Cooling air deflector for Onan generator

[deputydog]

I've been having issues with my Onan Marquis 7000 gas generator and after having the shop replace the coils and stator and still having the same Code 47 come up (lost ignition) one thought the shop had was that they have seen some Onan's basically suck the hot cooling air right back into the cooling intake and heat up. Since my stator was badly discolored after only 400 hours that might just be part of my units issue so I decided to add a deflector send the heated cooling air away from the cooling intake.

Basically on the underneath right hand side of the generator (if you are looking at the front cover) there is a hole about 6 inches by 18 inches that serves as the exhaust port for the cooling air that cools the internal parts of the generator (no engine exhaust comes out of this port though the muffler and exhaust pipe exit through it). On the underneath left side of the generator is the intake port for the cooling air as well as the carburetor air intake.

As shown in the attached photos I just fashioned a metal panel that blocks the hot air from the exhaust port from directly entering the intake and deflects it away from the cooling intake. I made it out of some aluminum diamond plate that I had and some aircraft silicone baffle seal to seal the top.

The temperature reduction inside the generator is significant so maybe it will fix my code 47 issue. No doubt all the internal components will last longer.

[94-Newmar]

I'll assume yours is an HGJAB model.

In all my years I've never seen a heat issue such as you describe, especially with an open bottom mounting, such as in your coach. Your deflector certainly will not hurt anything but I do not believe it's going to help anything either. You mention the stator was discolored; is it turning blue? Is it only discolored on the side exposed closest to the drafting intake? Only discolored near the top where the rotor bearing is? It would take a tremendous amount of heat to discolor it - much more than what the exhaust could produce.

Do you have any other troubleshooting info from the work order they may have written?

I would have only replaced the stator if any of the windings resistance measurements were incorrect or shorted to ground (which is most common). However, the problem, as you describe, still exists. I wonder what their findings were on those values? I would look more towards a short in the "kill wire" leads which are also part of the same harness going into the P1 connector and a close look at the drive belt and tensioner.

Unfortunately, these units can only store 1 error code and the only one you can retrieve is the last one that occured - and in many cases, there would be another error that happened first, got stored, then another error quickly occurred as a result of the first and overwrote the original error. The only way to be sure is to run the unit on a breakout box, which allows the unit to stay running regardless of the error - it also allows you to see the error as it occurs in realtime.

Please keep us posted.

[deputydog]

94-Newmar:

Thanks for the reply.

The stator was still functional but the coating on the wires was black except for in one small spot which was the amber brown lacquer color that you see on most starters/generators etc. Some of the tie-down strings used to hold the windings in place prior to coating had come out of the coating. It was my call to replace it since it was a $300 part and the unit was already disassembled and out of the coach which is most of the cost. I didn't want to do this twice.

Both coils were replaced and the leads going to the P1 connectors are part of those coils up to the butt connectors that connect them to the P1 leads. The mechanic also said he checked all of the leads and P1 pins.

From what I have read, it could also be the controller board and I asked the mechanic about that and he said he changed it out when in the shop the first time and it still had the same code 47 so he reinstalled mine.

The belt tensioner was replaced as the bearing was a bit stiff. Belt was fine.

I have heard of the breakout box but did not specifically ask if they had one, but assumed since they were a Onan Power South shop that they would have one. I never saw it hooked to anything line that - just a recording multimeter which he was checking frequency and voltage with since their engineer said sometimes being low frequency would cause erroneous codes.

With regard to the deflector, I can tell you that there is a SIGNIFICANT difference in the cooling air entering the unit now compared to before it was installed. You could not keep your arm under the cooling side near the exhaust side for more than a few seconds before it was uncomfortable and now you can leave it there and it's near ambient temperature so it's a big improvement - maybe not the solution to the original problem. The change in temperature will also increase the engine output due to the increase in density of the intake air. Might help some in the mountains if we ever get there.

Headed to an airshow next week so it will get some more time on it and see what happens. Taking my Honda with me just in case.

My wife's theory is that it just needed time to adjust to the new parts!

[deputydog]

We went to the Sun-N-Fun airshow in Lakeland Florida this past week so we got a chance to give the generator another whirl since last time I took it to the Onan shop it did not malfunction.

Leave it to Murphy's law - go on a trip and it wouldn't run for more than an hour before shutting down with code 47. I tried it probably 6 or 8 times during the week and always the same. Runs for a bit and then shuts down. EXTREMELY hard to start after shut down. I got video of multiple shutdowns so they won't think I am crazy at the Onan shop. On the way home we stopped at Cracker Barrel and just for grins I cranked it up and turned on the A/C. Amazingly it was still running when we got done, but that was only about an hour.

Fortunately I took my Honda 7000is and my 2000is so we had all the power we needed and even hooked up the 7000 to a neighbor who's batteries went completely dead and couldn't start his generator.

Off to the shop next week (trip #3) - getting tired of this mess.