Hi,
I have a 1999 Astro 4.3 Litre. The amp meter reads 14 volts until I put on some accessories such as the ac or wipers. The volt reading drops down very low (11volts) with the load placed on the system. I removed a battery cable with the van running and the engine continues to run which is confusing me because usually when a car is not charging it will cut off with the cable removed.. I feel that the alternator is bad but wanted another opinion. I tried a different battery in the van and had the same problem. Thanks in advance for any help.
Take care,
John

voltage drop is no good- the engine will run with very low voltage- it is one of the least current draws on your vehicle- remove the alternator- have it checked- I have a rebuilder rebuild the bearings, diodes etc- usually for $60

most alternator rebuilding shops will test your alternator for free. So will some auto parts stores. I would have the alternator tested prior to removing it from the van and then go from there -> alternator or battery. Just because the alternator gives you 14 volts does not mean that it is pumping out the amps it should and that might be where your problem is.

I thought for sure it would be the alternator after I switched the battery and that didn't fix it. I just replaced the alternator and have the same problem. When I first start the van it is putting out a bit over 14 volts. When I put on the ac, rear ac, and radio, the gauge drops to about 11 volts. It is charging, but the volts are low. Any ideas? Thanks,
John

check your battery. sounds like you have a bad battery. the alternator can not keep up with the demand of the battery sucking up juice and the accessories.

Thanks for the response. I already replaced the battery with one from my other car and had the same problem. That was when I figured it had to be a bad alternator. Now that I tried both I'm not sure what's left? Thanks,
John

Check the battery cable connections, both ends of both cables, for corrosion. They need to be shiny clean and tight. Inspect the entire length of the cables for cuts in the insulation where moisture can enter and cause corrosion. Also check the connections and insulation on the red 10ga wire from the back of the alternator to the battery. The battery needs to have the correct capacity and reserve. The alternator maximum output should be checked. Just because it's new doesn't mean it's good, ever buy a new car and have something go wrong? Hope this helps ;)