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Overcharging?

P40E

TCG Elite Member
Nov 4, 2012
9,151
4,472
All you have to do is put a volt meter on the battery posts while the engine is running and check to see what it's at at idle . And then hold the throttle a little and see if it goes up any . The volts should be around 14 .

If you dont have one you can go to auto zone and they will put a tester on it in the parking lot for free I believe , or one of those stores like it . If they try to sell you something just say you gotta check your money situation first . Then leave .

If you dont have a tester you can probably go to harbor freight and buy the cheapest one they got . It's like 2.99 lol .All you are doing is checking volts . Does not have to be expensive.
 

rocket5979

Gearhead
Nov 15, 2005
6,576
18
Round Lake, IL
test the positive pole on the alt that will tell you what its actually putting out

There will be no advantage to testing the voltage directly at the alternator versus at the battery terminals. Either way the voltage will read exactly the same; short of an immense (aka fire-worthy) resistance exhibited in the lead wire between the alt and battery.

Resting voltage should be around 12.5 volts. Running voltage will usually be between 13.5 - 14.5 volts.
 

Turbocharged400sbc

3800 & 4T80E > ALL
TCG Premium
Jun 16, 2007
32,542
15,849
hangover park IL
thats sorta false, measuring the two points will give you a voltage drop reading across the ground path, which is entirely usefull for diagnostic purposes, esp if the pcm uses the batt ground as the voltage ref point or the block sensor ground.

knowing what the batt, alt and pcm voltage/ground readings are is quite the advantage when starting out with this sort of a diagnostic issue.
leaving a gap in the routine/info is just shooting yourself in the foot
 

rocket5979

Gearhead
Nov 15, 2005
6,576
18
Round Lake, IL
thats sorta false, measuring the two points will give you a voltage drop reading across the ground path, which is entirely usefull for diagnostic purposes, esp if the pcm uses the batt ground as the voltage ref point or the block sensor ground.

knowing what the batt, alt and pcm voltage/ground readings are is quite the advantage when starting out with this sort of a diagnostic issue.
leaving a gap in the routine/info is just shooting yourself in the foot


I disagree when it comes to just doing a quick test. When doing a spot check to see if his voltage is indeed entirely too high compared to his gauge, measuring at the battery is totally fine. Sure, enough resistance in the wiring between the alt and batt will cause a voltage drop, but unless said power wire is really screwed then it will be a non-issue. A ballpark spot check is all that is needed for quick verification. If the OP receives a reading that is out of the norm, then take the time to dig a little deeper. No need to jump in the deep end first, when it may not even be needed.
 
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