MEP 803A Low AC Voltage and Alternator not charging.

[Medic1]

So I replaced the faulty oil pressure gauge on the front panel, ( see previous post) the sending unit and installed a manual gauge after the last post. The day after installing the new gauge I have dead batteries, so I jumped the unit with another and it started right up and now have no charging from the alternator and low AC voltage (190 from 240 and 90 from 120). my only thought would be the gauge some how causing this as that's all that has changed. the gauge works though it does read about 10psi lower than the manual one. My biggest ask I guess is, is there something simple I am missing before diving into the TM to test the VR and alternator? The gauge installed is a Veethree part# 127209 24v 0-80psi shipped with a sender to match.

 

[WWRD99]

The one thing I know is the alternator has a fuse of its own fu1...back of the drop down panel to the left...should be a Grey twist cap. If that's blown the alternator won't charge. It's a glass tube style fuse.

Sent from my SM-S906U using Tapatalk

 

[Medic1]

The one thing I know is the alternator has a fuse of its own fu1...back of the drop down panel to the left...should be a Grey twist cap. If that's blown the alternator won't charge. It's a glass tube style fuse.

Sent from my SM-S906U using Tapatalk

thanks I will go check it.

 

[kloppk]

The batteries going dead AND the alternator not charging may indicate failed diode(s) in the alternator.

Have you tried adjusting the AC output voltage with the front panel adjuster? Does the output voltage change at all?

When the set is running what AC voltage do you get at the outlet and you put S1 back in the START position?

When the set is running what AC voltage do you get at the outlet with S1 in PRIME/RUN?

 

[Medic1]

The batteries going dead AND the alternator not charging may indicate failed diode(s) in the alternator.

Have you tried adjusting the AC output voltage with the front panel adjuster? Does the output voltage change at all?

When the set is running what AC voltage do you get at the outlet and you put S1 back in the START position?

When the set is running what AC voltage do you get at the outlet with S1 in PRIME/RUN?

Voltage at the alternator with unit running is 24v - Note, we have a solar 24v chargers on all units and until yesterday have had no issue with any units holding a charge.

AC Volt at the outlet with unit running in Prime/Run was 94.2v

With adjuster full left - 81.5v at full right - 96.3v

with S1 held to start 119v at outlet

 

[Medic1]

The one thing I know is the alternator has a fuse of its own fu1...back of the drop down panel to the left...should be a Grey twist cap. If that's blown the alternator won't charge. It's a glass tube style fuse.

Sent from my SM-S906U using Tapatalk

fuse FU1 is good.

 

[WWRD99]

Voltage at the alternator with unit running is 24v - Note, we have a solar 24v chargers on all units and until yesterday have had no issue with any units holding a charge.

AC Volt at the outlet with unit running in Prime/Run was 94.2v

With adjuster full left - 81.5v at full right - 96.3v

with S1 held to start 119v at outlet

I'd ask what the battery voltage is, if you've charged them up, with the engine off. 24 volts running sounds low or the alternator is trying to charge 2 dead batteries...I'd avoid that 100% unless necessary to make power. The alternator might be going full field with amps trying to charge them both. Doing that usually ends up with a burned out alternator. Odd the solar charger didn't keep them topped off. Unless it's very small output it should keep them charged even with a small drain from a bad diode pack in the alternator.

Sent from my SM-S906U using Tapatalk

 

[Medic1]

I'd ask what the battery voltage is, if you've charged them up, with the engine off. 24 volts running sounds low or the alternator is trying to charge 2 dead batteries...I'd avoid that 100% unless necessary to make power. The alternator might be going full field with amps trying to charge them both. Doing that usually ends up with a burned out alternator. Odd the solar charger didn't keep them topped off. Unless it's very small output it should keep them charged even with a small drain from a bad diode pack in the alternator.

Sent from my SM-S906U using Tapatalk

I charged the batteries this morning with another unit, when I disconnected after charging it was at 24.9v. I have only run unit for short periods of time for testing only. The voltage drops slowly and continuously while the unit is running. It has a 20w 24v panel on it.

 

[WWRD99]

I charged the batteries this morning with another unit, when I disconnected after charging it was at 24.9v. I have only run unit for short periods of time for testing only. The voltage drops slowly and continuously while the unit is running. It has a 20w 24v panel on it.

Ok. Whenever a charging problem comes around in anything I approach it the same way. Keeping it simple starting with battery cables and connectors, then a solid battery charge and test. Alternator connectors etc. I'm not sure that the alternator can make the genset not produce power though so it probably has another issue as well. Is it sunny where you're at today? Could see if the solar charger is working. Be curious if the controller for it is not working right giving you the drain.

Sent from my SM-S906U using Tapatalk

 

[kloppk]

With the set running and the batteries are charged the battery/alternator voltage ought to be about 28.2 volts.

With the set running is the charge meter in the RED or GREEN and about what charge or discharge amps is it reading?
Remove FU1 and see if the battery charge meter reads the same as in the step above or not.

You might want to disconnect the solar charger to see if it's draining your batteries.

From your AC voltages readings it sound like you have a AC Voltage Regulator issue. I'd suggest performing the test steps in the-24 TM and post up the results of each test step.

 

[Guyfang]

Voltage at the alternator with unit running is 24v - Note, we have a solar 24v chargers on all units and until yesterday have had no issue with any units holding a charge.

AC Volt at the outlet with unit running in Prime/Run was 94.2v

With adjuster full left - 81.5v at full right - 96.3v

with S1 held to start 119v at outlet


Concentrate on one problem at a time. When you start the set, 24 VDC is to low. Period. If you saw the charging meter go up, than slowly drop down to 24 volts, that would be different. What you are reading, is maybe battery voltage, no more. To prove that point, unhook the batteries. Jump off the gen set, let it run a bit, and pull the jumper cable off. If the alternator is good, the set will continue to run. If it dies, the alternator is bad. Even if the batteries were bad, the alternator will carry the gen set.

 

[Medic1]

With the set running and the batteries are charged the battery/alternator voltage ought to be about 28.2 volts.

With the set running is the charge meter in the RED or GREEN and about what charge or discharge amps is it reading?
Remove FU1 and see if the battery charge meter reads the same as in the step above or not.

You might want to disconnect the solar charger to see if it's draining your batteries.

From your AC voltages readings it sound like you have a AC Voltage Regulator issue. I'd suggest performing the test steps in the-24 TM and post up the results of each test step.

Thank you I will complete the above and report back!

 

[Medic1]

I would like to thank all of you for helping me and others in this group. This is the only forum page I am on that you get quick, helpful and civil answers from.

 

[spotrep]

I would like to thank all of you for helping me and others in this group. This is the only forum page I am on that you get quick, helpful and civil answers from.

These are first class gentlemen for sure!

 

[CallMeColt]

When I used solar chargers of any type on these units, I installed an "off" switch to them because they will drain power checking the batteries in some form. This is not all of your problem, but some.

Sounds like a bad alternator from here, or belt not tight & it's not turning it enough. The two times I saw that, it made enough noise to notice.

 

[Medic1]

Results from voltage regulator test
Step H - 7.2 V

Step J - 89.7 V

Step L - 121.7 V

Step N - ohm range is 0.05 - 4521

 

[kloppk]

Step H - 7.2 V
This verifies the Flashing Function is happening and you've got continuity to the static exciter and that it's working properly.

Step J - 89.7 V
This verifies the Quad Winding in the stator is good and providing the correct AC voltage to power the AC Voltage Regulator

Step L - 121.7 V
This verifies the rotor is working properly and that the stator is able to output power properly and the sense voltage is getting back to the VR.

Step N - ohm range is 0.05 - 4521
This verifies the AC Voltage adjust potentiometer is working properly.

So.. all the tests above passed and assuming the Fuse Mod fuse is good then the verdict is the A1 AC Voltage Regulator is bad.

 

[Medic1]

Step H - 7.2 V
This verifies the Flashing Function is happening and you've got continuity to the static exciter and that it's working properly.

Step J - 89.7 V
This verifies the Quad Winding in the stator is good and providing the correct AC voltage to power the AC Voltage Regulator

Step L - 121.7 V
This verifies the rotor is working properly and that the stator is able to output power properly.

Step N - ohm range is 0.05 - 4521
This verifies the AC Voltage adjust potentiometer is working properly.

So.. all the tests above passed and assuming the Fuse Mod fuse is good then the verdict is the A1 AC Voltage Regulator is bad.

Thanks for the explanation it helps me understand for next time. Fuse mod checked and is good. I have the fuse and cap mods from your store installed on all of our units that did not have them when we purchased them. I have looked at your replacement VR on eBay this is a direct replacement correct? Is there anything I should look for before replacing it? I am concerned because it worked one day and gone the next. Is there something that could fry the VR that I should be checking prior to replacement?

 

[Guyfang]

This VR is not known for reliability.

 

[kloppk]

...VR on eBay this is a direct replacement correct? Is there anything I should look for before replacing it? I am concerned because it worked one day and gone the next. Is there something that could fry the VR that I should be checking prior to replacement?

Yes, essentially a direct replacement. Hook the wires back up to the same terminal numbers on the replacement VR. Install the provided pre-wired potentiometer in the front panel. Hook up two labeled wires behind the gauge panel. Done.

As Guy posted above, the factory VRs fail frequently and without warning.