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Yes you'll need a TRC A1 to work with that T1 Transformer and Voltage Adjust potentiometer. S12 is the Frequency Select Switch. It's on a panel behind the drop down gauge panel.

The MEP-804A and MEP-804B may have either the Libby A1 or a TRC A1. Depending on which is installed when the generator was built the correct R16, T1 and Voltage Adjust potentiometer are installed to match the A1. Since you have a Libby A1 then you need to check the following to be sure your...

?? In Post #1 and Post #2 you said... Hello, is there anybody’s out there that can help me find a electronic governor control for a MEP 804B any help would be greatly appreciated Thanks Hello out there, I replaced A5 with the instructions provided unfortunately I still don’t get any power I...

Are you aware that the 804 used two different voltage regulators (VR)? Depending on which brand VR is used that the T1 Transformer, the R16 Resistor on the back of S12 and the front panel AV Voltage Adjust Potentiometer are different? Have you verified your set has the correct parts in it to...

Since you get power to the outlet with S1 in START it indicates the set if flashing and that the gen head should be OK. Now need to move on and see if there is an issue with the AC voltage regluation system. What brand of AC Voltage Regulator is in in it? Technology Research Corporation (TRC)...

Did you have power at the convenience outlet before you swapped the relays with S1 in START? With the relays swapped do you get power to the outlet with S1 in START and do you lose power there when you release S1 back to run?

That part of the job of the MPU. When the engine is up to speed and the MPU detects the RPM and causes the starter to be disabled. It also enables flashing at the same time.

Based on your measurements it indicates K15 is the problem. Odd because relays rarely fail. What should be happening is K15-7 gets 24 volts when the engine is up to speed. When you move S1 to START K15 closes and should pass the 24 volts on terminal 7 to terminal 4. However you are measuring 0...

OK Now with S1 in START measure the DC voltage at K15-7 K15-4 Also see if you see the K15 relay open and close as you move S1 from RUN to START and back to RUN while it's running.

OK now do these checks... With S1 in START measure the DC voltage at A5-18 A5-19 A5-20

All these tests must be done with the engine running. The MPU has to detect the engine is up to RPM before the field flash circuit can operate.

With S1 in START measure the DC voltage at A5-18 A5-19 A5-20

Now check K15 Terminal A then Terminal B with S1 held in start. A should be ~24 volts and B should be ~0 volts.

Was that with S1 held in START?

I'll be away from my computer for a few hours. Will be back on later.

OK, check CR4 terminal 1 for +24 V with S1 in the START position. Terminal 1 is the right terminal. CR4 in the bottom components on the parts panel in the back left. If you get 24 volts there then check the left terminal of CR4 for 24 volts with S1 in the START position.

OK now see if there is 24 volts DC at TB6-8 with S1 in the START position. Verify TB6-8 has 3 wires to it. Two on one terminal and one on the other.

Here is how the 24 volts gets from S1-7 to to CR4-1. S1-7 -------------wire # 190a ----------------TB6-8--------------wire # 190C-----------------CR4-1

If CR4 Terminal 1 doesn't have any voltage the problem is not CR4. Problem is the 24 volts DC isn't getting from S1-7 to CR4-1 or S1-7 doesn't have 24 volts DC on it when S1 in held in the start position. Did you verify that S1-7 has 24 volts DC on it with S1 held in the START position?

Looks like Guyfang is away from his computer so I'll give you some suggestions No DC voltage at VR terminals 1 & 3 with S1 held in the START position indicates there is a problem with the Flashing circuit in the set. I'd suggest the following to start and find out why. Try the following tests...