Alternator Problem (EG Civic)

Hey guys

Have a small problem with my car at the moment. If I don't start it every day the battery seems to go flat (basically every second day goes flat). So I'm trying to work out whether it's an alternator problem or battery problem.

These are the readings I took from the battery today:

Car running (no load) 14.31V
Car running with hi-beams 14.07V
Car running with hi-beams & heater 13.10V

(If I take the readings directly from the alternator I'll get a higher reading by approx 0.1 - 0.2V)

If the voltage of the battery is approx 13V under load (hi beams on and heater on) does that mean the alternator brushes are worn? I'm pretty sure it's an alternator problem because I've tried another working battery and the alternator seemed to drain that battery aswell. Oh and it's also a reconditioned alternator which came with the car when I bought it.

So can someone tell me if it's a faulty/weak alternator and which parts I need to replace. I've read the DIY articles on regulator and brush replacements so I'm prepared to replace those parts if need be.

The car is an EG civic with 305CC century battery if that makes any difference.

Thanks

Sounds okay to me.

How old is the battery anyway?

Hmm not too sure how old, it was taken from another car so can't say exactly but test ok in another car. Current battery voltage measures 12.7V (car off) and water level is correct.

Just did another test.

Test Number 2:

Car off 12.7V
Car idle 14.52V
Car idle + hi beam 14.26V
Car idle + hi beam & heater 13.45V
Increase idle to 1500RPM 13.97V

From my understanding, these readings show a low output alternator under load. The reading shouldn't be any lower than 13.8-13.9V.

Does this mean the alternator is on the way out, possibly bad diode? Would a replacement be a better option than getting it repaired..

what's the voltage drop?
how many amps is the alternator

The voltage drop between the alternator and the battery?? or when the engine is under load with accessories?

you have to test both man

when you test with load on your suppose to test with everything on including wipers

Ahh ok.. but based on the readings above you can see the massive voltage drop when just the heater is turned on. Drops nearly 1 full Volt, wouldnt that mean if more accessories are on it will just drop more meaning the alternator is faulty?

1 volt is accpetable, test the regulator

i have a variation of +/- 1 volt from any of the following things in my EG8 (D15b7)
with pivot razin earth + stab kit + 2guage engine + trans earth

- power windows
- a/c
- hi-beams
- foglights
- full WOT
- phone charger in 12v port

etc

load test the battery by removing the terminals and using load tester on it and turn the knob half cca of battery