S60 Electrics: Testing for current draw

[dubstar116]

When testing fuses would a draw of 0.28A and 0.5A be enough to flatten a new battery in 3 weeks?

[Bernard333]

Depends on the capacity of your battery but think most car batteries would be completely flat within a week at that current , leaving a load on which reduces the battery voltage too far will leave it permanently damaged . The power you would be taking from the battery at 0.5amp for three weeks would be approx 3kWh , a large capacity ' leisure ' type battery as fitted to campers and caravans might survive , I destroyed what was a perfectly good battery in a V70 last winter , the drain from the alarm etc over a period of about 8 weeks parked up did the trick .

[grass hopper]

on this model leave the meter connected for 20 mins as it can take this long for all ecu's relays etc to close down.a standard reading is only 0.02 of a amp if alls ok,so naff all current draw.

had problems with non Volvo phone kits and non Volvo tow bars.

also door locks can cause feed problems than can be checked with vida on the lock status.

also faulty alarm sirens can cause high current draw,but this usually shows alarm service required !

[Georgey dee]

Stick an ammeter between the neg lead and the car from your battery then wait 20 minutes before reading. I was getting a constant 4 amp draw which turned out to be my alternator.

[agallo]

This sounds exactly like my issue! A previous poster had noted that perhaps it was a diode in my alternator. I haven't had the car looked at yet. In addition, I'm not too sure how to test if the issue is my alternator. My delay to having my car looked at by a garage is that I'm trying to avoid a steeler - as I also have a problem with my sun roof. It isn't sealing completely when closed.
BTW - the current draw I'm experiencing is exactly 3.84 Amps.

The funny thing is though - I left the car parked for 2 weeks. When I returned the car started! Weird! But, I drove the car for the day - about 1 hourd worth - and then parked the car over night. The following morning the battery was dead!
Could the alternator, if it's a diode issue, be dependent on how the alternator rests? In other words, the alternator spins, and stops at some point - perhaps at the point where the diode is shorted? I'm not sure if the alternator always rests at the same point.

Kind regards,
Angelo

[dubstar116]

Thanks grass hopper, funnily enough i'm getting the 0.5 A reading from the fuses that control the door locks. When i put the current tester in the fuse i can hear what sounds like the central locking clicking.

You mentioned that i should be bale to check them, how can i do that??

[grass hopper]

to check the door locks for correct status you would need to get them checked at Volvo as you need vida to read,might sound obvious but check all the courtousy lamps are off,including glovebox and footwell lights,also occasionally the boot catches can go faulty and leave the boot light on,one way to check is to lower the back seats down and have a look in when the boot is closed.

[rippedoffagain]

After the alternator (in most cars as far as I know) there is what is called a bridge rectifier. It is an arrangement of 4 diodes, often in a single unit, that fixes the polarity no matter what phase the alternator is in, and stops current flowing back from the battery into the alternator. If this fails, as can happen, then there's nothing to stop the battery discharging through the alternator.

I'm not talking car specific so some of this might not apply, but simply unplugging the alternator and then testing current draw would give you your answer.

An alternator (as opposed to a dynamo) always has its coild electrically connected to the terminals (via the brushes) so it wouldn't matter what position it stopped in, it would still draw current if the bridge rectifier had gone open circuit.

(Side note: I mention 'as opposed to a dynamo', a dynamo is effectively just a motor, in the the brushes briefly break contact with the coils as the armature rotates, and effectively swaps polarity to match the swapping polarity of the magnetic field that the coil is exposed to as the armature rotates - as far as I know we don't have dynamos on cars, so no breaking of electrical contact depending on position of the armature).

[Bernard333]

We always had dynamos on cars when I was a lad but your probably right you wont see one now , I can remember mates bragging about having bought cars with the new fangled alternator on them instead of being fitted with a dynamo , with a dynamo you got weak headlights and a modern car radio with 500W amplifier would have killed it stone dead , cars with dynamos were Austin 1100s / Minis / Cortinas etc .

[Georgey dee]

The 4 diode bridge or rectifier converts ac to dc but yes,,, when it breaks down it causes a discharge. In the S60s it seems to be a 4 amp draw.