A Little Help Would Be Appreciated.....

[Ronmar]

Ok, so is your dash voltmeter no longer dropping to zero? Because there is nothing the alternator can do online, offline, tripped off on overvoltage that should be able to drop the dash voltmeter to zero. The worst you should see is a drop from 13.6/27.7(alt 14.1/28.2 minus diode drop) to battery voltage minus diode drop ~12.3/25.1. If your gauge is still dropping to zero it is not an alternator issue.

now an intermittent connection to the battery, that opens and unloads the alternator under load could be causing a volt spike that is causing the alt to trip out on overvoltage(red lights) and cause a volt drop in the cab…

 

[Rick_bagby]

Ok, so is your dash voltmeter no longer dropping to zero? Because there is nothing the alternator can do online, offline, tripped off on overvoltage that should be able to drop the dash voltmeter to zero. The worst you should see is a drop from 13.6/27.7(alt 14.1/28.2 minus diode drop) to battery voltage minus diode drop ~12.3/25.1. If your gauge is still dropping to zero it is not an alternator issue.

now an intermittent connection to the battery, that opens and unloads the alternator under load could be causing a volt spike that is causing the alt to trip out on overvoltage(red lights) and cause a volt drop in the cab…

Yes it does drop to 0. The voltage at the "E" terminal on the Voltage regulator is 26.4 - 27.8. According to C.E. Niehoff, the high voltage cut off set point 28.5 Volts. The Regulator is activating the cut off when the correct voltage is there. it is doing the same thing on the 12 Volt side. That voltage is 11.3 - 12.4. The HVCO for the 12 Volt side is 16.0 Volts. The regulator is shutting off both sides with the correct voltage being applied. on the N3207 voltage regulator Niehoff stated, "then something is wrong with the regulator" the LBCD will open the voltage/amperage to the batteries if it sees the spike, the regulator says there is a high voltage situation and shutting down the alternator when there is no high voltage there. It has to do with the "F" terminal I believe he said.

 

[Ronmar]

as I understand it, The voltage is not sensed on the excite terminal, it is sensed on the main output terminal bolts As that is the most direct path to the batteries which is what the regulated voltages are intended to serve. At any rate, that has nothing to do with the volt meter going to zero, as it SHOULD be hardwired to the batteries, so unless something is opening the circuit, that should not be possible.

an alternator generates output by using battery power to generate a magnetic field. The regulator controls the output to a set voltage by modulating the current used to build this field. It is generally considered poor form to disconnect a battery(the load) from an alternator, as it takes time for the regulator to react and even more time for the magnetic field to collapse. In the time between the load disconnect and the field collapse, the voltage will spike. This can be over a hundred volts…

your voltage regulator and alt may simply be responding to an over-voltage spike, because wether the alt is online or not, the voltmeter should never loose its connection to the batteries, but if the alt is loosing its connection to the batteries, it could easily create an over-voltage shutdown.

 

[GeneralDisorder]

Yeah that doesn't sound right to me either. The E terminal only needs a momentary voltage input to "start" the voltage regulator. Once it starts, the VR controls alternator excitation and monitors voltage, load, etc - the AC terminal is a PWM output from the VR that indicates load. The VR and alternator will continue to operate once spinning even if the E terminal is disconnected and the AC terminal doesn't matter at all as it is only an output that is either unused in the case of the A0 trucks or goes to the LBCD on the A1+ trucks.

 

[Ronmar]

They changed that output. On the A0 it was the F-, the end of the field that the reg would switch to ground to pull current thru from 24v applied to the other end of the field. Measuring there you would see 24v applied to the other end of the field winding, when running you can measure the regulator field duty cycle to gauge how hard the alt is being driven.

On the alt used on the A1 they switched that F- output to AC(RPM) so the LBCD would know what RPM it needed to start measuring if the output voltage was acceptable, to drive the dash light and the disconnect relay.

Somewhere in there on the way to the 260A alt they also switched the alt reg to providing a voltage to the field instead of switching the path to ground. I learned that troubleshooting with you @GeneralDisorder on your alt problem. I am not sure if they did that on the A1 100A but I suspect they did.

 

[Rick_bagby]

as I understand it, The voltage is not sensed on the excite terminal, it is sensed on the main output terminal bolts As that is the most direct path to the batteries which is what the regulated voltages are intended to serve. At any rate, that has nothing to do with the volt meter going to zero, as it SHOULD be hardwired to the batteries, so unless something is opening the circuit, that should not be possible.

an alternator generates output by using battery power to generate a magnetic field. The regulator controls the output to a set voltage by modulating the current used to build this field. It is generally considered poor form to disconnect a battery(the load) from an alternator, as it takes time for the regulator to react and even more time for the magnetic field to collapse. In the time between the load disconnect and the field collapse, the voltage will spike. This can be over a hundred volts…

your voltage regulator and alt may simply be responding to an over-voltage spike, because wether the alt is online or not, the voltmeter should never loose its connection to the batteries, but if the alt is loosing its connection to the batteries, it could easily create an over-voltage shutdown.

I think that there maybe more going on here than just a "simple fix". I think the first thing is get the alternator to supply power. To do that, I have to fix the HVCO situation indicated by the Red LED of the regulator. With the correct voltage now on the "E" and the regulator telling me its too high and shutting off, that is my first problem. I do believe that you are right in saying that should not make my volt gage drop to 0. That is going to be the next issue I fight. Are they related? I am not sure yet, but I am confident with this group of people and the awesome ideas being bounced around, we will find out. I will post as I get answers to keep everyone up to date as I can.

By the way, I believe it was Suprman that suggested checking the grounds. I did find the ground from Bat - to Alt GND was missing. I made a new wire for that and cleaned up the wire braided ground going from ALt GND to Frame. That did help in the performance a bit I believe also tying in your " the voltmeter should never loose its connection to the batteries, but if the alt is loosing its connection to the batteries, it could easily create an over-voltage shutdown. " Ronmar. Again. awesome ideas and a awesome group. Keep em coming.

 

[GeneralDisorder]

I'm assuming you are using a DMM for voltage measurement?

The DMM will not pickup transient voltage spikes and it will not show AC ripple - these alternators are very noisy and that's acceptable due to the brushless design. AC ripple up to +/- 2v is considered normal by Neihoff. You may not see a transient that the VR sees and so you might think the voltage is fine given the readings from a DMM but that may not tell the whole tale. To see what's actually going on you need an oscilloscope.

 

[Rick_bagby]

I'm assuming you are using a DMM for voltage measurement?

The DMM will not pickup transient voltage spikes and it will not show AC ripple - these alternators are very noisy and that's acceptable due to the brushless design. AC ripple up to +/- 2v is considered normal by Neihoff. You may not see a transient that the VR sees and so you might think the voltage is fine given the readings from a DMM but that may not tell the whole tale. To see what's actually going on you need an oscilloscope.

I am using both a DMM and an analog unit. That is the best I can do. The analog is showing me the fluctuations whereas the digital is only showing me that it is changing and hits P2P. I only wish I had an o scope. I cannot afford a decent one. LMAO.

 

[GeneralDisorder]

Scope's are really cheap now. Between my Picoscope, my Rigol, an old CRT scope, and a couple of hand held units I think I have about 5 or 6 scopes.

https://www.amazon.com/Oscilloscope-Bandwidth-HO52-Multimeter-Auto-Calibration/dp/B08VRDG94N