Keep blowing “engine” Fuse, and I'm out of ideas. Please help. (76 FJ40 - US)

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the Larger Group batter will NOT cause your issue .......

but a CHINA made key switch could and i have seen it happen new out of the cheap bag they come in ...........


you get what you pay for in your land cruiser world ........


if you wish to eliminate this possible cause ?


i can have this in the mail today .......


100% Japan Spec. TOYOTA Genuine OEM parts .....







View attachment 3180705


View attachment 3180706
It’s been a couple of days, any chance I can get the order fulfilled? I’m dead in the water until I can try the new switch
 

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It’s been a couple of days, any chance I can get the order fulfilled? I’m dead in the water until I can try the new switch



remember this past Tuesday afternoon , right after you placed your order before lunch time , our discussion that your ignition key switch order was being EMS /

USPS Express Mail Overnighted to you :idea:




ems banner.jpg
 
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I'm having a hard time following here. We think that there is a short in the "engine" circuit because the engine fuse keeps blowing, right? I'd understand if the "engine" fuse was before the ignition switch, but, how could an open contact, or short to ground, at the switch blow the engine fuse or not melt the wire leading between the switch and the ammeter?

How does the fusible link look just after this vehicle's battery positive terminal?
 
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I'm having a hard time following here. We think that there is a short in the "engine" circuit because the engine fuse keeps blowing, right? I'd understand if the "engine" fuse was before the ignition switch, but, how could an open contact, or short to ground, at the switch blow the engine fuse or not melt the wire leading between the switch and the ammeter?

How does the fusible link look just after this vehicle's battery positive terminal?
Hmm, it SEEMS fine, but I'll need to look again. Maybe I missed something. If the fusible link was blown, nothing would be getting power though, correct? everything else seems to be working fine (lights , etc)
 
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remember this past Tuesday afternoon , right after you placed your order before lunch time , our discussion that your ignition key switch order was being EMS /

USPS Express Mail Overnighted to you :idea:




View attachment 3183538
I don't remember that conversation and can't find it, but glad to see the tracking number show up this morning. Thanks.
 
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Ok, this may be a dumb question but it dawned on me that maybe I was reading this backwards when I swapped the wires on my new regulator. This picture of the plug layout is supposed to be if you were looking at the end of the plug that's attached to the regulator, right?
It COULD mean the "regulator side" of the wires coming from the alternator, so I just want to check. If I'm wrong, then F & IG are swapped, and I assume that's bad.

IMG_3731.JPG
 
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Ok, I've learned a little more but it's led to another question. I used a multimeter to figure out which wires where which, traced them back to the alternator. The previous owner (who replaced the alt.) had wires going into E and N (even has N written on the wire connector, so it was on purpose), but NOT using the F terminal. Now my new regulator has E, F, and IG terminals.
Looking up the definitions here A key to help identify alternator terminals - https://shop.pkys.com/Alternator-Terminals-explained.html I see that F and N are very different things.

I'm a little afraid of just swapping wires and trying it, not wanting to cause more problems. Any thoughts on this? Should I run F -> F and ignore the N completely? That's the way it is in the shot of the system that I posted above. Why would he have used the N?
 
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Ok, I'll take a swing at it, now. I claim no expertise in these matters, but, I've probably owned a melt-down, hard to say what happened before the harness was removed.

I'd test this harness one fuse circuit at a time. Akin to the process described by @Engineer8000. Pull your battery, cover the terminals with the plastic caps that they were shipped with (I always carry a black one in my tool bag). You are looking for conductivity (ohms) between the small wire at the battery positive, or alternatively the big wire on the screw on the alternator, and any of these fuse spots, at various positions of the key. You should have conductivity between the "stop" and "engine" slot when the key is in any position. Which slots and what key positions get you conductivity?

Don't connect the battery until you get a fusible link on the battery positive. They are available at the corner auto store, and an undersized one purchased there could/would be excellent for troubleshooting purposes.

My guess is that the above photos were a result of amperage from the alternator and not the battery, as the alternator is not restricted to the main circuit via any kind of fuse fusible link. I'm pretty sure that your alternator needs further diagnosis, as the charging system can be a pain if got independently fried or fried in concert with the battery.
 
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Ok, I'll take a swing at it, now. I claim no expertise in these matters, but, I've probably owned a melt-down, hard to say what happened before the harness was removed.

I'd test this harness one fuse circuit at a time. Akin to the process described by @Engineer8000. Pull your battery, cover the terminals with the plastic caps that they were shipped with (I always carry a black one in my tool bag). You are looking for conductivity (ohms) between the small wire at the battery positive, or alternatively the big wire on the screw on the alternator, and any of these fuse spots, at various positions of the key. You should have conductivity between the "stop" and "engine" slot when the key is in any position. Which slots and what key positions get you conductivity?

Don't connect the battery until you get a fusible link on the battery positive. They are available at the corner auto store, and an undersized one purchased there could/would be excellent for troubleshooting purposes.

My guess is that the above photos were a result of amperage from the alternator and not the battery, as the alternator is not restricted to the main circuit via any kind of fuse fusible link. I'm pretty sure that your alternator needs further diagnosis, as the charging system can be a pain if got independently fried or fried in concert with the battery.
That’s a great info and I’ll be starting the testing tomorrow. To be clear, those pictures above were not mine
 
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UPDATE: I think it's fixed! I tracked down a short in the wire (F) leading from the voltage regulator to the alternator. I ran a new wire (capping off both ends of the old one) and at the same time adding a fusible link back into the system at the battery.
It cranked right up, no fuse blown. I turned it off and cranked it up a few times, then took it for a loop around the neighborhood and all seems good!

No idea WHY that wire would have shorted but I wonder if it had something to do with it going to N on the alternator (instead of F). I currently have it attached to F and everything seems ok EXCEPT....

I don't see the Ammeter going into the positive when running. Is this an issue?

I never watched it before, soI'm not sure of the normal behavior. Also, I have NO accessories and was not using lights or anything at the time.

Any reference experience from you all would be greatly appreciated. I don't want to drive it if I've got another issue to look into.
 
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My guess is that your alternator isn't charging. That might be a voltage regulator problem, but, it sounds like you now have it hooked it up properly. I wonder if your battery was ever over-charged, or if the rectifiers in the alternator were damaged? Do you have a Hayne's manual?
 

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