Alternator?
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 59
Not sure how you can get 5.9 volts... There are 3 scenarios:
Standing voltage... Which is usually 12.6 volts
Charging which would be 12.6+ volts
And battery drain which likely wouldn't get much below 10 volts with everything running, even with no output from the alternator
5.9 volts with the engine running means your DMM is fubar'd
Josh
Standing voltage... Which is usually 12.6 volts
Charging which would be 12.6+ volts
And battery drain which likely wouldn't get much below 10 volts with everything running, even with no output from the alternator
5.9 volts with the engine running means your DMM is fubar'd
Josh
Junior User
Joined: Dec 2012
Posts: 54
Likes: 0
Were you testing from battery negative to the positive post on the alternator to get that reading? Or were you checking the voltage on one of the little wires in the multi-wire plug?
If you were really only getting 5.9v across ground and the alternator output (Big wire), you probably have a bad alt AND bad wiring to the battery... Or a bad ground from the battery to the engine block...
Andrew B.
Logistics Pro
Joined: Dec 2004
Posts: 4,138
Likes: 7
From: South Weber, Utah
<p>Why wouldn't you go to the negative post on the battery? I would expect you would see system voltage measuring the charge wire from the alternator because it connects to the positive cable on the battery. Unless you had the charge wire disconnected from the alternator when you tested it.</p>
Lead Driver
Joined: Oct 2010
Posts: 5,420
Likes: 16
From: Ouray, CO
Maybe chaffed wires on steering wheel/column?
Sounds like key was switched to off "momentarily.
Wouldn't engine and lights keep running even
if you unplug battery(s)?
I have also had a bad cell which would cause my
tahoe to stall and dash lightstemp to go out. It would jump
start and idle as soon as i put it in gear and stepped on the gas engine would die.
Had it towed, new battery and alternator.
Shop believed bad battery killed alternator.
Sounds like key was switched to off "momentarily.
Wouldn't engine and lights keep running even
if you unplug battery(s)?
I have also had a bad cell which would cause my
tahoe to stall and dash lightstemp to go out. It would jump
start and idle as soon as i put it in gear and stepped on the gas engine would die.
Had it towed, new battery and alternator.
Shop believed bad battery killed alternator.
Thread Starter
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Mountain Pass
Joined: Jan 2008
Posts: 231
Likes: 1
From: Silver City, NM
Thought I'd give a follow up...
I bought a type 6G large case 135amp Alternator and had it installed by a co-worker with that also has a shop. He tested my old one as well and came up with basically the same reading that I got only he got 5.7 volts so yes you can get a reading that low, I knew I was not doing it wrong...
Any way, he also checked everything else we have discussed here and all was good. After installing the Alt everything is working great and it runs all electronics perfect. For my own piece of mind I put my volt meter on it when I got home and it reads 14.4 testing it exactly how I did before.
All is good again in Super Duty town...lol
I bought a type 6G large case 135amp Alternator and had it installed by a co-worker with that also has a shop. He tested my old one as well and came up with basically the same reading that I got only he got 5.7 volts so yes you can get a reading that low, I knew I was not doing it wrong...
Any way, he also checked everything else we have discussed here and all was good. After installing the Alt everything is working great and it runs all electronics perfect. For my own piece of mind I put my volt meter on it when I got home and it reads 14.4 testing it exactly how I did before.
All is good again in Super Duty town...lol
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Joe Kucinski
Senior User
Joined: Jan 2006
Posts: 141
Likes: 0
From: New Glarus, Wisconsin
So with the 135 Amp, you are charging 14+ Volts at idle?? With the wimpy 110 amp I get ~13.4 to 13.7. If so that makes my decision easy, gettin a 135 for ~ $160!!
Last edited by pile_53574; Feb 21, 2013 at 10:49 PM. Reason: Amps vs Volts
Thread Starter
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Mountain Pass
Joined: Jan 2008
Posts: 231
Likes: 1
From: Silver City, NM
I got mine here 6G Series High Output Alternator with Extra Heavy Duty Components for $189 made in the US of A. And as I mentioned its the large case style that were on the 7.3L strokes... Yep for about $40 or so more you can get more amps but I think the 135 is plenty for what I run, which is stock.
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 59
I got mine here 6G Series High Output Alternator with Extra Heavy Duty Components for $189 made in the US of A. And as I mentioned its the large case style that were on the 7.3L strokes... Yep for about $40 or so more you can get more amps but I think the 135 is plenty for what I run, which is stock.
99-07 7.3 and 6.0 are small case 6G. Some ambulance packages, snow plow and other dual alt setups used the large case 6G
Josh
