Charging voltages - Anyone able to check?

[Ibisa3]

Hi Guys.

Came out to car last night, failed to start. 09 plate 1.8tfsi with original battery.

Gave it a quick shove and it went no problems. 20 mins drive home, parked up, checked voltage @ cig lighter( it was raining....) 12.8v, but dropping fairly quickly.

ECP today, picked up a type100 bosch s4 for £70. Fitted with no issues, and drove home.

My question is this : Can any of you give me values for your own cars of charging voltage under full load, at tickover and say 2000rpm? I.e rear heated screen, fan on full, full beam and fogs on. Mine seems to dip down quite low, to around 13.2v. Tickover no load is around 14.1v

 

[LEE69]

pouring down here but should be about 14.4v
So you are not far off tbh

 

[Ibisa3]

Yeah,anything from 14-14.4v is all good with no load. IIRC the regulator on my alternator states 14v output.

Anyhow, my issue is the drop to 13.2v on load. I'd have expected the voltage to have come back closer to 14v ?

 

[LEE69]

It's still giving the battery some, no auto electrician but i'd say that was ok under load

 

[desertstorm]

I would say you may have lost a diode in the bridge on the alternator, 13.2v won't hardly charge the battery at all.
Try checking AC ripple on the car if you have a meter.


Karl.

 

[Ibisa3]

It's 14.1 off load, I thought about a failed diode, but surely that would show at tick over too?

 

[desertstorm]

When you lose a diode in the bridge you lose one of the phases from the alternator, so effectively a 1/3 of the output. Not so noticeable when there is no load. The way to check is look for AC ripple from the alternator. As in the video set the multimeter to AC volts and see what it reads.

 

[Ibisa3]

Hmm, my 'house' meter really didnt like reading it for some reason, it was jumping around all over the shop, from 1mv to OL. I have a fluke meter i can use, i'll try and grab it tomorrow.

thanks for your advice in the meantime. Fingers crossed it doesn't need an alternator, they seem to be pretty ££££