KevinH

My battery went dead a couple of days ago and the meter was still in the last 1/3 of the gauge. When the new battery was installed the meter was in basicly the same spot. Is this gauge even necessary? If I had a 1.8T/S4 I would rather have a boost gauge there instaed.
Kev
98 2.8QMS

Leszek

It shows you the voltage at the battery terminals. If the engine is off, this will be the battery voltage, if the engine is on this will be the altenator voltage (which is higher than the battery voltage in order for it to charge the battery.) So, to check the voltage of the battery by itself, turn on the ignition without turning on the engine.

KevinH

nt

Audiboy

It's good to have gauges. At least while we are living in an analog world. But I would agree that in general the voltmeter gauge is pretty static unless the idle drops, the current load increases or the electrical system fails apart so in this case, a battery warning light will probably work ok to tell us that there is a problem, it's too late to address, so go drive to a shop. And then replace it with a vacuum/pressure gauge (turbo gauge) as that would be pretty dynamic just as oil temp and water temp - and of course - fuel.

In fact, most of us probably don't even see the battery gauge at all, even the oil gauge. So, usually when the battery gauge is in the red, or under 12V, a light will come up, and that's the only time it we notice. So when it starts to move away from normal - due to a belt getting loose, a battery running out of charge or the voltage regulator pops, probably don't see it until it's too late.

Safe operating range for the voltmeter is between 13 to 14V. Anything below 13V means that either the alternator is not turning fast enough to build current (such as in low idle or loose belt) or that the alternator cannot provide the current required by the system - in the case of running too many amplifiers or other high current devices. Anything under 12V means that the alternator is not charging at all - belt out? Brushes gone, voltage regulator gone. Above 14V (or 14.5 for A4?) means that the voltage regulator cannot regulate - due to no resistance against the alternator such as loose battery cables, no battery or the voltage regulator is shot. Anything above 14.5V is detrimental for the system because electronics is designed to operate from 0-16V at most, anything higher will smoke the system such as radios and ECU. A car run without a battery will make the alternator run at full voltage - about 18 to 20V and smoke will come out of the radio.

Your case sounds like a discharging battery - either a light on, or an accessory always on. Better have the system checked. If you have an ammeter, you can check yourself - or what I do, the spark test on the battery post. Make sure car is not running.

Ray Calvo

Blame above on a misspent youth.

Voltmeter is a good indicator of alternator/battery condition. While driving. should be reading approx. 14V; if less, likely have an alternator problem (and they CAN fail without actuating the warning lamp - school of hard knocks here).

Also, can check battery condition by turning off all powered functions (lights, radio, A/C blowere, etc). and with engine off utrn on ignitiojn. if it's reading greater than about 12.5 volts, battery is likely OK (if it's at 12V, is actually discharged or maybe you ahve a bad cell).

Patrik

...they would throw that thing out and replace it with a nice , moving pressure gauge that goes up to 1.0 bar ))

James R.

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