General QuitPact 75D 12 VAC output

[KevinWLeach]

Have a Generac QuitPact 75D Serial Number 3820647 that is only making 12 VAC between L1 or L2 and Neutral with 62 Hertz. Connected wire 4 to 12 VDC, measured 49 VAC between wire 2 and wire 6 and measured 28 VAC between 11 and 22. With wires 11, 22, and 6 reconnected to VR, measured DC Amps between 12 VDC and wire 4 to be 0.58 Amps. Checked Excitation CB and confirmed continuity. Stator Excitation Winding resistance was measured to be 1.20 ohms. AC Power Winding resistance was measured to be 0.14 ohms between wire 11 and wire 22 and 0.17 ohms between wire 33 and wire 44. Resistance was checked on the sensing legs wire 11 and 22 which was 0.19 ohms. Any ideas why the generator is only making 12 volts AC between L1 or L2 or neutral?

[Chris]

It's odd that with 12V on the rotor and the unit running, you're only getting 28VAC...

What is your rotor resistance (between 0 and 4 wires with them removed from the AVR)?

[KevinWLeach]

Chris thanks for the reply. I rechecked all of my measurements and realized I made two mistakes when I made the original measurements. I missed that both wires attached to the AVR F+ terminal were to have +12volts applied. Also, I failed to realize that a load was still on the generator. I removed wires 11a and 44a from the terminal block and shielded the terminals to prevent an arc from occurring. The voltage measurements after correcting my errors are 95 VAC between wires 2 and 6, 86 VAC between 11a and 22, and 85 VAC on sensing 11 and sensing 22. I did check the resistance between wire 0 and wire 4 to be 30 ohms. One question though, I got three different readings across wire 0 and wire 4. Each reading was taken after bump rolling the motor/generator with the start button. Is that normal? Resistance ranged from 25 ohms to 85 ohms.

[Chris]

25 ohms is more normal for sure. You may want to inspect the slip rings if that's possible!

It sounds like if you have all of those readings that it's either an AVR problem, or a field boost problem. With everything connected as normal, if you bump the 4 wire with 12V, will the unit produce normal voltage on its own?

DO NOT leave 12V connected there for more than a second or so. Doing so could result in damage to the unit!

[KevinWLeach]

Thanks again Chris. I bumped 12 volts to wire 4 with everything connected normally. L1 to Neutral still measured 30 VAC after bumping the 12 volts.

As far as the slip ring inspection, there is not enough room around the generator to remove the cover to get access. Should I tell the owner that the generator needs removed from its current installed location to inspect the slip rings? The generator is mounted under a Semi-truck RV.

[Chris]

It may be worth it to try a new AVR before you tear it all apart...

If you bumped with 12V and the AVR didn't take over, that's most likely the issue, as long as the slip ring resistance it's getting way out of hand during those tests. I assume that you can access the AVR without removing the unit?

That serial number doesn't come up for me (and it's not old enough to not be in there), so not sure if there's a typo there or not? It's probably this AVR, but wanted to check: https://shop.gentekpower.com/products/g ... ulator-avr

[KevinWLeach]

I do have access to the AVR. I attached a picture of the serial number plate.

[KevinWLeach]

Will the AVR with cooling fins fit behind the cover plate? The AVR that is currently installed does not have the cooling fins.

[Chris]

The fins add about 3/8" to the overall depth of the unit (and you'd need longer screws). The non-finned version can be seen here if that other one can't be made to work: https://shop.gentekpower.com/products/g ... vr-no-fins