Mikesterling
model 96a06047-s serial 2031632
The unit starts fine and runs fine for about 5 minutes then shuts down with an overcrank error. You can reset it it and it will start again and run fine. the overcrank seems to happen more often on colder days. the unit always starts and runs. It never trips due to not starting. Many times it will not trip and run fine for hours. I cleaned and checked the gap on the magnetic pickup on the flywheel. Made no differance. The unit is older and is full industrial unit with the option C contoller. it only has 550 hours on it. any direction would be great.
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78buckshot
I'm not very familiar with the older controls, is it a R-200 rev. C or is the control just "C". Also did you happen to check the voltage on the mag pick-up while cranking and while running?
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Mikesterling
I believe it is just an option c controller. I did not check voltage on the mag pickup. My thought is that it is reading correctly because I do not get an RPM fault. Everything starts and runs fine but for some reason it thinks it isn’t running and I get the overcrank fault.

Thanks Mike
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cookelec
There is a console lamp on most C panel units. It is right at the top of the panel. Check to see when that light go out (assuming it is coming on). Is it when the engine stops or afterwards?? 
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Mikesterling
The console lamp does come on when the unit starts. I will check this weekend if the lamp stays on after the overcrank fault trips. I think it comes on and goes out based on engine running or not.

Thanks Mike
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cookelec
If it goes out when the engine stops, then you probably have a crank and latch board issue. If it goes out quickly after the engine stops then the problem is elsewhere. The crank and latch circuit should take a max of 128 seconds. If the gen is running for 5 minutes, it's likely not an overcrank condition. Also check to see if the starter is disengaging when the unit starts.
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Mikesterling
The starter is disengaging when the unit starts. I will time the run time to know for certain. I will check the light. Thanks for some direction.

Mike
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cookelec
If the starter is disengaging and the unit runs for more than 2-3 minutes, the crank and latch board is probably at fault.
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Mikesterling
You have given me a lot of things to look at. I will check it this weekend and let you know 1st of next week. Thanks a bunch.

Mike
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Mikesterling
Went to house on Thurs. Power was out and unit was tripped for overcrank. I reset and unit started. 40 sec later it tripped for overcrank. I reset and started it up in manual mode. Unit ran fine for 3 hours til power came on. I shut it down. Next day I ran it in normal test mode on automatic. Unit ran fine. Ran for an hour. Next day the unit was set to exercise. It started an ½ hour later than normal and triped around 40 seconds into the run for overcrank. I also noticed this unit have the optional relay for monitoring. The relay looks fine but it is 20 years old.

Your thoughts please.

Thanks Mike
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cookelec
I would say you either have an RPM sensor problem or the Crank and Latch board is flaky.
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Peddler
You may not be coming up to voltage.  I don't know that controller but if it uses AC output to let the controller know the engine is running and it fails to catch a field flash and doesent produce power it will fault for overcrank.  Put a volt meter on and see if the voltage come up to nomal when it faults.  
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Mikesterling
Thanks for the info. I am changing the latch board, alarm solenoid the ribbon cable and the relay that sends the power to the starter solenoid. Some additional bizarre information. For the most part I had no issues all winter when I had the block and oil heater plugged in. when I shut down the block heater for the summer the overcrank issue happened all the time. The block heater is 1000 watts and is on its own circuit. Not part of any generator wiring. I ran the unit this weekend and it tripped. I plugged the block heater back in and tried it 6 hours later and it tripped. Left the block heater plugged in and the next day ran it with no trip. Ran it later on with no trip. Ran it once a day the next 2 days with no trip. Whatever is happening seems to be heat related. The unit does get fairly warm when heater is plugged in. any thoughts. Thanks Mike
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cookelec
There is a terminal strip in the enclosure. Make sure all terminals are tight and not corroded. The RPM sensor wires go to that terminal strip before they go to the C&L board.
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Mikesterling
Replaced Latch board, ribbon cable and alarm relay. Problem appears to be gone. Time will tell. I want to thank all who answered my questions and guided me through the diagnoses process. These older units don’t tell you whats wrong and it takes people with skill who understand them.

Thanks Mike
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