Ficm Posted September 2, 2014 Share Posted September 2, 2014 Got a weird one here. Operator complained about I/C and radio shutting off momentarily whilst driving. I drove the truck into my bay and it happened shortly after start up, engine kept running and I could rev it. I scanned for codes and got B1317 Battery voltage high. Perform two pinpoint test which included checking ground connections and voltage drop in A-circuit OG/LB wire. I proceeded to replace alternator. Monitored VBatt pid on start up and noticed charging system momentarily going 15.5V - 18V, when this happened I/C and radio went off. Charging system also hangs out 14.4V seems on little high side. I have also replaced the battery. It seems to happen when engine cold on start up, I could not verify whilst driving. Any ideas on what I am possibly missing? Quote Link to comment Share on other sites More sharing options...
Aaron Posted September 3, 2014 Share Posted September 3, 2014 Unplug the alternator 3 wire plug start te truck and rev it up a few times and see what the fail safe charging output is. Quote Link to comment Share on other sites More sharing options...
Aaron Posted September 3, 2014 Share Posted September 3, 2014 Maybe PCM is seeing low output, or the voltage isn't getting to the battery and therefore not getting back to the sense wire. What's your b+ Pid? Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted September 3, 2014 Share Posted September 3, 2014 Maybe PCM is seeing low output, or the voltage isn't getting to the battery and therefore not getting back to the sense wire. What's your b+Pid? Not pcm controlled. Take and back probe into the a akt at the alternator plug and install a jumper wire to the positive terminal of the battery, start it up and see what happens. Did you monitor your voltage drops with it running or just key off? 1 Quote Link to comment Share on other sites More sharing options...
Ficm Posted September 3, 2014 Author Share Posted September 3, 2014 Thank you for your inputs. I performed VD on A-circuit KOEO between unplugged connector at alternator and battery positive as per PPT. Quote Link to comment Share on other sites More sharing options...
Aaron Posted September 3, 2014 Share Posted September 3, 2014 I can never remember which are and aren't anymore. Plus today sucked outside and work was right next to awful all day. Lol Quote Link to comment Share on other sites More sharing options...
Ficm Posted September 3, 2014 Author Share Posted September 3, 2014 Hate those days! I'll try back probing when I get the truck back one day. Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted September 4, 2014 Share Posted September 4, 2014 Thank you for your inputs. I performed VD on A-circuit KOEO between unplugged connector at alternator and battery positive as per PPT. Voltage drop NEEDS to be done on a loaded circuit. Otherwise you aren't really measuring anything. I'll have to look at the pinpoint test later. You can load test with a fog lamp bulb on heavier circuits or a 194 bulb on lighter circuits and measure voltage drop on the circuit under load that way. Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted September 4, 2014 Share Posted September 4, 2014 Wow that is one really special pinpoint test. Quote Link to comment Share on other sites More sharing options...
Aaron Posted September 4, 2014 Share Posted September 4, 2014 Fuck it. I use a power window motor. Even on circuits with 20ga wire. Quote Link to comment Share on other sites More sharing options...
Aaron Posted September 4, 2014 Share Posted September 4, 2014 (Kidding, by the way) Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted September 4, 2014 Share Posted September 4, 2014 I got an old abs pump motor I keep handy for the 20 gaugers. Quote Link to comment Share on other sites More sharing options...
jimmy57 Posted September 4, 2014 Share Posted September 4, 2014 14 to 20 ga is gas starter motor, 12 gauge and bigger is diesel starter motor. V drop tests are best when the wire insulation is molten. If the insulation bubbles and smokes go down one stater motor class. 1 Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted September 4, 2014 Share Posted September 4, 2014 Quote Link to comment Share on other sites More sharing options...
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