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MEP 802a producing 33.7 volts

K

Knuckles

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I have a mep 802a with 3 hours on it. Everything looks brand new. I fired it up and it shows no electricity being produced. Convenience outlets show 33.7 volts and lugs show 33.7 volts. Had anyone seen this issue before?
 
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K

kloppk

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When you start it hold S1 on the START position after it starts. See what voltage you get. Then realase S1 to Prime/Run and see what voltage you get.
Post up your findings.
 
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kloppk

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OK, now you need to see if the set is trying to flash the field.
Measure the DC voltage across the voltage regulator terminals 5 & 6. You should get ~ 7.6 volts DC when the set is flashing (S1 in the START position with set running)

If you get way less than that or zero then you may have an issue with the MPU or S14. The MPU has to detect engine RPM > 900. This causes S14 to switch allowing the set to flash. There can be other causes too.
To see if it's the MPU and/or S14 you can check the DC voltage at S14-1. It should be at ~ 24 to 28 volts DC if it's enabling field flashing (S1 in START with set running)
S14-1 is the left terminal in the upper row on the front of the S14 socket.
 
K

Knuckles

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Location
Marshall, VA
I went through everything again -
MPU reads between 2 and 3 VAC per the TM
I checked all the relays - they are good per the TM
K15 opens when S1 is in start

As stated previously voltage regulator terminals 5 and 6 momentarily show just over 19 VDC momentarily and then nothing

S14 - is this the crank disconnect switch? It did the same thing - it showed 19VDC - also replaced with one I know works and same result

K1 closes and I get 33.7 VAC at the lugs
 
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K

kloppk

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You indicated you get ~19 volts across the voltage regulator (A1) terminals 5 & 6 when flashing (S1 in START engine running).
If so the reading of 19 volts is way too high. It ought to be ~7.6 volts.
Since the DC voltage you are reading at A1 across 5 & 6 is so high it tells me there is likely a problem with the wiring from there to the Field Winding in the gen head or an issue with the field winding itself.

The field winding resistance should be 10.54 ohms to 14.26 ohms or about 12.4 ohms on average.

With the set OFF disconnect the wires to A1 5 & 6. Using your meter measure the resistance between the wires removed from terminals 5 & 6.
You should read about 12.4 ohms (the resistance of the field winding).
Reconnect the 2 leads to A1.

If you din't measure about 12.4 ohms in the test above then remove P5 from J5 and measure the resistance between pins 1 & 2 in P5.
You'll need to turn the locking collar on P5 before you can remove it.
It should be about 12.4 ohms. If you measure something way different then there is a problem in the wiring from P5 to the field winding or the field winding itself.

While you have P5 unplugged clean the 4 contacts in P5 and the 4 contacts in J5 and then plug P5 back in and turn the locking collar to secure it.
After cleaning P5/J5 and reconnecting them start the set and see if the voltage across A1 terminals 5 & 6 is still about 19 volts DC or closer to 7.6 volts DC when flashing. (S1 in START and engine running). Also see if you get ~ 120 volts AC at the convenience outlet when flashing.

Here is a schematic of the flashing circuit...
Filed Flash Schematic 802 803 3-10-21.JPG
 
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