Hey All,

I'm in the process of purchasing a 2005 Civic SI-G, and while the car in general is great, there have been some issues. The biggest has been a faulty alternator. I took the car to a Honda dealer for a comprehensive car inspection and they told me that the alternator had to be replaced as:
Alternator output @ no load = 14.37V (good)
Alternator output @ load (lights, AC, defroster on) = 12.54V (bad)

I took the car back to the used car dealer to get the alternator replaced, and they claimed to had replaced it. I then took it back to the same Honda dealer to get re-inspected, and they reported:
Alternator output @ no load = 14.34V (good)
Alternator output @ load (lights, AC, defroster on) = 12.50V (bad)

Just to be on the safe side, I took it also to a Honda performance shop, and they confirmed the low output... they mentioned that the alternator should produce an output of 13.0-13.2V, when under load. As a side note, all other electrical checks (battery, crank test, diode ripple) were normal.

What should the alternator voltage output be with and without load? Is this alternator bad? Should I hold off on the purchase until an alternator that produces an output of >13.2V be put in, or is that unrealistic? I've read other posts on this forum which say that the alternator voltage should be above 12V, but that seems too low according to Honda and the performance shops..

Thanks!

 

I did more research last night, and found a 7th gen Honda civic service manual, which contained an alternator test. The simple test procedure explains that the output of the alternator should be 13.9V and 15.1V when under load (radiator fan on, headlights with high beams on). Further, the alternator needs to produce an output of at least 60A @ 13.5V when under load (rad fan on, headlights with high beams on, blower motor, rear window defogger, brake lights, etc.).

The original and replacement alternator were both bad parts.. I hope the guy finally realizes and puts in a good part.. and I can finally get my Civic!!

 

Is this at idle? Most cars, including older Civics, will not hold up full voltage at idle with all loads on. It doesn't hurt anything. If you can get 13.8 volts by revving up the engine I would not worry about it.

Check that the pulleys are stock. If you have an underdrive pulley on the crank there's no way the alternator will do much at idle.