 Voltmeter reading? Accuracy? |
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| SKL1 |
 Jan 5 2026, 09:52 PM
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#1
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Senior Member  Group: Members Posts: 1,745 Joined: 19-February 11 From: north Scottsdale Member No.: 12,732 Region Association: Upper MidWest 
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Trying to figure out how accurate the OEM voltmeter is in my '73 2.0. To make a long story shorter the engine in the car is a much modified 1.9 from my '71, with approx 120K miles on the alternator.
Voltmeter reads around 11V and drops to 10 if I turn on the headlights. Immediately goes back to 11 or just over that with the lights turned off. Replaced the voltage regulator this AM and did a test drive with no change. Gauge never gets close or above 12V. Makes me afraid to drive it at night with the lights on and go very far. Do I need to go through the hassle of rebuilding the alternator or trying the alternator from the original 2.0 engine that has about 70K miles on it? Better way to get a more accurate reading of actual voltage?? I hate electrical issues!!!! TIA. |
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| SKL1 |
Jan 9 2026, 05:47 PM
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#2
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Senior Member Group: Members Posts: 1,745 Joined: 19-February 11 From: north Scottsdale Member No.: 12,732 Region Association: Upper MidWest
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Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6.
Not sure what the h*ll that means but obviously the OEM meter is kind of useless... Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif) |
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| Spoke |
Jan 10 2026, 09:28 PM
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#3
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Jerry Group: Members Posts: 7,300 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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QUOTE(SKL1 @ Jan 9 2026, 06:47 PM)  Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6. Not sure what the h*ll that means but obviously the OEM meter is kind of useless... Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif) @SKL1 As others mentioned, it seems your alternator/VR is not functioning. A couple of tests: 1) Is the GEN light on before cranking the engine? If the GEN light is not on then either the GEN light is burned out, or fuse blown, or an issue with the VR or alternator. 2) Once running, at the alternator connector on the relay board, measure (Don't disconnect anything): - D+ to chassis; should be 14V - DF to chassis; should be 5-9V - D- to chassis; should be 0.0V  |
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| 930cabman |
Jan 11 2026, 07:33 AM
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#4
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Advanced Member Group: Members Posts: 4,443 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States
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QUOTE(Spoke @ Jan 10 2026, 10:28 PM) QUOTE(SKL1 @ Jan 9 2026, 06:47 PM) Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6. Not sure what the h*ll that means but obviously the OEM meter is kind of useless... Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif) @SKL1 As others mentioned, it seems your alternator/VR is not functioning. A couple of tests: 1) Is the GEN light on before cranking the engine? If the GEN light is not on then either the GEN light is burned out, or fuse blown, or an issue with the VR or alternator. 2) Once running, at the alternator connector on the relay board, measure (Don't disconnect anything): - D+ to chassis; should be 14V - DF to chassis; should be 5-9V - D- to chassis; should be 0.0V Great information Spoke, thanks how is your 930 build coming along? |
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Posts in this topic
SKL1 Voltmeter reading? Accuracy? Jan 5 2026, 09:52 PM
mjrrti
Trying to figure out how accurate the OEM voltmet... Jan 5 2026, 11:16 PM mjrrti The brand didn’t show in my pic but it is zeehoo... Jan 5 2026, 11:22 PM 930cabman I have found voltmeter readings somewhat erratic, ... Jan 6 2026, 05:58 AM emerygt350 It's really not the voltmeter, I checked mine ... Jan 6 2026, 06:36 AM GregAmy
Trying to figure out how accurate the OEM voltmet... Jan 6 2026, 08:15 AM SKL1 Thanks. The meter in the lighter sounds great but... Jan 6 2026, 11:47 AM
Spoke
how is your 930 build coming along?
Coming alon... Jan 11 2026, 10:22 AM Superhawk996 1) Means your battery isn’t charging.
2) Means ... Jan 9 2026, 05:50 PM emerygt350 It means either the alternator is shot or your vol... Jan 9 2026, 06:09 PM GregAmy Yup, charging system inop.
Is you GEN light on? Y... Jan 10 2026, 02:39 PM |
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