This past weekend at the track my generator kept giving me issues and kept shutting off on me. It came up with trouble code 47. When i looked online it said the fix was to replace the circuit board. I have ordered a new circuit board from Flight systems p/n 300-5374. I don't see anywhere on how to do the job. Does anyone know if i have to pull the generator out of the trailer to do this or if i can get to the part from the front. I wasn't sure if it was behind the start switch or how much of a pain this job was going to be. Model number on generator is 7HGJAB-900D. I appreciate any help or advice.

I believe Flight has a video.

https://www.youtube.com/watch?v=aa8UHioQPlI

i saw that video but that 4000 isn't the same as mine.

The main man with the crystal ball. Rich. should be in shortly. He will tell you.

quote:

Originally posted by TD3550:
The main man with the crystal ball. Rich. should be in shortly. He will tell you.

your video did get me thinking. I just called flight systems and talked to their tech. Not sure why i didn't think about that haha. He said it wasn't too bad of a job. 2 10mm bolts on front of cover and one in the back thats a pain in the butt to get to. Once i get those off i can remove cover and get to the circuit board. Hopefully Rich will be able to tell me if that is correct.

quote:

Originally posted by TD3550:
The main man with the crystal ball. Rich. should be in shortly. He will tell you.

Here I is....

Control board is inside black box on left side behind where start/stop switch is

Remove B+ battery cable at red post in front of switch box......Disconnect it first from battery or tape it up...

Remove 1 10mm bolt front of black box.....lift it up and out...a mess of wires will be in there and it is a mess...

Rear black box has 3 10 mm bolts holding it down.....Remove locking connector first that goes into the existing control board...don't break the lock !! Lift up the tab and pull out.....

Remove 3 bolts.....2 are not visible.....left, right and one in back..

Black box comes out and board is mounted in there with 2 bolts....

Wiring is a mess but that's how they make 'em

If the board doesn't fix it and nothing changes you have a bad rotor.....usually a break in one winding where they attach to the slip rings.....

If that does happen you cannot buy just the rotor and have to buy a rotor and stator as a unit...

I do this job with my eyes closed ...lol

I also always just plug the board in and reconnect the battery and test it with the board hanging out loose.

I have boxes of good test boards for most machines......Makes it real easy to do a quick test and move on if the board is not the issue....

After re-reading your original post I think it very well maybe just the board.....The flight boards work fine ....

This message has been edited. Last edited by: SCDIV1,

What year/hours on Generator? or what causes these to fail? Mine works fine, but I like to be prepared...

Any Onan from 2001 and newer can have Control Board failures

They generally are ok for 2-3 thousand hours but time is also a factor....the older they are the hours doesn't matter.

Hot weather is when the issue shows up.
The hotter it is out is when they fail the most. Intermittent shutdowns and random fault codes....

Poor installs with no regard for the hot exhaust being drawn in on the cool air suction side kills these units....Cylinder heads fail and must be replaced...

Older models were completely different and had their own set of issues...

I just fixed an old black cover Marquis 7kw.....No ignition .....Mouse nesting inside causes a part failure.....I've don that job a lot in the past....those machines were the best thy ever made but had their issues as well.........They have not made those for about 20 years and parts are limited for those....


All the newer design machines have 1 single PC control board

The older machines like the black cover Marquis from the 1990's had 4 different electronic controls...and are even tougher to diagnose because of the multiple controls

I know all the behaviors and have lots of boards and even the G-Man test box sold by Flight.....Works very well but I think was over $500

Nothing beats some experience, some boards and a Fluke meter

quote:

Originally posted by SCDIV1:

quote:

Originally posted by TD3550:
The main man with the crystal ball. Rich. should be in shortly. He will tell you.

Here I is....

Control board is inside black box on left side behind where start/stop switch is

Remove B+ battery cable at red post in front of switch box......Disconnect it first from battery or tape it up...

Remove 1 10mm bolt front of black box.....lift it up and out...a mess of wires will be in there and it is a mess...

Rear black box has 3 10 mm bolts holding it down.....Remove locking connector first that goes into the existing control board...don't break the lock !! Lift up the tab and pull out.....

Remove 3 bolts.....2 are not visible.....left, right and one in back..

Black box comes out and board is mounted in there with 2 bolts....

Wiring is a mess but that's how they make 'em

If the board doesn't fix it and nothing changes you have a bad rotor.....usually a break in one winding where they attach to the slip rings.....

If that does happen you cannot buy just the rotor and have to buy a rotor and stator as a unit...

I do this job with my eyes closed ...lol

I also always just plug the board in and reconnect the battery and test it with the board hanging out loose.

I have boxes of good test boards for most machines......Makes it real easy to do a quick test and move on if the board is not the issue....

After re-reading your original post I think it very well maybe just the board.....The flight boards work fine ....

thank you for the advice. my board should be here tomorrow so i will tackle this job this weekend. do you think it is a good idea to put a fan inthe compartment and just have air flowing so that it isn't just hot air sitting

The cooler air is drawn in along the front of the machine below the base. If you hold your hand under their when it’s running with the service door on as it always should be you’ll feel the air suction from the internal fan. Move your hand to the right and you feel the hot exhaust air under the muffler inside.

Best thing you can do is make a piece of sheet metal to wall off the hot air from getting to the cool air intake area. Onan makes some air deflectors but simple sheet metal works fine.

The lower to the ground the worse it usually is for a potential problem.

I’ve seen a terrible install that prematurely killed a machine run in the heat of the Miami area.

A digital sign truck. Generator engine was hurt with maybe 1000hrs.

Usually takes 3-4 thousand hrs to get to that point on most machines decently installed

quote:

Originally posted by SCDIV1:
The cooler air is drawn in along the front of the machine below the base. If you hold your hand under their when it’s running with the service door on as it always should be you’ll feel the air suction from the internal fan. Move your hand to the right and you feel the hot exhaust air under the muffler inside.

Best thing you can do is make a piece of sheet metal to wall off the hot air from getting to the cool air intake area. Onan makes some air deflectors but simple sheet metal works fine.

The lower to the ground the worse it usually is for a potential problem.

I’ve seen a terrible install that prematurely killed a machine run in the heat of the Miami area.

A digital sign truck. Generator engine was hurt with maybe 1000hrs.

Usually takes 3-4 thousand hrs to get to that point on most machines decently installed

Lower to the ground is one of the worse problems I’ve seen...

Close to the ground is an Onan Killer

Has nowhere to go but up and right back in the machine.

Engine runs so hot it accelerates the normal cylinder head failures and works on other parts as well.

Control board fails, carbs fail, intake gaskets fail.....

Saw a living quarters trailer a couple years ago brand new and generator was shutting down. At a race and it was pretty hot out...

Generator got so hot the fuel was vapor locking.....Very poor install machine sitting flat on the floor and nowhere for the heat to go.....A major trailer builder too....

Someone had one of those cooling fans used under the hood of racecars and it got them thru the weekend.

They made some changes to fix the issue or at least improve it....

quote:

Originally posted by SCDIV1:
Close to the ground is an Onan Killer

Has nowhere to go but up and right back in the machine.

Engine runs so hot it accelerates the normal cylinder head failures and works on other parts as well.

Control board fails, carbs fail, intake gaskets fail.....

Saw a living quarters trailer a couple years ago brand new and generator was shutting down. At a race and it was pretty hot out...

Generator got so hot the fuel was vapor locking.....Very poor install machine sitting flat on the floor and nowhere for the heat to go.....A major trailer builder too....

Someone had one of those cooling fans used under the hood of racecars and it got them thru the weekend.

They made some changes to fix the issue or at least improve it....

This is most of Goddards problem IMO....same deal living quarters trailer with gen set to low

thanks for help this past weekend Bell. I will do like you were telling me as well to help it out.

Fixed my 5500 with only about 400 hours on it but in a 2006 Super C. At track it just stopped. Attempted to start and could tell it was running or trying to by heat out of the exhaust while cranking but would just stop as soon as start was released.

Pulled the little bushed on the stator and looked in there while cranking it. Could see that it was not turning - hence was not generating it own power to keep it running.

Had to pull the whole unit - honestly was not as bad as people make out to be. With a little help two guys with some floor jacks can easily do it. Got it out and tore it all apart and as suspected the belt that drives it simply dry rotten and broke.

Replaced it along with some other odds and ends for about 100 dollars and its been better than ever. Think before the belt was slipping at times and causing some low power on demand.

Might want to make sure it isnt that before putting in the board. Cant recall the code I was getting but I thought it was the board as well until I noticed it running while cranking and investigated a little more.

The brushes on mine were way back in above the starter on the left of the unit. One 10mm will allow them to be pulled. Mark the wires before taking them off.

Then crank it and be sure the stator is turning... If not it has something to do with the belt that drives it.

There is a rubber coupler bolted to the flywheel.
They break more often than the belts
The belts break more from getting soaked with oil from oil leaks and spills filling it.

I can usually tell the rotor isn't turning just from the different sound it makes cranking and starting....

The control reads output frequency or lets call it RPM.....and also voltage. If the rotor is not turning obviously there is nothing to read

Fault codes are often misleading and Sometimes the fault code is helpful.....Check the basics first.....

The 7KW and the 5.5KW are basically the same machines. Physical size and engines are the same.

The 5.5kw engine runs at a slower rpm and they live longer

The 7kw engine runs faster to get more power and the engines work harder because of that

Proper generator end speed is accomplished by changing the pulley and belt and the generator end itself is different....

The 5.5's are real popular in Motorhomes with 2 AC's

This message has been edited. Last edited by: SCDIV1,

Thanks for the directions on doing the job SCDIV1. I put the new board in yesterday when i got home from work. Probably took 15 from start to finish I can see how you could do it with your eyes closed lol. I let the generator run with almost everything turned on in trailer for a good 2-3 hours with no issues.

He has helped thousands. (No Joke) He is truly an asset for all. (Rich) Wealth of knowledge is priceless.Ever a time i have an issue on all my Miller machines. (5) He would come first before a Miller repair facility.

Thanks....Free advice is easy and I like helping people fix things

I am working right now on a Miller Trailblazer 325 with a Kohler EFI engine and have almost no idea why it's doing what it is doing...and I've wrestled with these machines before.

Lets complicate machines as much as possible is the moto anymore of manufacturers.

It has an EFI engine and lets also add an Inverter power section.....and every one of these I've ever seen the inverter powered outlet does not work.

Only about 1 thousand dollars to fix.....RIGHT !

And I also have a little junkpile Onan 2.8 out of a motorhome and it's granny's and she's 84 and wants to go to Alaska one more time and was trying to go somewhere this weekend.....

How soon can you fix it......Owner already did a lot of work and gave up.....

Sometimes I am a junkpile magnet !! LOL

Yesterday I had to turn a job away and it was a decent sized diesel pusher. Generator needs to come out and I had to bail out of that one....

Owner was in bad shape and really should not be driving this thing.....

I try to watch him as he's backing up and he backs right into a company owned vehicle. Me yelling STOP and holding my hand up.....Nope, he just kept slowly backing up....than blames me for directing him !

Very little damage to the car but his motorhome got the worst of it.....

Not a good day......

Retirement continues to be more and more attractive....I am absolutely certain I could catch a bass if I was at the lake