Low voltage issue?
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From: Howard Lake, Minnesota
Low voltage issue?
I have been seeing low voltage on my Scan Gauge after start up. It has been in the 20 deg F lately and I have been driving my truck to work. I have not been plugging it in at that temp as it starts pretty good.
I noticed on Monday that when I started the truck it turned over slowly but thought it was because it had sat for 8 days. Next morning started it and it started good but the voltage on scan gauge was 10.9 volts. It sat at that voltage and then crept up a little until the high idle kicked in and then it went to 13.6 volts.
I have been watching it and pretty much same every morning. Was at work 12 hours yesterday and started it and drove it to put in fuel, (10 min run time) filled up tank and it turned over very slow but started. Voltage read 9.8 volts but went up quickly. Drove home (15 min) and shut off, checked volts with koeo and it was 12.4 volts. Load tested both batteries (two yrs old) and load tested good.
Sorry for the novel but is my alternator going or somthing else or normal?
I noticed on Monday that when I started the truck it turned over slowly but thought it was because it had sat for 8 days. Next morning started it and it started good but the voltage on scan gauge was 10.9 volts. It sat at that voltage and then crept up a little until the high idle kicked in and then it went to 13.6 volts.
I have been watching it and pretty much same every morning. Was at work 12 hours yesterday and started it and drove it to put in fuel, (10 min run time) filled up tank and it turned over very slow but started. Voltage read 9.8 volts but went up quickly. Drove home (15 min) and shut off, checked volts with koeo and it was 12.4 volts. Load tested both batteries (two yrs old) and load tested good.
Sorry for the novel but is my alternator going or somthing else or normal?
Logistics Pro
Joined: Dec 2004
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From: South Weber, Utah
I think the batteries are done, if it were the alternator the voltage would stay low. I wouldn't continue running with those batteries or you could end up buying an alternator and FICM in addition to the batteries. I just bought the diehard platinum batteries and im loving them so far.
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I just run my alternator scanning and posted the chart in another topic.
Those alternators do have slow start and the charging voltage climbs slowly for couple of minutes till it goes to 14V, so your observation might be normal.
Easy test for the batteries if you don't have load tester, is to turn the headlights on with engine off. Observe the voltage drop. The same with alternator, where additionally you can turn on the blower and whatever else you have in the truck.
Those alternators do have slow start and the charging voltage climbs slowly for couple of minutes till it goes to 14V, so your observation might be normal.
Easy test for the batteries if you don't have load tester, is to turn the headlights on with engine off. Observe the voltage drop. The same with alternator, where additionally you can turn on the blower and whatever else you have in the truck.
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From: Howard Lake, Minnesota
I do have a load teste and have tested them and they both show good. I will try a different load tester to confirm it.
Is the scan gauge accurate when it comes to checking voltage?
Is the scan gauge accurate when it comes to checking voltage?
Logistics Pro
Joined: Dec 2004
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From: South Weber, Utah
Load test the batteries separately ( completely disconnected from one another), check all of your ground connections and make sure your battery posts and cable ends are clean and making a good connection.
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From: South Weber, Utah
The scan gauge is just reporting what the PCM is seeing and is usually up to .4 volts lower than measured at the batteries, so I would trust what the scan gauge is telling you.
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Junior User
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If the truck starts at 20F after sitting for 8 days, that would give batteries respectable bill of health IMHO
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I think you are seeing the voltage right after start and you are seeing that the glo-plugs do to your battery. Wait 2 minutes after start before you even think of looking at the battery voltage. Or look at it BEFORE you turn the key on. On the Scan Gauge, touch the lower right button to turn on the screen. The alternator doesn't start charging until after the glo plugs turn off.
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Josh
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Joined: Dec 2004
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From: South Weber, Utah
I have been seeing low voltage on my Scan Gauge after start up. It has been in the 20 deg F lately and I have been driving my truck to work. I have not been plugging it in at that temp as it starts pretty good.
I noticed on Monday that when I started the truck it turned over slowly but thought it was because it had sat for 8 days. Next morning started it and it started good but the voltage on scan gauge was 10.9 volts. It sat at that voltage and then crept up a little until the high idle kicked in and then it went to 13.6 volts.
I have been watching it and pretty much same every morning. Was at work 12 hours yesterday and started it and drove it to put in fuel, (10 min run time) filled up tank and it turned over very slow but started. Voltage read 9.8 volts but went up quickly. Drove home (15 min) and shut off, checked volts with koeo and it was 12.4 volts. Load tested both batteries (two yrs old) and load tested good.
Sorry for the novel but is my alternator going or somthing else or normal?
I noticed on Monday that when I started the truck it turned over slowly but thought it was because it had sat for 8 days. Next morning started it and it started good but the voltage on scan gauge was 10.9 volts. It sat at that voltage and then crept up a little until the high idle kicked in and then it went to 13.6 volts.
I have been watching it and pretty much same every morning. Was at work 12 hours yesterday and started it and drove it to put in fuel, (10 min run time) filled up tank and it turned over very slow but started. Voltage read 9.8 volts but went up quickly. Drove home (15 min) and shut off, checked volts with koeo and it was 12.4 volts. Load tested both batteries (two yrs old) and load tested good.
Sorry for the novel but is my alternator going or somthing else or normal?
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The text highlighted in red takes the sitting for 8 days out of the equation, after sitting for only 12 hours the batteries were hating it, the system volts dropping under 10 and the slow cranking should be enough to cause alarm as that is NOT normal. The batteries are by far cheaper than the FICM and alternator that will be damaged by that low voltage. This winter we had 4 weeks of single digit and sub zero temps and my truck cranked just fine and the battery voltage never dropped that low. And during that cold snap I wasn't plugging in the block heater.
Sits 8 days drives it. Sits 12 hours starts the engine for 10 minutes and shuts off. Should have left the engine running while fueling up.
The batteries are getting killed.
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Now explain it to me, how alternator can be damaged by lower battery voltage?
I am still learning about FICM, but lot of owners use those truck in sub-freezing temperatures, so after long prewarming and long cranking the batteries are likely well below 11v for few minutes till the alternator do its thing.
If 11v is so danger for FICM the cold weather users would have it gone 10 times a season?
I am still learning about FICM, but lot of owners use those truck in sub-freezing temperatures, so after long prewarming and long cranking the batteries are likely well below 11v for few minutes till the alternator do its thing.
If 11v is so danger for FICM the cold weather users would have it gone 10 times a season?
Hotshot
Joined: Apr 2010
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From: Saratoga Springs,UT
there Cheap and Very Accurite
Now explain it to me, how alternator can be damaged by lower battery voltage?
I am still learning about FICM, but lot of owners use those truck in sub-freezing temperatures, so after long prewarming and long cranking the batteries are likely well below 11v for few minutes till the alternator do its thing.
If 11v is so danger for FICM the cold weather users would have it gone 10 times a season?
I am still learning about FICM, but lot of owners use those truck in sub-freezing temperatures, so after long prewarming and long cranking the batteries are likely well below 11v for few minutes till the alternator do its thing.
If 11v is so danger for FICM the cold weather users would have it gone 10 times a season?
Because the ALTERNATOR will continualy run at MAX Output trying to charge Dead Battery Cells
It will burn itself up in time