MEP-804A Under Voltage Frustration

[SSETRANSPORT]

I have an MEP-804A with a 50/60 15KW TRC Voltage Regulator that was running normally before the radiator leaked. I had the radiator fixed and reinstalled. When I went to start it, it’s giving me an under voltage fault light. I had found a previous post with the test sequence to check the TRC voltage regulator and found it to be no good according to the posted test procedure. Changed it out with a known working one and also replaced the KTK-3 fuse with a brand new one.

When I started it and tried to flip the AC CIRCUIT INTERUPTER switch to closed to turn on the 3 phase power, it doesn’t stay on. The frequency and voltage gauges jump when starting but that’s about it. Frequency gauge jumps and goes back to 48, voltage gauge goes to about 5.
When I hold the start switch in the start position, I can illuminate the AC Circuit Interupter and get the 3 phase power, but as soon as I let go and it goes back to the run position, the under voltage light comes on. Sorry for the long windedness but wanted to make sure I explain everything I came across first. Any help is very much appreciated. Thank you in advance!!

 

[kloppk]

When running and you have S1 in START do you get about 120 volts at the outlet?

 

[SSETRANSPORT]

Yes, I have 125 at the convenience receptacle when holding the start switch and 13 in run when I let go of it.

 

[kloppk]

Sounds like there is still and issue with the AC VR system. With S1 in START the set is Flashing the gen head to get it started making power.
When you release S1 back to Prime/Run the AC VR is supposed to take over regulation. It isn't.
The AC Voltage Regulation system is made up of:
- A1 AC Voltage Regulator
- T1 Transformer
- Front Panels Voltage Adjust Pot
- Resistor R16 on the back of the 50/60 Hz switch

I'd suggest performing the test steps in the TM for the TRC configured VR system and posting up your measurements for each of the test steps for us to review.

 

[SSETRANSPORT]

I unfortunately don't have any manuals for this unit. I used the test steps that you had posted in a previous thread for the TRC VR. Would that still be valid to use for this?

 

[kloppk]

You ought to download all the TM's that pertain to your 804A
Here is a link to download TM's and other great info on the 804!
---> 804 TMs
The -24 TM for the Generator has the detailed test procedures for the VR system and much more.

 

[Guyfang]

"Changed it out with a known working one"

The replacement was a TRC, right? You did not specifically say that.

 

[SSETRANSPORT]

Sorry for the delay. I had to get another multimeter as my original one decided it didn’t want to play nice. Lol.
Yes, the replacement VR is an exact TRC replacement as I have another MEP-804, that I think the blue governor box took a dive. But that’s another subject.

So, the test results that I have now are:

wire 141 disconnected from terminal 1 and positive multimeter lead connected to 141 and negative lead to terminal 3 is 10.9vdc.

multimeter connected to terminal 10 & 11, I get 163vac.

now, this is where I want to burn the whole damn thing.
Positive lead to wire to 137A and negative to terminal 4, voltage potentiometer to full counterclockwise position, the meter jumps anywhere from 1.6 to 5 and settles around 2.3. Turning it slowly to full clockwise position its at 18.2.

Hope that gives you the insight you need to help.

Thank you so much for the help this far!!