cleat 4,984 #26 Posted July 17, 2016 If you wire it like that, the tach will see a steady 12 volts and will always read 0 RPM. That schematic is drawn wrong. Tach needs an AC signal to function and will get it from one of the outer AC terminals on the regulators. Only one of the terminals will actually work because the other outer terminal is actually connected to B+ internally. I have attached the 520 wire diagram. Later model 520 wire diagram.pdf Not trying to be annoying, but electronics and electricity is my specialty. I guess that is why I love my 520's. First thing I do when I get one is pull out the wire harness and completely rebuild it. Share this post Link to post Share on other sites
Kurt-NEPA 755 #27 Posted July 17, 2016 You are right Cleat. That can't work. Sorry for bad diagram. Share this post Link to post Share on other sites
Kurt-NEPA 755 #28 Posted July 17, 2016 Here is a picture of my 95 520H regulator and wires. Note the gray wire going to one of the AC connections Corrected Wiring Diagram 2 Share this post Link to post Share on other sites
Bigfish 146 #29 Posted July 17, 2016 (edited) So mine is wired wrong then. The red wire is on the terminal furthest from the battery and the two black wires are on the two terminals closest to the battery. So should move the red wire to the center and hook the grey wire to the terminal closest to the battery? I dont want to fry anything.. Edited July 17, 2016 by Bigfish Share this post Link to post Share on other sites
cleat 4,984 #30 Posted July 17, 2016 Make it like Kurt's. That is how all of mine are wired and they work perfectly. 1 Share this post Link to post Share on other sites
Bigfish 146 #31 Posted July 17, 2016 The tach is now working. Thanks for the help everyone. Much appreciated. 1 Share this post Link to post Share on other sites
Bigfish 146 #32 Posted July 17, 2016 (edited) This one is going to be a long one. The next odd thing I found while tracing wires was this broken sensor on the front cylinder (oil or cylinder temp?). Im almost half tempted to forget I saw it considering how everyone says onan parts are nuts expensive. I also found somesome cut wires on the wiring harnes connector. The last thing for today is paint. The paint on it is all intact no rust, gouges or bubbles There are some skuffs from branches and bushes on the hood. I was wondering if the paint is a triditional liquid coating or powder coat? Also for the black paint on the motor and frontend. Is that a satin black? I want to buff the skuffs out, repaint the black on the front and engine and apply new stickers. Shes the new wagon hauler for the wife so I want it to look good for her. I have a heart attack when she uses one of the 60's or 70's . Just watching her going along at full speed in my charger then slaming into reverse gets me sounding like my grandfather. Lol Edited July 17, 2016 by Bigfish Share this post Link to post Share on other sites
Bigfish 146 #33 Posted July 20, 2016 I tracked down the hi-temp sensor locally. $57 for a temp sensor. Crazy. The guy told me out of the 11 or so authorized cummins power generation service centers in my area that was the last one in the system. Share this post Link to post Share on other sites
