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HELP!! bad alternator or APPS??


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Today i went out and popped my hood to check the oil and noticed my drivers side negative battery cable was unhooked like it came loose. I thought i fixed my apps when i reset it but i must have just forgot to put the negative cable back on the battery. So is my rapid studdering a bad APPS? or is it a bad alternator? I do have the p0122 code and it cleared while the cable was unhooked.  I dont wanna replace one and have it be the other. But while the negative cable was unhooked i didnt have any issue with my shuddering. Im kinda stuck until i figure this out.cause i cant drive over 50mph without it shuddering like crazy. Any help would be greatly appreciated.

Thanks, kimber

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Can you explain shuddering a little better? Engine skipping, cutting out, vibrating or the like. How are you reading the codes? Little more info on the truck you are driving would help also. I myself have been dealing with some apps issues but the only thing I have happening is some surging of the rpm. Still very driveable.

Welcome.

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Its like the converter wont lock and its locking and unlocking.  I know the alternator can do this but with the 0122 code which is the apps,  Not showing up when the battery cable was unhooked it had me thinking it could be either of them. It only does it at 45mph and 55+mph it does it whether the od is on or off and with cruise control on or off.

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Be aware...

My alternator test GOOD. Now the crazy part the rear bearing was good but the rear housing was damaged allowing the alternator shaft to bounce. This in turn ate the brushes quick on one. Then it turn created a weak connection on the slip rings. Still pass the test bench though. :rolleyes:

Another way is to use a AC voltmeter that can measure small voltage like 0.01 to 0.1 AC Volts. Basically start the truck and with all your loads you can turn on. Now measure at the BATT post of the alternator red lead and your black lead just touch to either the alternator case or the passenger side NEG post. Best to test on the alternator case though.

0.01 to 0.03 is about normal.

0.05 is marginal. Might get away without problems or might be random.

0.1 AC volts and greater is a fail.

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Ok thank you,  so i can test it withouttaking it all out.  Im gonna do that first,  what are the chances this is my issue?  From all the posts of other people that have the same issues its the alternator.  If it is the alternator whats my best bet for a new one?  Should i get one woth higher amps?  With my airdog 150 im nlt sure of i should get a higher output or not. 

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Another thing to check out is all the connections to and from the alternator.  Up there in the rust belt especially.  Check the field wire and the feed wire from the alternator that routes from the alternator post to the fuse/junction box on the drivers fender.  Corrosion or a bad ground can make for intermittent high resistance and noise as well.  I am a big fan of dielectric grease on connectors!  

And by check, I mean pull them and wire brush the connecting surfaces off if they aren't shiny.  

Edited by CSM
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