Outdoor Power Equipment and Small Engines - Recharging generator field

Have a Honda EM5000S Generator. Has no more than 1 Hr's use. Was getting it ready to use this winter and cranks and runs perfectly, but AC power doesn't work. Took the front panel off, but can't see any burnt wiring or corrosion. It's kept inside of a screen in porch. On this model there isn't a re-set switch on the front panel. Any ideals of what happened? If's like new and was working last year for the short time I used it. Thanks in advance for anyones help?

How old is it? I know you said it was like new, but if the Field has lost it's polarity, it will not generate. Any electric motor shop should be able to re-polarize it if needed for little $$.

I Purchased it in 1996.

AC generators depend on a very small residual magnetic field remainng in the metal of the winding frame to build up a stronger field when energized. Sometimes that residual field is lost. You have to "flash the field" when that happens. If you can find the leads labeled F+ and F- connect a D cell battery between those two connections plus to F+ and minus to F- while the engine is running. You only need to be connected for an instant. See if the generator starts working after that. If not, then you may have other internal problems with the regulator. I've done the same operation to large 250 CAT powered diesel generators just fine with a small lantern battery and it works every time. There's a good chance that's all that's wrong with your generator.

Jughead, PLEASE FORGIVE, I didn't make myself plain, You stated Electric Generator, This is a Gasoline Generator, If that makes any difference, I'm not familier with generators.The one I have can be located at:
http://www.hondapowerequipment.com/ModelDetail.asp?ModelName=em5000S
I would take it to a dealer, but it's extremely heavy and is setting on my back porch, but if you think that would be better I'll do it.
Thanks so much!

Neil,
Jughead was using "generator" meaning the component in your gasosline engine Driven generator. They all operate under the same principles. Your generator as a unit contains a component which when driven will "generate" electricity, I believe this is what Jughead was making reference to ;)

Correct. The 'generator' part makes the electricity. That part doesn't care how it's turned. It could be done by a diesel or gasoline engine, a gas turbine or steam engine, or even by horses or oxen. In some places the 'generator' is turned by a water wheel. By your post, I presume that the engine starts & runs fine, but you get no electricity being generated. Sorry for the confusion. The place to start is to flash the field to see if that's the fix. A lot of the time that will be all that's necessary. In your situation the field may not be easy for you to recognize because the leads may NOT be marked. If that's the case you just have to go by experience. When experience is limited you just have to call upon more expert help. Since I'm here, and the equipment is there what I'm telling you is only my GUESS as to what may be wrong based upon my experience dealing with many, many sick generators, some very large and some small.

Thanks for your kind help, I really appreciate it. I'll see if I can locate someone to tell me which is + and - or I will take it to the shop.
P.S. This is a FANTASTIC FORUM

I try to learn something new every day, and Jughead your it for today. I never knew how to jumpstart a dead field.

If you try flashing the field yourself, there's one more thing to be aware of. Doing so will produce a momentary pulse of high voltage. Some of the larger generators that I've flashed have quite of bit of inductance in the field winding and when you break the connection with the battery there's usually a good size arc generated when the magnetic field collapses. I know that I've been jolted a couple of time messing around with smaller solenoids & a battery when I was younger, and a generator field is a simular situation. I've never been injured, but I've seen some impressive sparks. It impresses who ever is watching as well and scares them out of trying the same thing. I suppose you should be thankful for the steady work. It's always impressive when a large 500 KW diesel generator comes to life by using a small 6 volt lantern battery. I've even seen some generators with a built in swith for that very function, but the CAT service manuals have a proceedure using a small battery & resistor. So far I've never bothered with the resistor.

Boy, that puts my little 13k generator to shame.

hi jughead... i am having the same trouble with a small coleman powermate 1500 generator.... does the f+ & f- with a d cell battery apply to a very small generator as well? any idea where i would find the f+ & f- wires on this unit? in the area of the main windings or front switch panel? sorry about all the questions, i have never (YET) tinkered with a generator lol.... also, do these little buggers have brushes that may be needed & are they difficult to install?
thanks in advance

You may not be able to find separate F+ or F- leads coming out of small generators. Working on generators much smaller than 200 KW isn't something I generally do. However, I happen to own a 2000 watt generator made by Dayton and sold in the Graingers catalog. It was used for a project I built years ago and don't use much anymore. I checked that generator and here is what I found. The field part rotates and is energized by a set of brushes and slip rings. Power for the field comes from the stationary coils as does the output power. Since the field requires DC there's a diode bridge that rectifies the AC before it's sent to the brushes. In my generator the brushes can be gotten to, but I would have to dismount the diode bridge to determine which brush is plus and which is minus. I would then have to solder or carefully use clip leads to connect to the field. If you aren't sure just what you are doing, and aren't familiar with diode bridge rectifiers then the project most likely isn't something you would want to 'do it yourself.' Many 'do it yourself' projects require some level of knowledge and/or experience with simular technology to be successful. Many of the generators that I've worked on in the past used rotating rectifiers and are truely 'brushless'. The field leads coming out of the generator are, in fact, field leads for the generator's exciter, not the generator itself. I would assume that most small generators don't go to that extreme and just use a slip ring/brush setup. I would make that assumption unless your generator says 'brushless' somewhere on it. The big ones do.

It's always best to understand the basics of just how a generator makes AC power in the first place. When you understand how something works you have a real good chance at fixing it when it's broke. If there's no understanding, you are just 'shooting in the dark' and trusting to luck to resolve your problem.

Hi jughead!
Sorry so long to reply. I appreciate the time you took to look at your generator & explain (GREAT DETAILS) what you saw & what I might look for as well. I did see what looks to be two diode bridges. I also found an 800# for tech. support on the unit when I was taking it apart. So, I thought I'd wait untill Monday to call the support # rather than TRYING to remove diode bridges, maybe make a mess, & probably waste a lot of time & $$$ too! LOL

Soooo, Monday comes & I call... The tech. guy (Jim) @ Coleman was very helpful too. To flash the field on a small home use generator, I was told to get an ext. cord & cut off the female end of it & strip the wires & connect the wires to a 12 volt car or lawn tractor battery, & plug the male end of the cord, into the 120 A.C. side of the generator.

I was told to make SURE that the black wire which is POS/HOT on an A.C. cord, gets connected to the RED/POS. side of the auto battery, & the white wire on A.C. cord gets connected to the BLK./NEG. side of the battery. If the ext. cord wires are not black & white, then the smaller prong of the plug is the POS./HOT

Plug the other end of the ext. cord into the generators 120 volt side & remove spark plug wire, & pull the starter cord 4-5 times, then remove the ext. cord, reconnect the spark plug wire, start the unit & plug something of 120 A.C. volts in to see if it works & IT DID!!!!!! I then let it run for about a half hour with 2 300 watt lights to help re-generate the unit.

Thanks again so much for your help :)

Great. Thanks for the reply. I'll pass that proceedure along, when necessary, when others have problems with small generators. I can see why it should work. It was a lot easier doing it that way than the one I had in mind. Mostly I was familiar with the proceedure outlined in the CAT manuals for their large, mostly brushless, generators and have sucessfully followed it many times will good results. It would probably work for large generators as well if you could be sure the engine wouldn't start when you cranked it over with the starter. The main idea is to artificially produce a residual magnetic field so the generator can bootstrap itself up to produce electricity. No magnetic field no output...no output no magnetic field. If there's no residual magnetism you have to produce just a little with a battery for the cycle, which feeds on itself, to get the generator to work again. I frequently learn something new on here and today was no exception. It works as well to excite the armature as it does to excite the field when the residual magnetism is lost.

I've edited the title of Niel's first post to make it easier to find in the future.

Jughead and Nascar,
Kudos to both of you. This thread is a perfect example of why I browse this site whether I have a problem or not. The solution that Nascar found and shared is so beautiful, and requires no disassembly to implement. I have learned another useful process that I would never have learned otherwise. I am old enough to remember having to "Flash" the field on old generator equiped cars but never thought about it on current portable generators. Thanks again for filling another void in my grey matter. It is great fun to learn things about equipment I didn't know before. :)

You my have a problem with the voltage regulator. If it quits you won't have any AC power

By using a drop cord and hooking it to a battery. Plugging it into the AC outlet. Does this work for generators that have brushes or without brushes?

Hey, I just tried that Flash Charge the Field trick on a friends 4KW Coleman Generator and it worked like a charm.

We had checked all the windings, brushes, diodes, and connectors and everything had checked good but it still did not work. Took out the spark plug, plugged in a power cord, hooked it to a 12V car booster battery, gave it a few pulls, put everything back together and she fired right up and lit up a light bulb like it should. Many many thanks to Jughead and Nascar for the most excelent and useful suggestions.

From what I understand, with or without brushes the trick should still work just fine with just about any generator. It is mostly just random chance that will leave a field without enough residual magnetism to get things running. They should insert a permanent magnet in the rotor at the factory to prevent that from happening, but I guess it's just another one of those planned obsolecence feature things.

Steve

The manual on my generator clearly states that the unit should be run _under load_ at least once every 60 days or the generator may loose it's field charge.

Simple solution, I run it on the first weekend of every month for about 20 minutes.