Rep Power: 0

2005 Civic, The battery light stays on. Found the alternator to be loose. Alternator is now new and tight. Charges fine with no load but dies to 11-12 volts with AC and Headlights on. Sometimes the temp gauge will not work but if you shut it off and start back the gauge will then read where it should be. Any tests to narrow down what may be at fault?

 
Rep Power: 511

Two issues may simply be coincidence. When I had a voltmeter in my car, the eld would maintain battery voltage between 11.9 and 14.2 volts, seemingly sporadically varying with electrical/engine load.

The gauge problem could be grounding or connectivity issues. I could be wrong, though. For clarification, that's the only gauge affected, yes? Speedo, fuel, tach (if you have one), odometer work without issue?

 
Rep Power: 0

I've watched them all and that's the only one that will act up and it's not every time. It will not work on the way into town, cut it off, start it back up and it'll jump right to where it should be.
The voltage fluctuates just like that down to 11.8 or so and back up depending on load you put on it. I just don't understand why the charge indicator stays on ALL the time.

 
Rep Power: 517

The ELD system Honda has used for 3 decades acts real funny if you've never seen it in action. It can turn the charging system voltage up and down as it wants to, mostly for helping gain fuel economy.


With the engine running and the battery warning light on:
Disconnect the 4 wire plug from the alternator. Does the battery light turn off?