# Honda 3500sx high voltage issue



## shootis (Oct 20, 2015)

I have a Honda 3500Sx that starts and runs great.

The 120 volt output is spot on when the 120/240 switch is in the 120 position, I checked the Hertz and its 60 Hz

My issue is when the switch is in the 240 position, the voltage meter is pegged and when I measure the output the 120 outlet is now around 177 and the 240 outlet is 350 volts or so.

Any thoughts on this one, I'm confused. I swapped in another AVR and got the same results.

Thanks!


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## Osviur (Sep 7, 2015)

*High voltage*

Hi Shootis,

I think that your problem resides in the 120/240 SW: The output voltage in a determined generator depends of two main parameters, the RPM and the intensity of the exciter field.

RPM are fixed by a centrifugal control (governor)or an electronic one, and in a AC generator (w/o inverter), driven by an engine, are maintained in 3600 RPM or 60 RPS in a high speed gen or 1800 RPM or 30 RPS, in a low speed one, to obtain 60 cycles per second or 60 Hertz. 

The exciter magnetic field is created by a current in the rotor windings. In this case via two slip rings that transmit current sent by the AVR (automatic Voltage Regulator). The AVR is fed with power comming from the exciter winding (AC), rectified by a diode bridge, smothed with a capacitor and regulated in its way to the rotor by an electronic circuit that compares a reference voltage (a fixed voltage), to say 5 volts, with a proportional fraction of the output voltage and generates an "error signal" that increases or decreases the AVR current to the rotor windings. Commonly this is a ON-OFF process.

Returning to your case, if the AVR controls OK the 120 V output, the AVR is OK. But when you switch to the 120/240 position, I think, that the feedback signal (that fraction of the output voltage) is lost for a contact failure in the switch, contacts 10 (Bu), 11 (Lg) and 12 (W). This absent voltage generates an error signal increasing the output voltage of the AVR, but there is not an increase in the feedback, so the AVR puts all the voltage available to obtain a response, lost in the switch, and the generator overexcited, generates the maximun voltage that is capable, to say 370 volts or so.

Try first, with the engine stopped, moving the 120-120/240 switch several times from one position to the other, may be this gen has been used only in the 120 position. If this does not solve the issue, check the mentioned contacts: 11 is the common (Lg light green?) going to the AV with the feedback signal to be compared with the reference , 10 is the failing contact (Bu) and 12 is the 120V position (white).

Have a nice day


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## shootis (Oct 20, 2015)

*It's fixed thanks to Osviur*

Hi,

I just wanted to follow up on this repair. Osviur had me look at the switch which checked out fine but it did get me going in the right direction.

Thanks to his explanation of how it should work, I looked at the unit a few more times and finally found a bad connection on the feedback connection for 240.

The blue wire had a funky connection where it entered the 6 pin connector.

Thanks again for your help!


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## Osviur (Sep 7, 2015)

*Ovevoltage*

You are welcome Shootis.


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