Reading the battery amp meter? On the dash

[russbabe]

My battery meter on the dash of my 1988 S4 has indications of 10, 12, 14 and 16. When I'm driving normally on the highway the needle is situated near the lowest reading 10 and doesn't seem to move upward into the mid or high range at all.
Can anybody advise on what this meter is intended to tell me and where should it sit in normal operating conditions. Thanks

[stepson]

Russ,
It should be somewhere near the 14. Check the function of your alternator with a multimeter at the jump post with the positive lead and a ground for the negative lead with the engine running.

[harborman]

The meter is not that accurate, more of a general indicator. Use a quality volt meter to get the true reading.

[JK McDonald]

Hey Russbabe - An erratic or low reading on the dash voltmeter is a common problem on our 928's as they age. It should read the same as the battery when the engine is off (key in the on position of course) and the alternator voltage when the engine is running. Test the alternator output voltage at the under hood "jumper post" and back at the battery with the headlights on and off just to determine if your alternator is charging properly. If the dash voltmeter is still reading low - the 1st place to check is for cleanliness of the battery connections and thoroughly inspect the short ground strap located along the lower right side of the engine block to the frame. The 2nd place to check is the black rectangular 14 pin connector found on the inner passenger fender near the ignition unit. You should disconnect the battery to remove power from this connector for safety - especially if using a small flat tip screwdriver to gently ease the two halves apart. Use caution because the plastic housing can be damaged or broken if you're not careful. The 3rd place to inspect is the electrical fuse/relay panel. Check that all your upper and lower fuse contact points are clean. I often inspect and spin all my fuses in place every few weeks just as a precaution during the humid Texas summers. Also just above the fuse/relay panel there are a couple of critical chassis ground points. It is best to remove the 10mm bolts so the copper ground locations and each terminal wire eyelet can be cleaned properly. Some 300 - 400 grit sandpaper (or pencil eraser) and alcohol works well.

If your instrument panel voltmeter is still acting up, the next step will be to pull the instrument assembly for an inspection and cleaning. Once the pod is removed inspect the rectangular push on connectors on the back side of the instrument pod and use an eraser to clean the ribbon wire traces. Here is a good write up on going through the back side of the instrument panel connections.

Instrument Printed Circuit Repair

There is also a good assortment of electrical connector, fuse panel, voltmeter, etc.... related fixes found in the "MOST Common 928 Issues AND Fixes" segment at the very top of the 928 page............

Good Luck and keep us posted on your progress, Michael