Chassis Voltage/ Over & Under Voltage Issues

[0533]

Hello Jim and Peter,

Both good thoughts.

Peter your ideas reminded me that when I am experiencing the problem I am also hearing some type of beeping noise almost like a muffled backup (engine in reverse) beeping sound. I assumed it was from the Jake Brake each time it comes on, is there a audible noise from the jake brake when its applied???

I also plan on checking all lights, the tow equipment etc. It is interesting that the problem has magnified when towing. I was having some intermittent issues before, but each time I was not towing but driving without the toad behind.

Also I have completely inspected and carefully taken each battery terminal and cleaned and sprayed each secured tightly all battery terminals, all good here.

I really feel now more than ever that the jake Brake plays some role here. It is also Ironic that I had Prevost Car go into the computer and change the Jake Brake performance recently as well,????

[Jon Wehrenberg]

Peter, I agree, but where I am heading first is to find out on the low voltage side if the regulator is shutting down the alternator because it is sensing high voltage. If it is, then the issue becomes finding out what is creating the high voltage, and I think the inverters can be ruled out because Bruce said this does not happen on shore power.

What makes no sense is why shore power does not do that making me wonder if the Genset alternator is somehow part of the equation.

I suspect two separate unrelated issues happening simultaneously by coincidence. One creating the high voltage situation and the second the low voltage situation. Do you agree?

[0533]

I am now back from the bus, have done some trouble shooting, here are the results: I did however learn that the problem also exists when the Gen or the Shore Power is on it makes no difference.

All readings are with Engine running 1000 RPM.

I. Alternator Readings:

1. Alternator: Without Gen running: 28.9 to 29.1 V
2. Alternator : With Gen running 10.1 V
3. Alternator: With Shore Power on, 9.8 V
4. Alternator: Without Gen or Shore at Low Idle, but with full load, all lights, dash air, Blower motors, OTR, Jake Brake on 29.7

II. Isolator Readings:

1. Isolator Without Gen: 28.1 House side, 28.1 Chassis side.
2. isolator with Gen running: 28.8 House side, 25.3 Chassis side
3. Isolator with House main disconnect turned Off. 25.3 on Chassis side.

III. Regulator

1. Regulator without Gen on: 28.0 at FLD 27.6 At Ignition
2. Regulator With Gen on: 27.5 Fld. 25.3 at Ignition

I also checked the lights, tail lights, the tow package, all wires and bulbs seem fine at a glance.

[Jon Wehrenberg]

Ignoring the high voltage / Jake brake issue for a moment I think I understand the voltages go down when the inverters are supplied with AC power.

I do not know what alternator voltage means, but regardless of where that measurement was taken it says if I am reading it properly, when 120VAC is supplied to the inverters, either from the generator or shore power, with the engine running the chassis batteries stop receiving a charge. They are at their normal voltage when no charging current is being applied to them.

Did I get that right?

If so, the next numbers I looked at were the value of the voltage to the regulator while this was happening. I did not see high voltages that would cause the regulator to disconnect power to the alternator field because the voltage was beyond the regulator set point.

Now, for reasons I have not yet fully considered, I am thinking the isolator may be the issue. If the coach were mine, I would disconnect the alternator terminal and chassis battery terminals from the isolator, bolt them together, start up the engine and generator and see what happens to the chassis voltage.

Don't ask me why just yet that I am thinking along those lines, but by doing this there is no downside, and it takes the isolator out of the equation as a potential problem if the chassis voltage remains low with the generator running.

All I can say right now is this might have something to do with the inverters being powered. Before disconnecting the terminals and joining them it would be of value to shut down the inverter battery charger functions while the generator is running to see if that has an effect.

[garyde]

Was there any discussion about the age and type of chasis batteries. Also, have all of the cables been cleaned and checked for connections. Finally, where the ground wire from the batteries lands at the frame of the Bus, is this in good condition? It sounds to me like a ground issue.

[gmcbuffalo]

What is the battery charging voltage reading coming out of the inverter/charger?

Could one bad cell in a battery cause the inverter/charger to send a high voltage to the batteries coupled with a bad (stuck on) isolator, therefore sending a signal to the regulator to lower the voltage coming out to the alternator?

GregM

[Jon Wehrenberg]

Greg,

That is where I was going when I inquired about the voltages to the regulator, but that does not appear to be the case based on Bruce's readings.

If the chassis charging rate goes back to normal with the alternator connected directly to the chassis battery terminal, bypassing the isolator I'm thinking the isolator may be the problem (I just haven't figured out how.)

[0533]

Chassis batteries are all good, terminals have been cleaned and secure, Bus ground is clean and secure as well. The chassis batteries are good, but thanks a lot for the advice.

[0533]

I plan on doing the Isolator Test today as Jon suggested. Hope this is the problem? But if not I guess I need to consider doing the same test (at least disconnect one side) with the Jump Start Relay to remove it from the equation as well, possible bad solenoid, stuck on as well.

[Jon Wehrenberg]

Bruce,

You realize when you get this solved you will know more about the bus than you ever imagined. Why is it we get experience just after we need it?