Alternator Problem (EG Civic)

[dorikin]

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

[flipfire]

Sounds okay to me.

How old is the battery anyway?

[dorikin]

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.

[dorikin]

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..

[na-118]

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

[dorikin]

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

[na-118]

you have to test both man

[na-118]

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

[dorikin]

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?

[na-118]

1 volt is accpetable, test the regulator

[TheSaint]

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

[na-118]

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

[dorikin]

I don't have a load tester unfortunately..

Ok did some more reading and supposedly you're not meant to load up the charging system on idle, only on fast idle (2000 RPM) so did another test.

Test 3:

Car on with high idle 2000rpm (no load) = 14.71V

Car on with high idle 2000rpm (with load hi-beams, heater, fan, stereo, demister, etc) = 13.90V

Is this acceptable for the charging system?

[na-118]

1500 rpm not 2000

[GenesisEG]

Sounds fine.

My guess is there's something running that's draining the battery between uses. I have the same problem, and I think it's my alarm.

Check the current draw on the battery with the car turned off.

It could be a light that's not turning off, or an alarm that's drawing too much current to run. Could also be an earth leak that's slowly draining the battery all the time...

Power problems are not always supply issues, it could be a constant drain, and it's probably easier to check that than it is to check the alternator beyond what you've already done.

[dorikin]

1500 rpm not 2000

There wasn't much difference at 1500 rpm.

Car on (no load) @ 1500rpm 14.58V
Car on (full load) @ 1500rpm 13.82V

Does the alternator sound like it's doing its job?


Sounds fine.

My guess is there's something running that's draining the battery between uses. I have the same problem, and I think it's my alarm.

Check the current draw on the battery with the car turned off.

It could be a light that's not turning off, or an alarm that's drawing too much current to run. Could also be an earth leak that's slowly draining the battery all the time...

Power problems are not always supply issues, it could be a constant drain, and it's probably easier to check that than it is to check the alternator beyond what you've already done.

That was my second guess, some sort of electrical draw while the car is off. I'll have to run some more tests. Do you know what the maximum electrical draw allowance is for a Civic? From what I've read the general rule of thumb is 50mA one hour after car has been turned off.

[na-118]

thats why i said do voltage drop to see if alarm or something else i drawing current from car, leave the multi metre on there