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6.4L Power Stroke Diesel Engine fitted to 2008 - 2010 F250, F350 and F450 pickup trucks and F350 + Cab Chassis

Highly Voltage Problem

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Old Sep 29, 2018 | 08:17 PM
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Highly Voltage Problem

hello guys. So I picked up a new to me 2008 f250 last week. While driving almost every 10-15 seconds the dash, radio, gauges, would cut off and cut on constantly and the battery light was on. When I ran the codes I got a B1317 or high voltage. I measured the voltage through my scanner while driving and in fact it would jump up to 16-17 volts while driving.... not good. I checked the battery connections and the alternator and everything seemed tight and good, so today I replaced the alternator with an ultima 200 AMP reman alternator. First drive with truck absolutely no issues. Second drive the check engine light comes on and I have the same B1317 code, however nothing is cutting off so I am happy about that. Does anyone have any ideas of where I should look next?


 
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Old Oct 1, 2018 | 11:51 AM
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with the vehicle off

unplug the PCM control harness at the alternator...then check your voltages ....after stabilization with the harness off and a good battery.. you should get 13.75 volts. this is the voltage out put of the alternator in DUMB mode. after stabilization, if you are not getting this...theres a defect in either the alternator or the battery.

with the PCM control harness connected to the alternator and a good battery you should get 13.75 - 14.5 volts (alternator in SMART mode) depending on air temps.
 
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Old Oct 1, 2018 | 05:52 PM
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Here’s what I found with a multimeter. I’m starting to wonder if I gave it enough time for the system to “stabilize”... how long should that take after starting?

Alternator plug disconnected truck not running
13.37 battery
13.35 alternator

Alternator plug disconnected truck running
12.40 battery
12.32 alternator

Alternator plug connected truck not running
13.03 battery
13.05 alternator

Alternator plug connected truck running
13.98 battery
14.11 alternator
 
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Old Oct 1, 2018 | 06:15 PM
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I think these alternators kick in at 1200 ....and once you hit 1200...they will charge below 1200

depening on air temp, age of battery, engine drag, the needed charge time could vary.

i would disconnect the batteries and fully charge them on the bench

repeat the pcm plug disconnected test to see if you get 13.75 after the charging system recovers from startup.

 
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