Alternator output voltage when RPM drops

S

Shakespeares

Member
 TX, US
Hi everyone. Another problem here. I plot my battery voltage today. When the engine RPM is steady, whatever idle or running, the voltage reads 13.8V, which sounds normal. The problem is everytime I shift or something that let the RPM drops from 2-3k to idle, the voltage will also drop to around 12.4V for about half a second. At this time, I can hear the AC fan slows down. Is that voltage drops normal?

I have some codes with TPS and I have changed both of them. Now I think maybe the abnormal voltage from alternator may cause electrical problems.

Please let me know what you guys think. Thank you!
 
I expect to see at least 14.5 volts across the battery with the engine idling. Some places say a bit less than that.
 
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