Generac 7550exl High Voltage

Paul062

New member
model 01470 rev.1 serial# 1010844232 15 hp briggs engine. 83970 rev U board. getting 160 volts out of both 120v plugs. 320 volts on 220 plug. would this be the voltage regulator? checked 10 pages of generac issues didn't find any help. Thanks Paul
 

Motorhead

Subscriber
Re: Generac 7550exl high voltage

Have you checked engine RPM or the generator HERTZ? If the set has a voltage regulator board, MARK the positions of the pots on the board and with the generator shut down, work the pots back and forth several times and RETURN them to the marks you made before moving them. This can clean any bad connections.
 

Paul062

New member
Re: Generac 7550exl high voltage

how would I do this? I don't have any tools in tool box to check that.
 

Paul062

New member
Re: Generac 7550exl high voltage

Was able to get voltage and hertz readings 149v 56.7 hertz by slowing the engine speed down to 130v 51. hertz. have not been able to check engine rpm yet.
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

AVR is almost certainly dead, there is an adjustment on it you can try, but if you are certain no one messed with it, replace the AVR.

Dunno what meter you checked hz with, try checking utility, it should be 60hz, if it's accurate, crank the speed up on the gen till you get about 61-62 hz. no load.
 

Paul062

New member
Re: Generac 7550exl high voltage

not sure what avr is but the trim pot on pc board does nothing doesn't change voltage or hertz.
 

Paul062

New member
Re: Generac 7550exl high voltage

ok think I figured out what avr is analog voltage regulator right? ok where is this located and where can I get a replacement.
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

I think your gen will have a mechanical governor for the speed. There is usually a tension spring holding the throttle open, and it should have a screw or something to adjust the tension, increasing the tension adjustment will increase the speed. no load target should be 61-62 hz. The volts will go up more, but you still need the voltage regulator to fix that issue.
 

Paul062

New member
Re: Generac 7550exl high voltage

found a avr on amazon #84132GS mine is G84132 0415. would it be the same with updated part # ?
 

Bassplayer1985

Subscriber
Re: Generac 7550exl high voltage

Dont buy an 84132gs, its not the problem. Get your speed back to 62.5hz or 3750rpms. If the trim pot does nothing then the 83970gs board needs work, or possible bad connector on the white snubber cable between it and the 84132GS.

The worst thing one can do is reduce speed to get the correct voltage. Yes voltage is in range doing that, but the slower speed can overheat/overload electric motors specifically.
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

His speed is too LOW, and his voltage too high. When he speeds up, it can only increase voltage output. 2 problems. Probably been living with the low speed for a while tho.
 

Paul062

New member
Re: Generac 7550exl high voltage

Thanks for the help fellows.. Will double check the white snubber wire. If I need a new board 83970 Rev. U board where would I get it?
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

It's made and tuned for 60hz nominal. Running it too low is hard on the generator, and hard on whatever you are powering.

RPM and Hz are two ways to measure the same thing on your set, no need to waste money on a tach if you have a frequency meter, and vice-versa.
 

Paul062

New member
Re: Generac 7550exl high voltage

Turning up the rpm to achieve the correct Hz is way over speeding the engine. Really don't want to compound my issue.
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

Not trying to argue....but no, it's not.

3600 RPM makes 60hz. Period. The mechanical governor 'droops' with load, in other words, the RPM drops as load is increased, so they compensate slightly by setting the speed a bit higher, 61-62 hz, which will be 3660-3720 RPM, no load. Fully loaded, the set will drop to perhaps 58-59 hz, 3480 to 3540 hz, or so.

I did ask for you to check the calibration of your hz meter, by testing the utility electricity. They are always 60hz and basically never off of that by more then 0.1 hz, so 59.9-60.1 hz.

Slower speed engines certainly are quieter and less rough on the ears. I think you got used to the set running around 3400 hz, loaded will go even lower, but it's not right.

The only way for the engine/hz relationship to be off is if the armature is slipping on the crankshaft. That does enough damage fast enough, that it would be it's own issue by now.
 

Paul062

New member
Re: Generac 7550exl high voltage

Thank you for your patience! ok House current is 118.5 volts at 59.95 hertz. Meter being used is a Radio Shack 22-172 a/c d/c tru rms clamp on meter with probes. The original issue was high voltage low hertz. on generator. 149 volts 56.7 hertz. Since then I have slowed engine speed and raised engine speed. So I think until I know for sure the engine rpm and check voltage and hertz I'll let you know. Kinda like starting all over, but at least we'll have real numbers to start with. Again thanks for helping me sort this out!!!
 

Paul062

New member
Re: Generac 7550exl high voltage

Ok hooked up tach, brought engine upto 3750 rpm. measured 162.6 volts with the hertz bouncing from 62 to 78. Hertz will not stop bouncing, volts stayed steady. Tried it at 3600 rpm. Volts 153.8 and steady, hertz bounced from 60 to 80 or higher. Again no steady reading. Meter on house power was 118.5 volts and 59.95 hertz. Any more things I can try? Thanks again for your input. The trimmer pot on the control board did nothing up or down.
 

pegasuspinto

Active member
Re: Generac 7550exl high voltage

Is the generator speed hunting/surging, etc? Meters sometimes pick up harmonics or noise and causes errant frequency readings. If you were REALLY going from 60 to near 80 hz I think you'd of mentioned that however, that would be pretty dramatic, the gen would just about be jumping around and having people head for cover.

You still have/had two issues. The regulator is still bad, IMHO.

Leave the speed at 3750 or so.

A small load can stabilize the frequency reading sometimes, but right now most things you plug into the generator would get smoked at the 153 volts.
 
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