Overcharging Cummins
 

Hi all,
My 05 has been overcharging and slowly growing over the past 6 months. its now at the point on the gauge where its on the line past the "okay" range. Ive gone ahead and replaced the Battery temp sensor, checked all connections and cleaned grounds and terminals. I am getting 15.05 on both batteries evenly while running. I have two newer batteries in there, and have load tested both and theyre good. New alternator because a while back the field wire snapped at the pigtail so I initially thought the alternator was bad then replaced it and found that the pigtail broke off. That has of course been fixed and am back to the slowly rising voltages. I had a friend hold their hand on my bat temp sensor to trick the computer into thinking it is overcharging and getting hot and sure enough voltages dropped back to the center line on the gauge and never did have a voltmeter on when we did that. At this point im becoming concerned about where i could be. Any ideas?

Thanks in advance

Stupid question but are the battery terminals completely clean and tight? If you can wiggle the connector at all it is not tight enough. With all those new charging system parts sounds like it could be something with the Ecm

Yeah, I have gone and hit them with the wire brush and tightened and covered with protectant. What are your thoughts on a bad feed into the ecm from ignition switch? I replaced the switch once but its still sticky and I do have codes from the chassis I pulled with a friends scan tool if that could help?

also if its computer related do you think if i put a smarty tune in it would fix it within the reflash? I have a SR for the truck just havent had it on

You getting 15.05 volts with the truck running?
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Yes at idle, on both batteries

programming wont have an effect on that- it has to do with something within the electrical/charging system itself. You change Anything electrically/add anything before this issue popped up? Both batteries tested good but are they new/same age? I've had expierences where batts test okay but problems consisted until replaced

Yep, Both batteries are fairly new. One thing I was going to try tomorrow was a replacement of my ignition switch. I checked into the system when I had a short period of time with a genisys and pulled codes from the chassis, i got p1698, another for PRNDL switch circuit high, turn hazard switch input high. Unsure if these are related to the charging but nearly a year ago I replaced a faulty ignition switch with a much more faulty one. Its just a bit sticky and doesnt contact at the right points with the the key cylinder. Beyond that I doubt that will get it but its something im doing in desperation as Ive checked most everything else.

Update:
I put in the new ignition switch. It contacts where its supposed to now but the over charge is still there.

I have for the most part tracked the issue. I got it onto a scan tool. It was reading 14.80 as my target voltage and i had just slightly under that as the ecm voltage. Directly off the battery I was reading within a few thousandths of the ecm voltage. My gauge is definitely connected to the problem. When I shut the truck down, I noticed it wont drop all the way to the pin like every other gauge I have on there. But after maybe 30 seconds it does drop to the pin, open the door with the key out, an it goes back to its spot. Any ideas? Bad cluster? ECM? Thanks.

Also I had an 06 to compare with and its target voltage was higher than mine as well as its true reading and the gauge on that truck read okay.