MEP-804A A5 Governor Tests

[FLCarguy]

Hi all,
I have a question about a test in the maintenance manual, TM 9-6115-643-24 Section 4.2.1 test B. I will try to add a screen shot. This test is testing for voltage between terminal 19 and 20 on A5. The test states after hooking up the leads...... "then move the master switch to START position, reading should be battery voltage when generator does not crank, if there is no voltage between the terminals positions, the (GCU) A5 is not functioning properly and should be replaced."

My question is, when the S1 master switch is in start position I thought it was cranking? Does it mean after the relay turns off and it is running even though you are holding it in start? What mine does is when you turn to start I have battery voltage at 19 and 20 for a very short time, about 2 seconds then nothing. (even if holding the switch in start) The note does say there will be no voltage there when the unit is running so that makes sense but the statement above from the manual makes no sense to me.

 

[Evvy Fesler]

May I ask why you suspect there is a governor problem?

 

[FLCarguy]

May I ask why you suspect there is a governor problem?

Hi,
Sorry for the delay I was out of town. I don't necessary think I have a governor problem. I have no Freq and and no Voltage so I am following the TM troubleshooting again and this is one of the first test.

A little history,,, after going through it this set ran fine for about a year. Then I suspect it got hit by lightning as there is a huge black spot on the top and all the paint is peeled back about a foot! I did not see this at first as it is on a trailer and I don't normally look at the top of it so I tried to start it as a test as I do every month and it would just overspeed and shut off. I troubleshot that down to the governor control circuit of the actuator. Specifically the transistors that control the voltage to the actuator. While I had the governor out I was poking around and notice my voltage regulator was also smoked. So I bought an aftermarket new one from someone here. Put that in, and was able to see the gauges jump on startup with the old governor so I assumed that was all good. I then replaced the governor and now the generator starts, runs great, I can adjust the speed with the freq pot, but the freq and voltage gauges don't budge. I don't suspect the voltage regulator as it is new but it is the next thing to test. I also went over every harness and connection in the machine as well as relay bases to see if anything else was toast but all seem ok.

 

[robertsears1]

Have you verified at the lugs with a meter that there is no voltage? For frequency backup, you can buy a Kill-a-watt meter that plugs into the duplex plug from Lowes. On my 804s, I believe I have always gotten the voltage and frequency readings over the last 10 years but it is always a crapshoot on my 003/002 if the gauges will work today. I do make sure to exercise the AM-VM switch several times each run to wipe the contacts.

 

[FLCarguy]

Hi,
Yes, I work on industrial mechanical/electrical machinery for a living so I have scopes and meters and analyzers galore! lol. I don't however work with generators so this is a learning experience but I like it. I do have frequency at the service outlet and can adjust it with the freq pot, on the governor itself and the pot on the front panel. But the voltage is very low, like 12vac which I assume is the exciter or the coils themselves just generating some voltage. I do not have any lights or faults other than undervoltage. I do trust the gauges however as they were working fine a month or so ago.

 

[robertsears1]

Silly question since you said it ran fine for a year. If you read the starting instructions under the flip up panel carefully, you will notice that it says to hold S1 in start until you see at least 25 psi on the oil pressure gauge. You can sometimes get an under voltage light if S1 is released to quickly. It was a hard habit for me to break letting go too quick on startup. These crank differently that anything else I have ever started since you can hold it in start well after it is running. My 003 requires 14” of holding in start after running to satisfy the oil pressure interlock.

 

[FLCarguy]

Hi,
Yes, that is a very good point, however I have been down that road as well, lol. It does not matter how long you hold it down you get no voltage. I have seen that some people had a problem where they had voltage when they held the switch over but it would go away when they went back to run. It does not matter how long you hold this switch, I have no voltage in start or run. Even did the battle short trick and disconnected the fault panel but still no joy.

 

[loosegravel]

Hello, I'm dealing with a similar problem on the same unit. I'm just wondering what ever became of this? Were you successful in getting it repaired? Thanks, Jeff