MEP-804a No Crank from S1 Master Switch

[SLTRAM98]

I have an 804a Genset, 164 hrs. on the clock. New to me (2006 make); here is the run down and trouble shooting to date.
1) Fresh batteries, when using the dead crank switch (on side of engine compartment), engine cranks totally fine, no issues.
2) When S1 (Master Switch) is turned to start, you can hear the shutoff solenoid open, but no crank.
3) Pulled Magnetic Pick Up (MPU) it did have some metal shavings but in great shape, cleaned it put it back in.
3) Read through the TM, traced things back to poles 18, 19 and 20 on A5 Governor Control board.
- Tested Poles per the test scenario's in TM, 18 to 19 'should be' normally closed when genset is off, but they are not. Note: I did notice a difference from the TM schematic which shows reversed NO and NC switches from the white markings on the GC A5 Board, appears to me that the A5 white markings are correct when genset is off, I guess the TM switch confi. would be accurate when the machine is running.
- Pulled A5 board out, its spotless, no burns, I do understand that only means so much but was looking for a blown up part, nothing.
- I JUMPED 18-19 poles to test my theory that their is a failed NC (normally closed) switch and genset STARTED right up, purred like new using S1 (Master Switch), ran no problem. I only let it run for a minute since I am not sure about the following items noted below.
- In the manual the wire diagram shows S14, but again reading on this forum, sounds like S14 is built into A5? (Please confirm this.)
- Am I correct in my understanding that the purpose of NC 18-19 switch relay at start up, which then should open after genset starts, is to protect the starter from getting hit again and grinding the starter? Eg; what happens if I cant solve S14 (built into A5) and install a wire jumper permanently?
- Does anyone have the A5 board schematic - specific to A5 - so I can see what else is driven by poles 18 and 19?
- Only other item I can see that 'may have' failed would be CR4, HOWEVER, it would stop power from getting to 18 so my jumper wire would not work regardless, so pretty sure that has NOT failed.
- I could install an external relay that is NC until startup, that would be pretty simple however, again I would like to know if anyone knows what else A5 is reading from the 18 and 19 poles. If no objection a permanent jumper would be nice.

Thank you for the help!

 

[Guyfang]

Before you get too far along. Have you troubleshot the S1?

 

[LuckeyD]

Good Day: I use the B model as it is better drawn but has the same things in there. OK, using S10 dead crank switch you know the K2 is working as it cranks. Guy hit the starting point with the S1. Battle short switch in the down position so the K15 will work or it acts like what you have, Emergency stop pulled out, and you should have Battery, (B+) on S1 terminals 2,4,6,8 to chassis ground(I use the ground point in the control box that looks like a stud on the one side but any chassis point will do). S1 to run and B+ at terminal 3. The blue stuff has power on the attached. Now go to start and if K15 energizes you should have B+ at A5 terminal 19, and if the S14 inside the A5 is good you should get B+ at terminal 18 out thru a now closed K15 contacts to K2 and it should crank below 900 RPM. K15 not working it acts like what you have. Over 900 RPM the A5 switch S14 changes position from what is fed to it from the MPU locking out the starter and the K2. That is the start circuit and should get you on a path to success. Let us know how it goes.... The A5 is expensive so if you do not go to start while running grinding the starter teeth, you can use a short wire between terminal 19 and 18 till a new A5 is available if the S14 is faulty for TS purposes. I did use a toggle switch once so I had power from 19 to 18 and after starting I flipped it to the other position so I had power to terminal 20 after starting so AC production starts till a new A5 was available as everything was working but the s14 inside the A5. Again let us know how it goes..

 

[SLTRAM98]

Guyfang - [Before you get too far along. Have you troubleshot the S1?] Yes, pole 7 is hot and all other poles are hot in the correct S1 positions, S1 tested good when I was going through the TM.

LuckeyD - Thank you for the info, I will go through this and get back with you this weekend! I know Battle Short is working properly and I verified Emergency shutdown is also good. Again, will go through your process and let you know asap.

 

[SLTRAM98]

Update:
Confirmed power at S1, 2, 4, 6 and 8, note - no wires connected to 2 or 6.
Confirmed power at S1 pole 3.
Confirmed when S1 in 'start' position, B+ at A5-19.
No, B+ from A5-18 when S1 in 'start' position.
K15 Relay DOES click over when S1 moved to 'start' position.
K21 Relay does 'lock' over when S1 moved to 'start' position; K21 does not release until S1 moved to 'Off' position.
Confirmed A5-20 has B+ when S1 in any position (except 'Off') and engine is off.

When A5-18 and A5-19 jumped, engine cranks and starts. Contactor trip lamp 'Under Voltage' illuminates and no AC voltage at generator lugs.

After allowing engine to run for 3-5 minutes, jumper wire removed from A5-18 and A5-19, the engine does start to 'hunt' it seems. AC voltage gauge holds steady, but the Frequency gauge starts jumping up and down; any adjustment with the knob causes the rpm to adjust some but begins to hunt again.

With engine running, A5-20 has B+ and A5-19 has B+, but A5-18 has around 4VDC.

Thoughts? The surging//'hunting' for frequency setting seems strange but could imply the Governor Control Board (A5) has more issues.

Thank you

 

[LuckeyD]

Good day: Your A5, S14 has failed. The moment you try to start the thing B+ is supposed to exit terminal 18 of the A5 thru the K15 contacts and the thing starts motoring over. As the engine goes over 900 RPM the MPU is supposed to allow the A5 to switch those contacts from 19 to 18 to the over 900 RPM of 19 to terminal 20 and while you are still holding the start switch in start it passes not the B+ thru the R14 and to the field to start producing an AC Voltage and the regulator kicks in. I recommend looking for an A5 for your gen set and a member sells these. Check new posts and I believe you will find him.

 

[SLTRAM98]

LuckeyD (and all) thank you for the help on this - does anyone know which components of the A5 board make up S14? Does anyone have any schematics of this board specifically? I have rebuilt boards before, just not A5 and this board looks great. Burn marks make repairs easy to find!

Note: I considered adding a separate relay assembly, but the signal needs to be fed somehow from the MPU on when to open/change positions.

 

[Guyfang]

The Military was not given any information on the A5. Its a Pluck and Chuck Item. Use the part number to find one on line. They are to be had.

 

[SLTRAM98]

Good morning all,
I wanted to close the loop on what I did on this genset.

After extensive board testing I found that the tiny yellow/amber colored capacitors which open and close the Black Relay (S14) were bad, S14 was actually not bad but was not being operated by the rests of the board. I worked offline with another member who was really helpful (thank you!) to tests different capacitors and options. Ultimately it looks like which ever part failed first failed in a way that it had a rolling failure to multiple components on the board. I stopped counting after 6-8+ bad components and started my search online to buy a replacement (I took the long road to get to the same place Guyfang said to go, pluck and chuck).

I found a 30kW GAC (Governors America Corp) board on ebay and after talking with GAC Tech Support, it is the SAME board as the 15kW board made by Woodward just made by GAC. The GAC board is impressively built, I have attached photos for others to judge... I thought it was so much nicer.

Either way, $400 and 3 weeks later, I installed in the generater, and she started right up, no issue. Per the GAC tech guru's I had to adjust the new 30kW board as the 15kW generator was running higher RPM and simply needed to adjust the potentiometers to get it back to spec.

Super nice upgrade from the original board in my opinion, I just wanted to let everyone know what I did to solve this one. I was NOT able to fix the original board, it was not worth the chase and the GAC board was an upgrade. Thank you again for each of your help on and off the forum!

PS - the board with the thick yellow conformal coating is the GAC board. The other board pictured is the original Woodward board. Image 9236 (showing the adjustment knobs required to adjust the board to run the 15kW genset).

 

[LuckeyD]

Super Cool! The 30KW A5 will have a slightly different transit response, that's it. It works. did it several times, after trying to repair those things. The 30 will work in a pinch on a 60. Not as good, but works to keep refer units going for food in the mess hall. The 15 on a 60 not so much. Tried it, and it just did not have enough to do it right. The adjustments are in the TM section if you have to refer to them. Two thumbs way up.

 

[Guyfang]

Good to go! And thanks for the heads up. Sadly, too many folks just walk away, and never share the hard earned lessons.