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Discussion Starter #21
3.4 volts at what engine rpm, and at what ambient temperature? The other day, you were getting 3.6 volts (conditions not specified).

I hope that fixes it, but the spec. at summer temperatures is 3.5 volts, and that would be at 2200 engine rpm or higher - a bit less at idle. Not sure where your 80% figure comes from. I'm skeptical, but of course we don't have all the specifics of how it was measured and under what conditions. There's also the question of how many miles it get's driven over a period of days, i.e., does it get driven enough to makeup for the starting drain plus normal ignition off drain.

With the new alternator, it would be interesting to know the charging voltage at the same rpm and at similar ambient temperature as he measure it at before.
as stated I measured thevolts across the battery and alsofrom the neg batt post with the meter red lead on the neg post of battery and the black lead on the detached neg cable(the meter was hooked in series with the battery and it also measured 13.4, when I took it in to be checked ,I DID NOT mention any test I did myself,just to see what the shop would measure and they got the exact same measurement i reved the motor up toabout 1700 rpms and it still measured about 13.49 volts even at higher rpms Idrove to a town which is 80 miles round trip last weekend,I drive it enough to keep the battery charged weekly 3-4 miles three times a week I will do the same 2 tests with new alternator to see the volt output,quiet sure itwill be around 14.3 which it should be
 

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14.3 would only be in cooler weather. The PCM adjusts the charging voltage according to ambient temperature: The colder the ambient, the higher the charging voltage; the higher the ambient, the lower the charging voltage - all within the range of 13.5 and 14.5, at 2200 rpm, and at some specified current (I forget what that is), but much above idle rpm, with some moderate current load, the biggest influence will be the ambient temperature. The biggest load that will affect it is the cabin fan on high speed. I'd say a moderate load would be headlights on low and cabin fan on low to medium speed. Turn the fan on high and you're likely to see a dip in voltage, especially at lower engine rpm.

Where are you located?

What's the purpose of measuring the voltage between battery negative post and negative cable with the negative cable disconnected from battery?
 

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Discussion Starter #23
14.3 would only be in cooler weather. The PCM adjusts the charging voltage according to ambient temperature: The colder the ambient, the higher the charging voltage; the higher the ambient, the lower the charging voltage - all within the range of 13.5 and 14.5, at 2200 rpm, and at some specified current (I forget what that is), but much above idle rpm, with some moderate current load, the biggest influence will be the ambient temperature. The biggest load that will affect it is the cabin fan on high speed. I'd say a moderate load would be headlights on low and cabin fan on low to medium speed. Turn the fan on high and you're likely to see a dip in voltage, especially at lower engine rpm.

Where are you located?

What's the purpose of measuring the voltage between battery negative post and negative cable with the negative cable disconnected from battery?
I`m in southern Illinois between St louis and Evansville Ind....I put my meter in series with my battery for volt reading also for a second reading it measured the same as across the battery posts 13.4
 

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I`m in southern Illinois between St louis and Evansville Ind....I put my meter in series with my battery for volt reading also for a second reading it measured the same as across the battery posts 13.4
That's what I was thinking. That's why I was scratching my head - thought maybe I missed something. 😁 👍
 
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