Charging System Issues

[abfisher1798]

I took both my 1088A1 and 1078 to my local EmpireCAT for regular PM service. At the time of drop-off, voltmeter in both trucks showed in the green at 28v.
Both trucks came back in the yellow at 24v. I went through the fuses and relays and could not find anything obvious. Sometimes the 1088A1 will show 28v after running for a while, and other times not at all. 1078 has never left 24v.
Empire says they have no idea why, that they didn't mess with it.

What's the solution? Did they make a mistake and how? I don't believe in coincidences.

Thanks.

 

[Ronmar]

Do you have a voltmeter? With the engine running you need to see 24v on the forward small terminal stud on the voltage regulator(that is the truck telling the alt to generate power). If that is there, do you have 14.1/28.2 on the large output terminals on the alternator case?

Does the A1 alt have led indicators on it, if so what are they doing?

 

[abfisher1798]

Do you have a voltmeter? With the engine running you need to see 24v on the forward small terminal stud on the voltage regulator(that is the truck telling the alt to generate power). If that is there, do you have 14.1/28.2 on the large output terminals on the alternator case?

Does the A1 alt have led indicators on it, if so what are they doing?

The A1 shows 24v on the forward small terminal stud.
Large output terminals are 12.5/24.69

The LED indicators on the A1 alt are flashing in an alternate pattern (front off-rear on, front on-rear off, etc.) with amber lights.

Disregard the 1078, I figured that out

 

[Ronmar]

The A1 shows 24v on the forward small terminal stud.
Large output terminals are 12.5/24.69

The LED indicators on the A1 alt are flashing in an alternate pattern (front off-rear on, front on-rear off, etc.) with amber lights.

Disregard the 1078, I figured that out

What color are the LEDs flashing? yellow or green?

24V on the forward regulator terminal is good, those voltages on the output, not so much.… so if all your grounds are good, one of two things is happening.

1. The alternator or regulator has issues.
2. The batteries are horribly depleted or damaged and the alternator is overloaded to the point it cannot reach regulated output voltage(14.1/28.2).

Disconnect the 14 and 28V cables from the large alternator output terminals and insulate them, then start the truck and repeat the measurements(now unloaded), forward regulator excite terminal and the 14 and 28v output terminals to the alt ground terminal. if the voltages are now good, look to a bad battery or really low state of charge. If they are not good unloaded with excite input, then the alt or reg is the issue…

if you are running 4 batts, drop to two. Pick the best two, fully charge them and install one in an inner position(close to frame) and one in an outer position and insulate the unused terminals.

 

[Ronmar]

I suppose you could also hook up a milivolt meter to the small terminals on the shunt on the A0 and read the current being sent toward the battery. every .001V measured on the small terminals = 1Amp of current passing thru the shunt…