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  HomeArticles/VideosTechnical BulletinsFiat/LanciaTips on Reading Gauges >

Tips on Reading Gauges: Voltmeter

 





Tips on Reading Gauges: Voltmeter

The voltmeter will let you know if there is a problem with your charging system or battery. It is easier to use (and especially to install) than an ammeter. Learn your car's baseline voltages, so you can recognize when something may be going wrong. Here are a few possible voltmeter indications, assuming the car has been running enough to charge the battery. All accessories should be off:

VEHICLE STATEVOLTMETER READINGINDICATION
Engine not runningEngine off voltage is at least 12VSo far, so good. Note voltage reading.
Engine not runningEngine off voltage is less than 12VBattery run down. Charge before continuing tests. Cars with electronic ignition may not start, even if engine cranks.
During CrankingVoltage should be above 9.5VIf not, battery may not have enough capacity (too small or weakened by sulfanation or "old age.")
Increase engine to 1500rpmVoltage exceeds engine-off voltage by more than 2VProbable over-charging; look for bad regulator or regulator ground, or wiring problem.
Increase engine to 1500rpmVoltage exceeds engine-off voltage by less than 2VProceed to Load Test
Load Test: 3000rpm with all lights, heater & radio onVoltage exceeds engine-off voltage by less than 1/2 VoltCharging system may be faulty
Load Test: 3000rpm with all lights, heater & radio onVoltage exceeds engine-off voltage by more than 1/2 VoltCharging system ok
Any rpmVoltage regularly exceeds 14.5V. (May also blow lamp bulbs frequently, and/or tend to make battery run dry.)Probable over-charging; look for bad regulator or regulator ground, or wiring problem.

- Mark Lee


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All Technical Bulletins and Tech Tips contained on this website are based on our own experience, and are not necessarily "factory approved." While we make a reasonable effort to verify the information contained in them, we assume no liability for the use or misuse of the information offered.

*Overseas customers please note that our entire website is based on US-spec cars, as sold before the manufacturer left the US market: up to 1985 (Fiat/Lancia) and 1995 (Alfa Romeo). We do not carry parts for current models.