MEP003a Unstable Voltage

[jamawieb]

Go back to the VR. You had 70 volts before turning the pots on the VR, after turning them you have nothing. Even with the spark you saw, I still say its the VR.

 

[Lukes_deuce]

Im going to investigate where to find the exciter wires. I would like to rule it out before I order a new VR. I hope its the VR so I can put these gremlins to rest!

 

[jamawieb]

If you look at the back of the distribution box (Where the lugs are) you will see 4 wiring harnesses in the back. The smallest with 2 wires should be the exciter wires going to the generator head. You need to take the cover off the back of the generator head and you'll be able to see the exciter.

 

[Lukes_deuce]

Got out to the genset today. Took off the back cover off of the generator head and looked the excitor wires. Every thing looked intact. I poked around and no broken wires. I blew out the generator housing. Lots of dust and dirt hiding in there. I started her up and no voltage. I checked pin 27 on the starter switch and I had 23 volts when I turned the switch to start when the unit was running. I attached some pics of the end of the generator. What do I look for next?

One other question. My voltage selection switch on the front main panel is stuck. Would this make a difference on the unit making power?

https://youtu.be/Ijw1WJuQhCE

 

[jamawieb]

Take some wd40 and spray it all over the switch where all the wires connect inside the distribution box. Then lightly tape on the switch, while trying to turn the switch, it will eventually free. When it is free, rotate it several dozen times and see if that helps your situation.

 

[Triple Jim]

Is that mass of corrosion really your rotating diodes? I can't imagine they're making contact with the metal bracket properly. In fact I'm having a hard time believing they could work at all, looking like that.

 

[Guyfang]

Like Triple Jim, I believe your problem may be the diodes. I can easy see a spark when the exciter voltage jumps from one pile of corrosion to the next there.

 

[Lukes_deuce]

I went out early this morning and doused the AC voltage switch with wd-40. I got the switch to work as intended. I didn't have a chance to start up the unit since it was early on a sunday.

What do you guys suggest with the diodes? Clean them up with some baking soda? Or are they shot?

 

[Triple Jim]

If that were mine, I'd unbolt the diodes from the mounts, do whatever it takes to clean the corrosion off the mounts, clean the diodes, check the diodes with a meter to make sure they're good, put a thin coat of grease on the mounts and diode threads, and bolt it all back together, and verify good electrical contact between the diodes and the mounts. I'd fully expect that job to be a big pain, too.

 

[Lukes_deuce]

If that were mine, I'd unbolt the diodes from the mounts, do whatever it takes to clean the corrosion off the mounts, clean the diodes, check the diodes with a meter to make sure they're good, put a thin coat of grease on the mounts and diode threads, and bolt it all back together, and verify good electrical contact between the diodes and the mounts. I'd fully expect that job to be a big pain, too.

Thanks for the advice Jim. Its not a hard job but tough to get too. The bottom set will be very difficult to access. What should the diodes register? How many ohms?

I'll try and work on it this week. As long as the temps are not too cold.

 

[Triple Jim]

Test diodes with the diode test function of a multimeter, not the ohms scale. If unsure, check your meter's manual. Even if working on the diodes doesn't cure the problem, it will almost certainly prevent a future one.

 

[Lukes_deuce]

Ok gotcha. I doubt I have that on my meter. I'll have to ask my electrical engineering buddy.

 

[Guyfang]

I check diodes with a multi meter. Use the continuity function, or if your meter has a diode function, use it. You get continuity in one direction, and not in the other.

 

[Triple Jim]

With a meter that doesn't have the feature built in, you can power a 12v test lamp through the diode and see if it lights the bulb one way but not if you turn the diode around the other way.

 

[GREENMV]

Smart

With a meter that doesn't have the feature built in, you can power a 12v test lamp through the diode and see if it lights the bulb one way but not if you turn the diode around the other way.

 

[Lukes_deuce]

I have all the diodes unbolted from the brackets. Its been really tough with the multi-meter to determine if it's bad or not. I'm going to try the light bulb method now. Do all the diodes the test same way? Have the light on the nut end of the diode and apply 12v to the wire feeding the diode?

 

[Lukes_deuce]

This is how I'm testing them. Some times it works, some times it doesn't.

 

[Lukes_deuce]

Since the ohm meter was not accurate for me, I went ahead with the light bulb test. I applied 12 volts to each side of the diode and used a 12v test light to check the other side of the diode. Here are my results:

Diode 1 - Power on wire, light on threads
- Power on threads, NO light on wire
Diode 2 - Power on wire, NO light on threads
- Power on threads, light on wire
Diode 3 - Power on wire - NO light on threads
- Power on threads, light on wire
Diode 4 -Power on wire, light on threads
-Power on threads, NO light on wire

Im hoping 1 & 4 and 2 & 3 are grouped together. If looking towards the generator head, 1 & 4 are the left half of the unit and 2 & 3 are the right half. Any thoughts would be greatly appreciated since this is all above my electrical knowledge. Thanks!

 

[Triple Jim]

Sounds like the ones you tested are good, but there are three of each. Even if they all test good, it's still possible there was corrosion at their mounts, and cleaning everything before assembly could fix things.

 

[Lukes_deuce]

Hey Jim, thanks for the info. Where are the other ones? The wiring diagrams leave a lot to be desired

Sounds like the ones you tested are good, but there are three of each. Even if they all test good, it's still possible there was corrosion at their mounts, and cleaning everything before assembly could fix things.