My ONAN 5500 finally fixed
As some might know, have been having problems with my Onan for years, ever since I got it.
Started with checking fault codes, they translated to needing new carb, to get it running at all. Tried to clean old carb to no avail. It did get better, but still not right.
Some of Those fault codes couldn't be any more vague or harder to interpret for the layman not familiar with Onan's.
Installed a new carb. Adjusted/set up the HZ, checked it under full load, it was perfect.
New carb seemed to do the trick, for a day or so.
Then I noticed the gen would run for maybe 1-5 hours perfectly, then quit. It would restart immediately, then usually shut right back down in minutes. If I waited a hour or so it would run again for a while.
Don't get me wrong, when it was running it ran flawlessly. It just stopped running randomly, sometimes after running under full load, 2 a/c on for hours. Sometimes it would run for a full weekend trip, starting and stopping correctly whenever needed, no problem.
Did a full gen service, oil, filters, etc, many times. Gen had 24 hours on it when I got it. It now has 427 hours.
Seemed like whenever the fuel got less than 1/2 tank, the problem would arise.
Tried the gas cap off vent the tank thing, no change.
So tried a new fuel pump. No change.
Tried a can of gas connected directly to the fuel pump with 3' of tubing, bypassing the fuel tank and its fuel supply line. No change.
So as you can see, this was an intermittent problem. But a problem none the less. The gen would stop at the worst times possible. Like on a hot night early fall at the dunes. With both ac running and just cooked a nice big dinner. 8 of us just sat down to eat, wouldn't ya know it, yup the gen quit, no more ac.
This type of intermittent problem went on for 2+ years...
I Couldn't figure it out.
Then started noticing when the gen would shut down. It seemed to happen shortly after I turned off the load that was on it. Or when the load would cycle or change. Like when an ac would cycle off, on the thermostat. Or the microwave would shut off. And the battery charger/converter had already fully charged the batteries.
So this got me thinking, and went back to basics. Checked the fault code again. hadn't done that since I replaced the carb. Should have. It came up different from the the carb failure problem in the beginning. It was now fault code... 'unable to maintain frequency'.
So whipped out my handy meter, set it to HZ and found 62.7hz. Well, it is suppose to be 60-63hz per the manual. But it was running under load with 1 ac, tv, and converter using ac power. I shut down all loads and then hz started rising, went to 67 or so... then it shut down... Started it back up and immediately started the ac so it stayed running, it ran again at 62.5 under load.
Hmmm, we're getting somewhere now. After some reading in the manual and online, found out the control turns off the genny at 67-68 hz as to not damage anything from to high HZ.
So now it was time to readjust my HZ like I did when I changed the carb. Was sure I had set it right to start with a couple years ago..? I doubled triple checked checked it back then...??? Hmmm maybe something wore out or changed...
Started to turn the nut that adjusts the governor spring/arm to lower rpm thus lowering the HZ. With my meter right next to me, and gen running under low load, with the converter and microwave on it was at 63.7, to high, so I kept on turning the nut and the hz lowered a little, about maybe 1.5 hz, but it wouldn't go any lower even though i kept on turning the nut... Then I saw it, the wire from the choke was under the arm holding it from going lower. As soon as I moved that wire out of the way, the hz went down to 57. I adjusted it back up to 62. Then proceeded to do the correct hz adjustment procedure with load and without. Ended up with 59.5hz with both ac, and microwave on. With no load on it, it was at 62.5... perfect.
It hasn't missed a beat or turned of since. And the 'fix' was on my Halloween dune trip. Have been out 3 times since then and for 7 days over the New years. It doesn't shut down intermittently any longer.
Guess my attention to detail when the carb was replaced originally was less than enough. At full load that wire wasn't close to holding the arm up. What I didn't realize, was that arm moves quite a bit, and that wire can't be anywhere close to the arm, or it will hold up the arm not letting the rpm drop enough when the gen off loads.
Just thought I'd pass this along in case anyone else has a similar problem. Check your choke wire and get it far far away from that governor arm...
Started with checking fault codes, they translated to needing new carb, to get it running at all. Tried to clean old carb to no avail. It did get better, but still not right.
Some of Those fault codes couldn't be any more vague or harder to interpret for the layman not familiar with Onan's.
Installed a new carb. Adjusted/set up the HZ, checked it under full load, it was perfect.
New carb seemed to do the trick, for a day or so.
Then I noticed the gen would run for maybe 1-5 hours perfectly, then quit. It would restart immediately, then usually shut right back down in minutes. If I waited a hour or so it would run again for a while.
Don't get me wrong, when it was running it ran flawlessly. It just stopped running randomly, sometimes after running under full load, 2 a/c on for hours. Sometimes it would run for a full weekend trip, starting and stopping correctly whenever needed, no problem.
Did a full gen service, oil, filters, etc, many times. Gen had 24 hours on it when I got it. It now has 427 hours.
Seemed like whenever the fuel got less than 1/2 tank, the problem would arise.
Tried the gas cap off vent the tank thing, no change.
So tried a new fuel pump. No change.
Tried a can of gas connected directly to the fuel pump with 3' of tubing, bypassing the fuel tank and its fuel supply line. No change.
So as you can see, this was an intermittent problem. But a problem none the less. The gen would stop at the worst times possible. Like on a hot night early fall at the dunes. With both ac running and just cooked a nice big dinner. 8 of us just sat down to eat, wouldn't ya know it, yup the gen quit, no more ac.
This type of intermittent problem went on for 2+ years...
I Couldn't figure it out.
Then started noticing when the gen would shut down. It seemed to happen shortly after I turned off the load that was on it. Or when the load would cycle or change. Like when an ac would cycle off, on the thermostat. Or the microwave would shut off. And the battery charger/converter had already fully charged the batteries.
So this got me thinking, and went back to basics. Checked the fault code again. hadn't done that since I replaced the carb. Should have. It came up different from the the carb failure problem in the beginning. It was now fault code... 'unable to maintain frequency'.
So whipped out my handy meter, set it to HZ and found 62.7hz. Well, it is suppose to be 60-63hz per the manual. But it was running under load with 1 ac, tv, and converter using ac power. I shut down all loads and then hz started rising, went to 67 or so... then it shut down... Started it back up and immediately started the ac so it stayed running, it ran again at 62.5 under load.
Hmmm, we're getting somewhere now. After some reading in the manual and online, found out the control turns off the genny at 67-68 hz as to not damage anything from to high HZ.
So now it was time to readjust my HZ like I did when I changed the carb. Was sure I had set it right to start with a couple years ago..? I doubled triple checked checked it back then...??? Hmmm maybe something wore out or changed...
Started to turn the nut that adjusts the governor spring/arm to lower rpm thus lowering the HZ. With my meter right next to me, and gen running under low load, with the converter and microwave on it was at 63.7, to high, so I kept on turning the nut and the hz lowered a little, about maybe 1.5 hz, but it wouldn't go any lower even though i kept on turning the nut... Then I saw it, the wire from the choke was under the arm holding it from going lower. As soon as I moved that wire out of the way, the hz went down to 57. I adjusted it back up to 62. Then proceeded to do the correct hz adjustment procedure with load and without. Ended up with 59.5hz with both ac, and microwave on. With no load on it, it was at 62.5... perfect.
It hasn't missed a beat or turned of since. And the 'fix' was on my Halloween dune trip. Have been out 3 times since then and for 7 days over the New years. It doesn't shut down intermittently any longer.
Guess my attention to detail when the carb was replaced originally was less than enough. At full load that wire wasn't close to holding the arm up. What I didn't realize, was that arm moves quite a bit, and that wire can't be anywhere close to the arm, or it will hold up the arm not letting the rpm drop enough when the gen off loads.
Just thought I'd pass this along in case anyone else has a similar problem. Check your choke wire and get it far far away from that governor arm...
