Electrical problem
1997 Chevy Astro 6 cyl Two Wheel Drive Automatic 108000 miles
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My alternator was making noise and starting to burn the serpentine belt. I bought a used alternator, which did not seem to work. I have exchanged it twice, and the car is still not charging. I checked with a voltmeter, and there is about 13 volts coming out of the battery terminal on the back of the alternator. There is a battery fuse and an upfit battery fuse, both of which appear to not be blown. I tested these fuses with an ohm meter and found no resistance across the fuses. The positive battery cable coming from the fuse box to the battery also shows no resistance, and the negative cable from the battery to the frame shows no resistance. The replacement alternators I have gotten all have a four prong outlet, but the connector plug on the van is a two prong. I traded the original alternator in for the replacement one, and I did not notice if it had a two prong socket, but everyone assures me that the alternator for that model is a 4 prong. The two prong will fit on the middle two prongs, but the battery is not being charged, and the lights go dim, and the car stalls. Any ideas?

With everything turned off, you have bat voltage at the bat terminal on the alternator?

The two terminals at the alternator plug, are they hot, with the engine running? The lamp terminal is the brown wire and the field terminal is the gray wire. On the field terminal, it should be a duty cycle type pulse.

The info I looked at was for two wires at the wiring connector even though the alternator may have a four terminal socket.

There is only voltage coming from the alternator's bat terminal when engine is running. There is no voltage coming from either of the two wires at the plug. Any ideas? Thanks, George

What are the color of the wires at the connector that plugs into your alternator? Some of my info only shows one wire, besides the bat terminal.

I did find an astro with a two wire alternator plug, but that was a different year, not a 97.

One wire is black and the other one is gray with a black stripe.

My information doesn't show those wire colors.

Does the alternator connector have letters for the terminals? Is the L terminal hot with the connector plugged in and the engine running? Do you have a charge lite indicator on the dash, does it ever come on?

If that terminal isn't hot check the gage fuse. Not only check the fuse, check that the circuit, that fuse plugs into, goes hot when you turn the key on. Usually there is a bare spot on top of the fuse where you can check for voltage.