Honda eu2000i 12v outlet for fan?

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The generator produces unregulated AC which is rectified to DC, this circuit supplies the 12V outlet. It is then inverted to 120 VAC 60Hz. If power is bled off the DC circuit a low voltage signal will go to the inverter producing the wrong output.

This explanation is not correct. The DC output is driven from its own winding on the eu2000i's stator and has no electrical interaction with the windings that drive the 120 volt inverter. The DC output is not only unregulated, it is unfiltered. Here are some DC output measurements from my eu2000i:

With no load, output peaks are 20 volts at low idle (eco on), and 30 volts at high idle (eco off). At low idle both filaments of an 1157 bulb results in an RMS voltage of 9.2, peak voltage of 17, and a load of 1.9 amps. At high idle (recommended for charging) with the same load the RMS voltage is 14.2, peak voltage 27, and the load is 2.45 amps. On a scope, the waveform looks like ~50% duty cycle pulsating DC.

What does this have to do with a fan? I'd guess that a straight DC fan has a chance of doing ok. Most fans used in electronic devices use brushless motors and have internal electronics to create a rotating magnetic field in the stator. I don't have a clue how they'd react to the DC charging output. You could always add your own filter circuit to eliminate any potential problems.

Well, poo,
Checked the voltage with eco off, spiked to 19.5v . Yep cooked my little pc fan , hahahha
So to the parts store to get a 12dc elect fan tomorrow, It should handle that spike way better.

I also found this post on the forum , Guy used his 12v for fan looks like.

If had had initially known I would use th e12v outlet , I would have got a bigger fan ,
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28956619/srt/pa/pging/1/page/1

I will try and get pics of my project , to get some input from you all.

romore wrote:
That is correct. The generator produces unregulated AC which is rectified to DC, this circuit supplies the 12V outlet. It is then inverted to 120 VAC 60Hz. If power is bled off the DC circuit a low voltage signal will go to the inverter producing the wrong output.

The schematic indicates there is a totally separate winding on the transformer for the 12 volts, which then is taken out from the bridge directly to the connector. Other than the thermal load issue if you were loading the A.C. to the maximum, which would defeat the overload protection, there is no interaction between the two circuits. You can use both outputs at once.
I'd be a bit nervous about the voltage, which is significantly higher than 12 volts. When I measured mine it was more like 17 volts. If nothing else add a capacitor for a bit of filtering and accept the fan may not live too long with the high voltage.

Hmm you think bleeding 2 little PC fans at 1.50 amps each would effect it ?

That is correct. The generator produces unregulated AC which is rectified to DC, this circuit supplies the 12V outlet. It is then inverted to 120 VAC 60Hz. If power is bled off the DC circuit a low voltage signal will go to the inverter producing the wrong output.

I don't have a Honda but there is a warning in my owners manual to NOT use the 12 volt and the 120 volt at the same time.

I believe there's lots of noise and ripple on that line.
If their motors don't run hot on it then they should be fine.