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Ansbacher |
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#1
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Senior Member ![]() ![]() ![]() Group: Members Posts: 689 Joined: 4-July 14 From: Tampa Bay, Florida Member No.: 17,589 ![]() |
Simple question, I think. With engine running and no extra electrical loads turned on, my voltmeter reads a bit over 13 Volts. Turn on headlights and voltage drops to a bit above 12 Volts. Is that a normal drop or is something going on with the voltage regulator or alternator?
Ansbacher |
r_towle |
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#2
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Custom Member ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 24,591 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States ![]() ![]() |
At idle, normal.
At high revs, not normal. |
dlee6204 |
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#3
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Howdy ![]() ![]() ![]() ![]() Group: Members Posts: 2,162 Joined: 30-April 06 From: Burnsville, NC Member No.: 5,956 ![]() |
I would say it's normal if Youre reading off the gauge in the center console. The gauge isn't the most accurate for troubleshooting. If you want to really test it, stick a meter on the battery and turn on the lights.
Btw my gauge does the same thing and it charges normal. |
Tom |
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#4
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Advanced Member ![]() ![]() ![]() ![]() Group: Members Posts: 2,139 Joined: 21-August 05 From: Port Orchard, WA 98367 Member No.: 4,626 Region Association: None ![]() |
Depends on where the reading was being taken from. On or near the battery, it should remain fairly constant as you turn things on. As you get further from the battery, the loads will have a larger effect on the reading.
Tom |
screenguy914 |
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#5
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Member ![]() ![]() Group: Members Posts: 249 Joined: 6-July 09 From: So. Cal Member No.: 10,540 Region Association: Southern California ![]() |
Unless cranking the engine, system voltage should be about the same throughout the vehicle, including at the battery posts (12+V).
After starting the engine, the alternator's job is to provide enough electricity to recharge the battery and prevent it from discharging during normal operation. At full system load (i.e. all lights and accessories ON), the battery could be receiving up to 14V of voltage from the charging system, but above idle speed. Sherwood |
Ansbacher |
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#6
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Senior Member ![]() ![]() ![]() Group: Members Posts: 689 Joined: 4-July 14 From: Tampa Bay, Florida Member No.: 17,589 ![]() |
Yes, I was reading volts from the center console gauge. Sounds like I need to check it at the battery with my meter tomorrow. Thanks all.
Ansbacher |
Mike Bellis |
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#7
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Resident Electrician ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 8,345 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None ![]() ![]() ![]() |
Almost ALL old car alternators make little or no output below 1500 rpm. The exception is some old Dodge units make power at 1100 rpm. Newer cars are different with all the electronic systems many can make power at idle.
Your reading is normal at idle. |
76-914 |
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#8
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Repeat Offender & Resident Subaru Antagonist ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,513 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California ![]() ![]() |
That is one inaccurate gage. Everyone has that result; unless you run a dedicated + wire to the gage.
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Spoke |
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#9
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Jerry ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 6,992 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None ![]() ![]() |
The voltage you measure is expected of the center console voltmeter. I checked the voltmeter in my car with my multimeter and it was less than 0.25V different than my multimeter.
The voltage drop you're seeing with the lights on is a simple IR (current x resistance) voltage drop of 40+ year old wiring and connectors. You might get rid of some of the voltage drop by cleaning all grounds and battery connections. |
Dave_Darling |
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#10
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914 Idiot ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California ![]() ![]() |
The center console voltmeter is mostly there for "entertainment purposes". After you get used to how it works in your particular car, you can also use it as a quick check for if your lights are working. If the voltage drops by less than you expect it to, you may have a burned-out bulb...
--DD |
euro911 |
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#11
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Retired & living the dream. God help me if I wake up! ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California ![]() ![]() |
My center console voltmeter reads a little above 12v too, but drops dramatically when I hit the brakes or activate the turn signals. One of these days I do need to clean up all the connectors - it's probably just a corroded ground wire.
Voltage readings taken with a VOM (aka: multi-meter) at the battery show the true voltage and it's charging my battery fine (IMG:style_emoticons/default/smile.gif) |
somd914 |
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#12
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Member ![]() ![]() ![]() Group: Members Posts: 1,171 Joined: 21-February 11 From: Southern Maryland Member No.: 12,741 Region Association: MidAtlantic Region ![]() |
My center console voltmeter reads a little above 12v too, but drops dramatically when I hit the brakes or activate the turn signals. One of these days I do need to clean up all the connectors - it's probably just a corroded ground wire. Voltage readings taken with a VOM (aka: multi-meter) at the battery show the true voltage and it's charging my battery fine (IMG:style_emoticons/default/smile.gif) Exactly the same behavior on mine... |
TheCabinetmaker |
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#13
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I drive my car everyday ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 8,304 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 ![]() |
I'm gonna call foul on the old wiring thing. They showed the same drop when new!
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euro911 |
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#14
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Retired & living the dream. God help me if I wake up! ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California ![]() ![]() |
32 had passed by the time I acquired the 'BB', so I have no idea how accurate the gauge was when the car was new (IMG:style_emoticons/default/poke.gif)
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