My Caravan wouldnt start a week ago so I got a jump start and drove to Advance Auto. The guy there hooked up his little machine and said the battery was bad so I let him install a new one. When I got home I looked at the printout he gave me and it says excessive ripple on the charging section. I went out after that and started the van, disconnected the battery cable. The van keeps running but the lights flicker a good bit. I checked the voltage with a meter and it shows its charging about 13.9 volts. Is it normal for the lights to flicker like that? It doesnt do that with the battery connected. Anyone have any ideas?

 

If it stay running with the cables disconected it's charging. the pcm controlls the charging it's on or off thats why your lights flicker. auto zone prob has the same type battery checker we use. I have had the exsisive ripple read out changed the alt and get the same reading your ok 13.9 is normal charge

 

Removing cables while vehicle is running is very BAD for your charging system

 

You're very lucky that you didn't blow the PCM and the body computer sky high. Disconnecting the battery cable is absolutely the worst thing you can do to test an alternator. Back in the old days before computers it may have worked, but not anymore. The flickering is definitely causing your flickering problem as the alternator is trying to "run away" with the voltage and the PCM is fighting to keep it low. I've seen alternators go up to 47 volts after disconnecting the battery cable. That's enough to toast everything electronic in your vehicle, including the radio.

Here's an in-depth article talking about the damage you could have caused. http://free-auto-repair-advice.blogs...lowing-it.html

There's always some level of AC diode ripple since an alternator produces AC voltage. The diodes convert it to DC. The question is how much is too much. Most of the computerized battery testers are pretty good at detecting the ripple. But I am a bit confused. If your alternator tested as excessive AC ripple, why didn't he replace the alternator? Although, the battery can act as a buffer to reduce the ripple effect. Maybe that's what he was thinking.