Charging issue (1 Viewer)

[Pirate0187]

Been having a charging problem recently. Symptoms began with low charge at idle. I was getting between 11.9 and 12.5 volts off the alternator. Replaced alternator with a reman Toyota, cleaned all grounds and all connections to the alternator and battery. Also did fusible links as mine were a little crusty.

I now get a good charge at start around 14.3 volts. However after 10-15 minutes it drops down to 12-13 volts at idle and I never see 14 even on the highway. Ambient temp is around 85-90. I’m thinking I should probably get the new reman tested, could be bad out of the box. Battery has been tested and is good. Anyone have some thoughts on anything else I could look at in the meantime?

Thanks

 

[Irish Reiver]

Been having a charging problem recently. Symptoms began with low charge at idle. I was getting between 11.9 and 12.5 volts off the alternator. Replaced alternator with a reman Toyota, cleaned all grounds and all connections to the alternator and battery. Also did fusible links as mine were a little crusty.

I now get a good charge at start around 14.3 volts. However after 10-15 minutes it drops down to 12-13 volts at idle and I never see 14 even on the highway. Ambient temp is around 85-90. I’m thinking I should probably get the new reman tested, could be bad out of the box. Battery has been tested and is good. Anyone have some thoughts on anything else I could look at in the meantime?

Thanks

When it comes to charging voltages the tenths matter. You say after 10-15 minutes you get 12-13 volts. 12volts not good. 13 volts at idle is probably in the OK range. How are you measuring the voltage? Dash guage, Fluke multi meter or something else?

 

[Pirate0187]

Fluke multi meter. I’ll grab an exact measurement tomorrow.
Thanks

 

[jonheld]

Alternator voltage will vary based on the state of charge of the battery.
14.4 VDC is the max you should see across the battery terminals if the voltage regulator is not faulty.
Voltage will decrease as the state of charge increases.
If accessories are added and load increases, the voltage should increase, but never above 14.4.

 

[LandLocked93]

^^^ this
Charge rate is directly related to batt charge level (running current demand notwithstanding).
At start up after a week sitting, I may see 14v initially @idle and up to 6 or 8A charge.
After 10 mins, I usually see about 1 amp of charge going to the main/crank batt @~13v @idle or @ speed. It does vary some with engine speed, but it regulates itself back down to 13.2v or so.
Batt voltage settles down to ~12.5V w/truck off after 30+ mins of running.
Alternatively, when there was a low intensity/intermittent short of the batt cable to the case of the alternator the crank batt showed 11.9v after two week sit and took about 40 mins of charging @~14v and averaged over 20 amps for the first hour. Was pushing about 45A @14.3v immediately after start up.

If your battery is confirmed good, and you aren't aware of any other electric issues, it sounds like your alternator is functioning normally.
What is your concern?

 

[Pirate0187]

Been a few days till I could get back to this, and it’s a lot cooler out now. Measurements are as follows.

Ambient 76 degrees

At rest 12.74 volts after 48 hours

Startup 14.26

10 minutes 14.14

20 minutes 13.94

30 minutes 13.82-13.83

40 minutes 13.79-13.80

I guess I jumped the gun and was being paranoid OR there is an issue and it’s intermittent. I’ll call it solved for now.

Thanks

 

[LandLocked93]

There once was a pirate from Nunya who bought a landcruiser to have fun, yeah?
After some checking, the alt was wrecking an 80 as fine as begonia.

If interested in that sort of thing, I recommend a voltage and current monitoring system.
It's one thing to measure infrequently for t-shooting.
But base-lining, then monitoring, can prevent ALOT of t-shooting.
Sometimes it even prevents tragedy.

 

[jonheld]

Been a few days till I could get back to this, and it’s a lot cooler out now. Measurements are as follows.

Ambient 76 degrees

At rest 12.74 volts after 48 hours

Startup 14.26

10 minutes 14.14

20 minutes 13.94

30 minutes 13.82-13.83

40 minutes 13.79-13.80

I guess I jumped the gun and was being paranoid OR there is an issue and it’s intermittent. I’ll call it solved for now.

Thanks

You started with a fully charged battery, so this is exactly what I would expect.
However you didn't include information on loads during your test.