Finding a short
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6th Gear
Joined: Aug 2023
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Finding a short
I have a 99 F550 7.3 that seems to have a short somewhere.
I have burned up 4 alternators since last year.
Are there some common issues of shorting out somewhere that would be the first steps.
I'm not an electrical wizard, and the 2 different mechanics I have taken truck to just keep replacing alternator, as it seems to fix the issue for a few weeks.
Any help would be appreciated.
thanks
DD
I have burned up 4 alternators since last year.
Are there some common issues of shorting out somewhere that would be the first steps.
I'm not an electrical wizard, and the 2 different mechanics I have taken truck to just keep replacing alternator, as it seems to fix the issue for a few weeks.
Any help would be appreciated.
thanks
DD
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6th Gear
Joined: Aug 2023
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New one goes as high as 14.5 at 2000rpm
but it seems to slowly lose output in 1 hour drive. dash display went down to zero, and then truck quit.
I load tested batteries for the heck of it, they are about 1 1/2 years old. both check out fine.
But it does drain battery power to zero when alternator stops functioning properly.
Laughing Gas
Joined: Feb 2014
Posts: 817
Likes: 297
From: KY
Im not sure off the top of my head how much juice a 7.3 needs to keep going. For example the alt in my 99 V10 died a few weeks ago, but I made it some 3 hours home on battery only. A good fully charged battery will sit at 12.6ish when parked. Running you will see 13.8 to 14.3 at idle or some more rpm. Id think what might seem like a good short would smoke some wires or at least put such a load on the alt it would be screaming for mercy. I hate to say it but there is so much junk out there as far as parts these days Id not discount that as well. If you had a good fully charged battery, had it idling with the hood open to let some heat out does the alt or battery cables get really hot? Is it possible you have a hung glow plug/intake heater relay?
Laughing Gas
Joined: May 2024
Posts: 912
Likes: 294
From: E TN
Define short.
It sounds like the common poor quality auto parts we are now faced with. If possible I always opted for a good rebuilder to install quality parts in a factory alternator or starter. Unfortunately most rebuilders have gone away as they can't compete with cheapo new replacement alt and starters from the auto parts supermarkets so here we are. Battery condition and condition of all connections would have the biggest effect on an alternator.
It sounds like the common poor quality auto parts we are now faced with. If possible I always opted for a good rebuilder to install quality parts in a factory alternator or starter. Unfortunately most rebuilders have gone away as they can't compete with cheapo new replacement alt and starters from the auto parts supermarkets so here we are. Battery condition and condition of all connections would have the biggest effect on an alternator.
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6th Gear
Joined: Aug 2023
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Finding a short
Thanks for the info.
A lot of useful stuff, but once I see it on paper it seems to make more sense (sorry, ADHD).
dd
A lot of useful stuff, but once I see it on paper it seems to make more sense (sorry, ADHD).
dd
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Laughing Gas
Joined: Dec 2019
Posts: 896
Likes: 256
From: San Diego, CA
Most all the circuits should be fused. A short will pop the fuse and not create an electrical fire.
A short that would kill an alternator would need to be massive (guessing 70ish amps). That amount of current would burn up most wires on the vehicle, except for maybe the battery and starter leads. I'd probably check all large gauge wires for any burning, cracking or chafing.
Most likely cause is cheap replacement alternators... Do you know what type alternators are being used? Do you have any large non OEM equipment that would be pulling large loads?
A short that would kill an alternator would need to be massive (guessing 70ish amps). That amount of current would burn up most wires on the vehicle, except for maybe the battery and starter leads. I'd probably check all large gauge wires for any burning, cracking or chafing.
Most likely cause is cheap replacement alternators... Do you know what type alternators are being used? Do you have any large non OEM equipment that would be pulling large loads?
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6th Gear
Joined: Aug 2023
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HI.
Lol, this is about as basic a truck as it comes, other than power windows.
The ford dealer in my area doesn't even have the actual motorcraft one and I was in a hurry, again.
I am not sure of the brand but it definately is an aftermarket alternator.
I will check all the main wires this weekend.
thank you
DD
Lol, this is about as basic a truck as it comes, other than power windows.
The ford dealer in my area doesn't even have the actual motorcraft one and I was in a hurry, again.
I am not sure of the brand but it definately is an aftermarket alternator.
I will check all the main wires this weekend.
thank you
DD
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