should not have much to do at all with the alt fuse (we do need to clarify the wiring stuff - 8 gauge is what the stock wiring tapers down to IIRC).

One can jump a dead battery and run off the alt alone and not blow the fuse. Remember these are slow-burn fuses. The alternator has tiny spikes, but the slow-burn nature of the fuse keeps them from blowing every time a spike pops up. But a 40 amp fuse sure could burn.

I would look for a loose connection on the power cables from the alt to the battery or solenoid. Esp if you kept the stock wiring hooked up (with a 40 amp fuse) and ran a new cable (ran both in parallel). The new cable might have a poor connection or too much resistance, and the power is taking the lesser path of resistance - the smaller wire.

Good luck.

You mentioned a 40 amp fuse could burn... What amp fuse would you recommend?

Far as the connections go - I replaced the alternator today too ( lifetime warranty at Discount Auto ), so I'm sure all the connections are clean & tight. I thought I would cover all the bases so I even replaced the ignition cylinder.

You also mentioned the factory wiring going to the IIRC. What & where exactly is that? Also - does the factory wiring have a fuse in line as well?

Thanks...

 

[HISSIN50]

You mentioned a 40 amp fuse could burn... What amp fuse would you recommend?

Far as the connections go - I replaced the alternator today too ( lifetime warranty at Discount Auto ), so I'm sure all the connections are clean & tight. I thought I would cover all the bases so I even replaced the ignition cylinder.

You also mentioned the factory wiring going to the IIRC. What & where exactly is that? Also - does the factory wiring have a fuse in line as well?

Thanks...

The stock 10 AWG cables taper down to an 8 AWG cable IIRC (If I Recall Correctly). It does have a fusible link on it and is good for ~ 50-55 amps continuous feed, IMHO.

The issue IMHO is all the cables you have run. I would go get a 4 AWG battery cable and an inline fuse and holder (125 amp fuse should work) and ditch all those little wires you have now. I still think you have a bad connection (resistive at a minimum) and so the power is being diverted through the wire with the 40 amp fuse.

For around 20 bucks or less you can redo it and have it be right. I would remove the new cable you added - toss it. Then leave the two stock alternator wires on the solenoid - just disconnect and protect them at the alternator side. Remember - those are still 'hot' cables.

Good luck.