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Charging Voltage
Daddylonglegs - 17/8/12 at 01:59 PM

Now I have the new starter motor (see here) in I thought I'd double check the charging voltages as that was something I couldn't check properly before. Also, I had the problem of the ignition light staying and only going out if I blipped the throttle, then it would stay out.

The values I got are:

Ign off--12.79V
Ign on--12.71V
Engine running on tickover (950rpm)--12.49V

(Blipping throttle takes voltage up to 14+V and ignition light goes out - after that it stays out)

2000rpm---14.05V
2000rpm (lights on) --- 13.87V
3500rpm (lights on) --- 13.87V

So I think alternator is fine (apart from the initial kick start issue).

JB

mangogrooveworkshop - 17/8/12 at 02:26 PM

its fine dont worry about it as it makes equalisation voltage for a 13.8v battery

maccmike - 17/8/12 at 02:37 PM

spot on that

steve m - 17/8/12 at 03:19 PM

Anything over 12v is fine, mine is 13.4v but does go up to 14v if the battery is low

bi22le - 17/8/12 at 05:06 PM

Above 12 is good for fine at tickover.

13+ needed for charging.

Just make sure it dont sink to 9V when ign on and nothing started or ~15V+ at any time. Thens its regulator and battery bang gone time!

britishtrident - 17/8/12 at 06:13 PM

Although it is meeting the loads and charging at higher rpm however with an alternator the ignition light shouldn't really be on at idle.
The first thing is I would check the drive belt has enough tension and is not running in the bottom of the pulleys and is not worn/polished.

It may well be sign that the alternator could do with a new set of brushes with most makes of alternators this is generally a very quick easy and cheap job once the alternator is off the car.

There is an outside chance it could be leak back current through the alternator diodes but if that were the case the battery would flatten if the car is left overnight.

britishtrident - 17/8/12 at 07:15 PM

quote:
Originally posted by bi22le
Above 12 is good for fine at tickover.

13+ needed for charging.

Just make sure it dont sink to 9V when ign on and nothing started or ~15V+ at any time. Thens its regulator and battery bang gone time!



13.4v is needed for charging
Alternator unlike dynamos should charge at idle , this is the main reason alternators replaced alternators in the late 1960s.
A 12v lead acid battery in typical current UK temperature should show 12.8v when it has a decent charge in it in winter temperatures 12.5v is more typical.
A battery that shows 9v with only the ignition is either almost completely flattened or well knackered.
A battery in reasonable shape should show 10v+ when cranking the starter.

avagolen - 17/8/12 at 07:15 PM

The light on until blipped could be a sign that the
pulleys are not ratio'd high enough on initial start
and the alternator is not going fast enough.

Once the speed is raised to raise the voltage, the speed
is just fast enough to maintain output.

Daddylonglegs - 17/8/12 at 07:40 PM

Don't think it's a pulley issue as it's a standard pinto alternator. The light stays off once the engine has been blipped so it's not to do with the speed.

It sounds like I might be as well getting a bush kit and see if that helps.

As I said, it's not a problem at the minute, but I guess it could be a pre-curser to something later? I'll see if I can get a set of brushes just in case.

Thanks for the input guys