onan genny

Discussion in 'American RV's' started by ginge61, Aug 11, 2008.

  1. ginge61

    ginge61 Read Only Funster

    Joined:
    Oct 29, 2007
    Messages:
    431
    Likes Received:
    1
    Location:
    n/wales
    the genny runs ok but had it checked and its not puting out much more than 70-80 volts its a 4 k a genny checked the kh and that is fine at 60 is there anything that adjusts them etc it fitted on an 89 winne c class :cry:
     
  2. johnsandywhite

    johnsandywhite Read Only Funster

    Joined:
    Jul 29, 2007
    Messages:
    2,348
    Likes Received:
    15
    Location:
    Doncaster/Spain
    :Cool: The voltage should read between 110 and 120 volts depending on engine speed and load. It could be a regulator fault or the windings.

    But if everything works OK? Whats the problem?
     
  3. American Dream

    American Dream Read Only Funster

    Joined:
    Aug 20, 2007
    Messages:
    6,489
    Likes Received:
    154
    Location:
    Lincoln
    I'm assuming it's at the US 60 Hz.How was the voltage measured?

    I'm wondering if it's running at the correct rpm.

    Have you had that checked?
     
  4. ginge61

    ginge61 Read Only Funster

    Joined:
    Oct 29, 2007
    Messages:
    431
    Likes Received:
    1
    Location:
    n/wales
    ye thats correct a local sparky checked the volts etc
     
  5. ruffingitsmoothly

    ruffingitsmoothly Read Only Funster

    Joined:
    Jan 2, 2008
    Messages:
    1,395
    Likes Received:
    69
    Location:
    West of Southampton edge
    Hi found this if it is of any help

    On the trip to Palm Desert, my Onan was not putting out much voltage when a load was applied. When I had the water heater and the coffee pot going at the same time (under 3000 watts) the voltage would drop to about 100v. I tried adjusting the carb, the governor speed and sensitivity and got the voltage to finally hold at 110v with this load. However, I didn't go back and check the no load voltage. Unfortunately, I later discovered that my no load voltage was in excess of 150 volts (thats as high as my plug in voltmeter would display) and the result was that I fried my Statpower charger when I started up the Onan the next morning.

    The manual shows that if a high low voltage occurs when there is no load at 1800 rpm but the loaded condition has the proper voltage it is probably a bad "compounding reactor". So, I started working on the Onan with this as the premise. I quickly discovered that I would have to remove the whole brush end of the Onan to get at this part so I decided to see if I could test it while in place.
    It has a lead going to the bridge rectifier which is easy to get at by just pulling off the plastic cover under the lower rear part of the brush housing. While under the Onan I accidentally discovered that another lead going to the rectifier was very loose at a connection and would not hold together. There are two male/female spade connectors going from the field windings to the + and - terminals of the rectifier. Each set is in its own approximately 2" plastic insulating tube. They are made of brass and I found that there was very poor contact as the brass female connector had lost its tension. I attempted to squeeze it with some needle nose pliers and it immediately cracked. I then soldered in a new steel female connector, coated it with dielectric grease and plugged in back to the male connector in the tube. I checked the other connector and found that it also was making very poor connection and was also loose in the tube. I replaced that connector as well.

    Governor
    I next started the Onan and found that I had much higher voltage than before. I used a mechanical tach through the front flywheel cover hole and set the no load to 1800 rpm which corresponds exactly to 126 volts. I went through the various adjustments with the carb, the governor speed and the sensitivity and was able to get 126 volts at no load but it would still drop to about 110 with 3000 watts. That's about where is used to be and I figured that I would have to live with that and just turn the water heater off when I wanted to use the microwave as we had been doing for the last few years. I then noticed the paragraph in the maintenance manual about the linkage adjustment (from the carb throttle to the ball on the governor arm). I had never adjusted that so I decided to check it. Following the instructions, with the Onan off, I popped it off the ball joint and held the carb wide open against its stop and checked the end against the ball joint. I found the linkage to be about 1/4" too long. I rotated the end until it just fit over the ball stud. I then restarted the Onan and readjusted the carb and governor until I again had 126 volts at no load. I then started to turn on electrical equipment and found that the voltage never dropped below 120 volts. I started with the water heater, added the coffee pot, the air conditioner heat strip and even the microwave and it would still hold at 120 volts. I calculate that I had about a full load of 6000 watts on the Onan. It has never done this before in the 20+ years that I've had the GMC.

    I had never thought to adjust the linkage arm before. In fact, the factory paint was still on the threads when I turned the end to shorten it. It apparently had never been set properly by the factory.
    I also noticed that there are two more of the connectors in the same type sleeves on the left top of the Onan in the wires going to the fuel pump and to the solenoid. I checked these but they were tight. Apparently the heat from the engine and generator caused the lower brass field wire connectors to loose their temper and thus cause a loose connection.
    I would suggest that everyone check these two connectors and the carb linkage on their Onan. There was nothing wrong with the compounding reactor. I believe that my initial problem was occurring because of intermittent contact on the field windings.



    Regards Pat
     
  6. TJ-RV

    TJ-RV Deleted User

    Might be appropriate to post a summary and provide a link to the guy's web site rather than copy/paste his content. That would respect his copyright and comply with this forum's Terms Of Use.

    OTOH if you have his permission to re-publish his work, ignore the what I said.
     
  7. ruffingitsmoothly

    ruffingitsmoothly Read Only Funster

    Joined:
    Jan 2, 2008
    Messages:
    1,395
    Likes Received:
    69
    Location:
    West of Southampton edge
    So sorry guilty of trying to help a fellow RV'r:Blush::Blush:

    [​IMG]

    Regards Pat
     

Share This Page