How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14406
Experience:  Certified on Onan and Generac generators
Type Your Small Engine Question Here...
Hank F. is online now
A new question is answered every 9 seconds

I have a mitsubishi mge 5800 generator. The engine starts fine

This answer was rated:

I have a mitsubishi mge 5800 generator. The engine starts fine and runs good, but does not generate power. The power will either go to 120 V briefly, or not start at all. I just changed the brushes, this did not help. The generator is about 5 years old and has about 300 hours of light usage. Any help greatly appreciated.


Do you have a good multi meter available?


I have a service manual for this unti, which is very detailed. I can upload it for you if you wish, or I can walk you through the steps for troubleshooting. Just let me know.


The most likely problem is a bad voltage regulator.

Customer: replied 6 years ago.
Yes, I have a good multi-meter. I have the basic operating manual, I don't know what I am looking for.

OK, I am going to go on the assumption that it is a bad voltage regulator. I am going ot give you a series of tests, and what the normal results of those tests should be. At any time you get a result significantly different than what it should be, stop and let me know. We are actually going to test all components to make sure they are good. I do not like changing parts unless I know they are bad.


First, remove the brush cover. disconnect the wires going to the brush leads and ohm across the brushes. You should get 6-7 ohms.

Place one meter lead to one of the brush leads, and the other meter lead to the frame of the set. You should get no continuity.

Reconnect the wires and set your meter to VDC. Place one probe of the meter to each brush lead and start the set. You should get 12-20VDC. Stop the set. Disconnect the wires again.

Remove the control panel and locate the voltage regulator at the back of the control box. It will have a 6 wire connector with the wires being red, white, brown, light green, and 2 yellows. Unplug this connector.

If you have electric start, you can use the battery on the set. If you have a manual start, you will need a 12V battery. Make up 2 jumper wires about 3ft long, and attach a connector the same size as the spades on the brush leads to one end of each wire. The brown wire is the positive brush, and the light green wire is the negative brush. Attach one of the jumpers to the positive brush and the positive post of the battery. Attach the other wire to the negative brush. Start the set and attach the wire from the negative brush to the negative terminal of the battery.

Go back to the 6 pin plug that you just removed from the voltage regulator. Set your meter to VAC and connect the leads across the following pairs of wires:




Red to white should be 110-126V.

White to light green should be 122-142V.


If these all check OK, your voltage regulator is bad.

Please let me know what you find.

Customer: replied 6 years ago.
Sorry for the delay, I ran the checks you suggested.

The brushes are reading about 10 ohm (I checked between runs was 10.2,7.5,10)
Brush to frame was 135 megaohm... no continuity.
With the wires connected my meter was reading -1.3V DC with the negative lead on the green brush.
The connector from the AVR had four wires in the connector, the two yellows were separate, I only unplugged the four.
White to lt green was 114VAC
Red to white was 110VAC
The battery I was using wasn't fully charged (12.3V)

No problem, it is a busy time of year for everyone.


With the tests you ran, the results are consistent with a low battery. By manually exciting the field (jumping the 12V), we have proven that the rotor and stator windings are good. The set will produce electricity when voltage is applied to the brushes. The problem is that the voltage going to the voltage regulator is not being rectified to DC to excite the field, so that means the voltage regulator is bad. Replace the voltage regulator and you should be good to go.


You will be able to order one directly from Mitsubishi.

For Parts and Service, please contact Mitsubishi Engine North America, Inc

Hank F., Technician
Category: Small Engine
Satisfied Customers: 14406
Experience: Certified on Onan and Generac generators
Hank F. and other Small Engine Specialists are ready to help you

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

  • You did one super job of explaining to me everything there is to know about this fridge. I'm looking forward to asking you questions in the future. Jimmy Bagley, IA
< Previous | Next >
  • You did one super job of explaining to me everything there is to know about this fridge. I'm looking forward to asking you questions in the future. Jimmy Bagley, IA
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland

Meet The Experts:

  • Curtis B.

    Curtis B.


    Satisfied Customers:

    have worked on and around most engine models for 35 yrs./Polaris ATV expert
< Last | Next >
  • Curtis B.'s Avatar

    Curtis B.


    Satisfied Customers:

    have worked on and around most engine models for 35 yrs./Polaris ATV expert
  • Rick's Avatar


    Factory Authorized Trainer

    Satisfied Customers:

    Outdoor Power Equipment technical trainer since 1990, covering eight states.
  • Jon K.'s Avatar

    Jon K.

    Small Engine Diagnostic Expert

    Satisfied Customers:

    Gold certified Stihl tech, Service Manager for a rental/repair shop.Certified in most small engines
  • James W's Avatar

    James W

    Small Engine Troubleshooting Expert

    Satisfied Customers:

    7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years
  • Vince O.'s Avatar

    Vince O.

    Small Engine Technician

    Satisfied Customers:

    Over 30 years experience repairing lawn and garden equipment. Chainsaws, mowers,blowers and trimmers
  • RUSS's Avatar



    Satisfied Customers:

  • Wayne's Avatar


    Engine Rebuilder

    Satisfied Customers:

    many years on egine rebuilding, lawn mower,roto tiller,Truck,and small engines