ECM voltage vs Alternator voltage
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Joined: Oct 2010
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From: Pemberton NJ
I do have a question along the same lines, not to thread-jack, I ran into the same issue recently, my voltmeter in the dash would read down at 10 or 12v right after startup and then after about 20 minutes it'd go back up to 14v or better. I went and had the batteries tested individually and together, together they were putting out 750cca, when each battery was rated for 750cca a piece. After that they tested the alternator, and there was barely 12.1 coming to the batteries with a full electrical load. I replaced the batteries and the alternator in an hour or so.
Now at idle after startup, there will be a click sound, the dash will light up brighter, and then click and it will go duller, and this will repeat 3 or 4 times before coming on bright and staying on bright. Is this normal?
Now at idle after startup, there will be a click sound, the dash will light up brighter, and then click and it will go duller, and this will repeat 3 or 4 times before coming on bright and staying on bright. Is this normal?
Registered User
Joined: Oct 2010
Posts: 475
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From: Pemberton NJ
Voltage and current for the charging system? It should be right around 14.5 volts and current will vary depending on load. Have you had the batteries load tested? Were both batteries replaced as a pair? If one battery is bad or going bad this could be your problem.
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Joined: Jan 2024
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01 Cummins alternator
I have an 01 Cummins. I started the truck and let it warm up for about 10 minutes. Then got in and turned on the headlights. About 5 seconds after that the voltage gauge went to zero and the "check gauges" light came on. I drove it for about 15 minutes and the truck ran fine.. Is it the ECM that is not working?
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