Undervoltage Mep-805a

[rubioelectric]

I have a MEP-805 that is giving me undervoltage fault. I start it and leave it on start and you can see the voltage go up and then go down when let go. It used to be up for a bit then when you would close the circuit it would drop. I did the voltage regulator testing procedures I have the libby voltage regulator 122-3055. This is what I did and what I got. I go all of them the same output as the procedures except for J - I got around 147 VAC. The only thing I do not know if while taking this reading is that 141A is still disconnected or not where I tested J while being disconnected. Does this mean I have a bad Voltage Regulator. Also I removed the voltage regulator and installed a new capacitor and still the same thing. I do not think its the excitation because If left on start there is voltage. Any suggestions ? Should I get a new Voltage regulator? Green mountain generators sells something replaceable but is it plug and play like just put same wires as the old ones?

TM Test Procedure for Libby VR..


4-1.1 Testing (AC Voltage Regulator, P/N 01-21501-1, for MEP-804A/MEP-804B).
a. Shut down generator set.
b. Open output box access door.
c. Note position of voltage reconnection terminal board and set FREQUENCY SELECT switch to 60
Hz position.
d. Start generator set and turn VOLTAGE adjust potentiometer to ensure adjustment ranges on
Table 4-1 are met, depending on position of voltage reconnection terminal board.
e. Shut down generator set.
f. If no voltage or low voltage was indicated or voltage adjustment range could not be achieved,
perform the following steps. Otherwise, AC voltage regulator (2, Figure 4-1) is serviceable.
g. Disconnect wire 141A from terminal 1 of AC voltage regulator.
h. Set multimeter for DC volts and connect positive lead to wire 141A. Connect negative lead of
multimeter to terminal 3 of AC voltage regulator. Start generator set and operate at rated
frequency. Move and hold MASTER SWITCH in START position. Multimeter should indicate
between 4 and 12 VDC.
i. Shut down generator set. Isolate wire 141A.
j. Set multimeter for AC volts and connect to terminals 10 and 11 of AC voltage regulator. Start
generator set and operate at rated frequency. Move and hold MASTER SWITCH in START
position. Multimeter should indicate 210 to 280 VAC.
k. Shut down generator set.
l. Disconnect wire 137A from terminal 5 of AC voltage regulator. Set multimeter for ohms and
connect positive lead to wire 137A and negative lead to terminal 4 of AC voltage regulator. Move
VOLTAGE adjust potentiometer to full counterclockwise (CCW) position. Multimeter should
indicate approximately 3,000 ohms with FREQUENCY SELECT switch in 60 Hz position, and
approximately 0 ohms with FREQUENCY SELECT switch in 50 Hz position. Move VOLTAGE
adjust potentiometer slowly clockwise (CW) while observing multimeter. Multimeter should
increase smoothly to approximately 10,000 ohms.
m. If steps h, j, and l are as indicated above, AC voltage regulator is defective and must be replaced.
n. Connect all wires previously disconnected. Close output box access door.

 

[LuckeyD]

The manual tests all the external items, and if the S12, R16, Volt adj, T1 transformer are all OK they determine the regulator is bad. In the info file attached we got from OEM the TRIAC tests. I added the fuse addition they came out with later on. It protects the excitation circuits. So it boils down to check all external items to the regulator, and if they are all OK, then you look at the regulator as suspect. I'm attaching a large file. I'm working it right now so it will change and get a little smaller, let me know how it is helpful. I'm in the middle of how it works paper to add.

 

[rubioelectric]

I shall perform these tests again and keep you updated. I find it odd that before it was working and now it just does this. I keep reading that the voltage regulator is at fault. Let me get back on this horse and try again.

 

[Guyfang]

Its not odd at all. And I would talk to @kloppk about a new VR, before going to GM.

 

[rubioelectric]

I did these test that kloppk told me and this is what I got from the transformer

Terminals 1 and 2 on transformer S1 in START - 240 volts when let go its 43 volts

3 and 6 with S1 in START - 218 volts then goes down when let go.

I am about to check the wiring towards the vr.

It seems to me the transformer is doing its job but there seems to be no voltage when let START. Would this be a faulty VR?

I am going to check the lines from the Transformer to the VR although I think it wont do much since it looks pretty clean everything secured from last time I checked. Just going to double check..

Glad to see people still out here trying to help! Cheers!

 

[rubioelectric]

I performed the test from the input on transformer and on terminal 1 and 2 on transformer withe switch left on start I got 240VAC
On terminals 3 and 7 going to the VR I have no VAC meaning on VR 10 and 11 no VAC either. I find this so odd when before I was getting some voltage and now nothing. Is the transformer faulty? I had gotten about 147VAC on 10 and 11

I also noticed that I hear a noise on K11 when I leave it on Start and then let go. It is the voltage sensing relay and I think its just doing its job it senses voltage when on start then disengages when it drops in voltage.

Also my transformer sticket it says terminals 7 - 180v 6 - 60v 5 - 0v 4 - 60v 3 - 180v is this correct? or do I have a different one.

Could I have a faulty transformer since I get no VAC on 3 and 7? Or would this still be the VR?

 

[rubioelectric]

UPDATE: I installed a new voltage regulator that @kloppk provided everything is working now. The problem was I think the transformer was not the original but decided to eliminate transformer and old VR. New one is working great!