Any ideas on Powertech generator not always producing power? (Again)

gus · June 27, 2012, 02:15:19 PM

Sticky brushes will do it. Let's hope it is that simple.

I had the same problem of getting to the head with my Westerbeke, had to pull it out at an angle so get to it.

belfert · June 27, 2012, 03:41:57 PM

An even bigger pain is the fact I have to unbolt the generator mounts and then raise everything up an inch or two to get to all the bolts to remove the end of the head. I could really use an engine hoist, but I don't have one. I guess I better get to work.

gus · June 28, 2012, 12:29:20 PM

I just lost this post to the site gremlins!!

I used pry bars and thin boards to lift mine. There is a lip on the outside edge I had to slide it over. I have a hoist but a hoist requires way too much overhead space even to hook it up, never mind lifting it.

I used a come-along and nearby tree to slide it out. Helps if you live in the boonies with lots of trees! I slid it onto a 1000 lb capacity flatbed wagon I got from Harbor Freight and hauled it away.

I also considered splitting the head cover before re-installing it so it could come off in two pieces. I may do this yet if I re-install it but for now I'm going with the little Honda and using the diesel for a house backup.

If your rectifier is inside the head like mine you may want to do this. Yours probably is inside the controller box, a much better place for it.

TomC · June 28, 2012, 01:37:42 PM

My 10kw Powertech is brushless. I guess the smaller gensets have exciter brushes. My genset is in a very tight compartment-so small the radiator is remote mounted with a 1/2 hp 2spd squirrel cage blower. To ventilate the gen compartment, I use from grainger an 8" inline bathroom ventilator (it can take moisture) that puts out 250 cfm. The fan blows directly on the alternator end so to get the coolest air. I have loaded up the genset and after an hour, I can still put my hand on the alternator head because of the good ventilation. Keeping it cool is important. Good Luck, TomC

belfert · June 28, 2012, 03:37:37 PM

My rectifier is actually mounted outside of the generator enclosure at the top of the unit.

belfert · June 28, 2012, 06:11:39 PM

After mulling it over some more I realized the best course of action would be to pull the entire unit out. The problem is I can't lift from the bottom of the generator head or the bottom of the engine. I need to lift from the top and I'm not sure I have enough room for an engine hoist.

I called my buddy who originally installed the generator with his forklift and he is going to stop by on his way from work tomorrow to look at it. I suspect we'll end up taking the bus over to his house to lift the generator out with the forklift and then use the forklift to lift the engine up so the generator end is clear to take the end cap off. The generator is all disconnected except the fuel lines so we can have it out in 10 minutes or so.

gus · June 29, 2012, 03:07:21 PM

Be sure to keep us posted on how this turns out, very curious!!

TomC,

My 7.7 diesel Westerbeke is excited by the rectifier which depends on a small AC voltage to excite the field. I presume residual magnetism is what gets the whole chain started and the reason they sometimes have to be flashed since this mostly restores the residual magnetism plus ensures the correct polarity.

AC output is taken directly from the brush rings on the rotor.

As I remember, one of the diagnostic tests is to apply 12V DC directly to the field, bypassing the rectifier, and this produces around 70 V AC if the field is OK. Don't hold me to this because it is from memory of the stuff I did two months ago!

belfert · June 29, 2012, 03:21:32 PM

Success! My friend who repairs forklifts for a living came over and looked at the generator this evening. He works on a lot of large electric motors in his line of work. He determined that just the wire mesh could come off and we could get to the brushes that way. No need to pull the end of the head which would require lifting the motor up.

The Powertech tech was right and the brushes are sticky. One brush is worn way shorter than the other one and it was stuck. I'm surprised the generator made power at all. A new set of brushes and I should be on to the next repair.

Oonrahnjay · June 29, 2012, 03:53:28 PM

Quote from: belfert on June 29, 2012, 03:21:32 PMSuccess! (snip)
The Powertech tech was right and the brushes are sticky.

Glad to hear that, Brian. Sorry that it was such a PITA to get there, but you learned things along the way.

luvrbus · June 29, 2012, 04:18:04 PM

I would spend the 60 or 70 bucks and replace whole brush assembly Brian,all the Powertech I have been around have brushes for the exciter are you saying your doesn't TomC ?

good luck

belfert · June 29, 2012, 04:34:46 PM

Quote from: luvrbus on June 29, 2012, 04:18:04 PM
I would spend the 60 or 70 bucks and replace whole brush assembly Brian,all the Powertech I have been around have brushes for the exciter are you saying your doesn't TomC ?

I am going to replace the entire assembly. I don't even know where I would get the individual brushes. I can't even get the brushes out of the assembly.

At least I didn't wait until the last minute to start looking at this. I really have no other repairs to do besides take another look at the ABS system.

bobofthenorth · June 29, 2012, 06:24:34 PM

Quote from: belfert on June 29, 2012, 04:34:46 PM
........... I really have no other repairs to do besides .........

Oh boy - I would never make such a claim even to myself, let alone in public. You are really asking for a karma smackdown. Hope it works out for you.

zubzub · June 30, 2012, 05:45:46 AM

Quote from: bobofthenorth on June 29, 2012, 06:24:34 PM
Quote from: belfert on June 29, 2012, 04:34:46 PM
........... I really have no other repairs to do besides .........

Oh boy - I would never make such a claim even to myself, let alone in public. You are really asking for a karma smackdown. Hope it works out for you.

gus · June 30, 2012, 03:07:56 PM

Glad to see it was such a simple thing.

However, I go along with the other guys - it isn't over till it's over!!

You also need to check the rotor ring for the one brush worn more than the others, it may be faulty or, at the least, have a rough spot that needs to be smoothed. Brushes usually last for years and years.

Does it have four rings?

Keep the old brush assembly for spare parts. Unless these are really odd-balls replacements are usually easy to find at any electrical supply business. Manufacturers don't usually try to reinvent common parts even though they often use their own part numbers and charge triple the original price!

belfert · June 30, 2012, 03:47:11 PM

The generator head is a Marathon pancake generator head. Unfortunately, made in China. Would any old electrical supply house have the brushes? What about a electric motor repair place?

I'm sure the reason the brushes got sticky is the amount of dirt everywhere. I vacuumed up at least 1/2" of fine dust from all around the generator. I also blew out a lot of dust from the whole unit.