Rep Power: 0

TLDR: Should the voltage always be above 14V while driving no matter what? Or is it common for it to drop down to 12.4 for a while (40 seconds)?

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I bought a cigarette voltmeter for another car I have. Whenever I reset the battery in my civic for the first 200 miles or so it'll almost stall at lights. I've read this is from the car using the stock idle and since my throttle body and IAC are dirty, it takes time to relearn the correct position.

Anyway, using this device I bought. I notice that when driving the voltage will drop down to 12.4 and stay there for a long time. Nothing seems to cause it either, no particular driving style, turning radio on, or similar.

When I get back and put my car in neutral (manual). If I pull 3 window switches up, turn the headlights on, have the a/c on, etc. I can get the voltage to drop to 11.4 or so.

I had suspected my alternator might be going out, and I'm wondering if this confirms?

 
Rep Power: 225

The alternator does shut off but I thought on the 7th gens it only did this when accelerating. While cruising/idling I thought it was always on. Searching through the service manual again.

Edit: Can't find anything in the service manual. It does say to turn the high beams on, raise engine idle to 2,000 RPM, battery voltage should read 13.9-15.1 V.