I start the car (84 kjet turbo):
the alt light is off, 10 volts on the voltmeter
I rev the engine:
the alt light comes on, 14 volts on the voltmeter
the tach reading is off by about 300 rpm
when I pull up the emergency brake the tach drops to zero and the alt light gets brighter. It stays this way even at idle after revving.
Sound like a ground problem? I have to dig out my voltmeter, but the alternator must be working if I am getting 14 volts on the dash voltmeter. Oh, yes the belts are intact and tight, Newer (used) alternator with brushes replaced about a year ago, engine wiring harness replaced (although it is homemade).
It just does not make any sense, the light and the gauge are saying the opposite.

Jessie I think it's in your instrument cluster. You could have a bad ground connection in it, or a crack in the circuit board. I think I would try to find another instrument cluster to be sure- the early ones with the mech speedo are pretty cheap these days.

Good luck!
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Rob Bareiss, New London CT ::: '87 244DL/M47- 221K, 88 744GLE- 202K, 91 244 181K, 88 244GL 145K

Sometimes my voltmeter reads low until I wiggle the key. The Tach's power comes from fuse 8. The brake light and others come from fuse 13. Hope this is of help.

seems your battery and starting is error free.
300 rpm is correct

the in dash voltmeter is an indicator and not very accurate,
but the wiring can have deteriote someware,
the same for the dynamo warning lamp

at least one of those 2 are faulty

to have the correct batt voltage, use an indepent portable voltmeter
to be reliable

can be a growing short cut somewhere fooling the system

connect the portable voltmeter to the measure point of the in dash voltmeter to read the voltage there, compare with the value the in d. V-meter is indicating
if different the id V-meter is faulty


the dynamo warn lamp is connected by a wire running from the dynamo towards the instrum cluster, check this also should I say


succes
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240 '88 B200K wite sedan 255K km Europe virgo+all turbo gauges, Phoenix Gold + Kenwood ampli, Focal door speakers + tweeters, Kenwood 6'x 9', 10 CD changer in enlarged globe cabinet, dubble rear coil springs , hitch, fog lights, 2 extra rectangular pencil