dr363305 50 #1 Posted October 22, 2022 Hello and good day. I have 1988 520H that is new to me. When I purchased it, the wires for the charging circuit were not connected and the gauges didn’t function. I wired it up per the wiring diagram and everything was good for a bit. Recently, the 30A fuse has been popping. There are no faults to ground that I have found. I put a voltmeter across the fuse holder and got 13.94V at idle and 15.6V at full throttle. Could the voltage regulator be causing this issue? Or am I completely wrong? Any assistance is appreciated! Feel free to flame me as well for being inexperienced with the Onan platform as well. Share this post Link to post Share on other sites
Snoopy11 5,713 #2 Posted October 22, 2022 8 minutes ago, dr363305 said: 15.6V at full throttle 15.6 is considerably more than it should be. I would say that you need a new regulator... but more testing may be required. I am no electrical expert, so take what I say with a grain... @Jeff-C175... Don 1 Share this post Link to post Share on other sites
Snoopy11 5,713 #3 Posted October 22, 2022 15 minutes ago, dr363305 said: 15.6V at full throttle One other suggestion... run a ground wire from battery negative to regulator bolt or metal body of regulator and see if that makes a difference in charging values. Don 3 Share this post Link to post Share on other sites
dr363305 50 #4 Posted October 22, 2022 Now that I think about it, I should be testing across the battery for charging voltage. I am not sure if measuring across that fuse means anything. 1 Share this post Link to post Share on other sites
Snoopy11 5,713 #5 Posted October 22, 2022 (edited) 7 minutes ago, dr363305 said: I should be testing across the battery for charging voltage Honestly, I'm not sure that it should matter. When I have bench tested my engines, I test voltage output directly from the charging output terminal on the regulator with no positive battery connected (only using negative on battery to ground the engine). I've never had one that was grounded correctly go above 14.6... Again... I disclaim... I am not an electrical guru!!! EDIT: I'm interested to hear what more educated electrical minds have to say about this... but I don't believe that it is the battery's job to regulate voltage! Don Edited October 22, 2022 by Snoopy11 1 Share this post Link to post Share on other sites
Ed Kennell 35,836 #6 Posted October 22, 2022 Make sure the regulator is grounded. Loosen and retightening the mounting screw may solve the problem. 1 Share this post Link to post Share on other sites
Jeff-C175 7,195 #7 Posted October 22, 2022 Yes, measure across the battery and not across the fuse. If you are measuring 15.6 at the battery, either the battery is 'soft' or the regulator is severely over charging the battery. 1 Share this post Link to post Share on other sites
dr363305 50 #8 Posted October 22, 2022 (edited) 4 minutes ago, Ed Kennell said: Make sure the regulator is grounded. Loosen and retightening the mounting screw may solve the problem. When I was initially reconnecting everything, i cleaned the area where it bolted to the blower shroud with a brass wire wheel. I will check continuity to ground and run a separate ground wire to see if the issue goes away. 10 minutes ago, Snoopy11 said: ... but I don't believe that it is the battery's job to regulate voltage! Correct, but the charging voltage will still show up across the terminals if the engine is running and charging. Edited October 22, 2022 by dr363305 Spelling 1 Share this post Link to post Share on other sites
Ed Kennell 35,836 #9 Posted October 22, 2022 Check the condition of the 30A fuse holder. I have found them partially corroded away. 3 1 Share this post Link to post Share on other sites
8ntruck 6,379 #10 Posted October 22, 2022 Does that tractor have an amp meter or a volt meter? Amp meters can cause fuses to blow when they go bad. If your tractor has an amp meter, you can disconnect the wires on it and directly connect them together, taking the meter out of the circuit as a test. 1 1 Share this post Link to post Share on other sites
Evguy 550 #11 Posted October 22, 2022 I have seen that with bad regulator, putting out too much, battery won’t take the current and fuse opens. I always thought charging circuit should be fused lower and separate from main fuse. 2 Share this post Link to post Share on other sites
dr363305 50 #12 Posted October 22, 2022 4 hours ago, 8ntruck said: Does that tractor have an amp meter or a volt meter? Amp meters can cause fuses to blow when they go bad. If your tractor has an amp meter, you can disconnect the wires on it and directly connect them together, taking the meter out of the circuit as a test. No amp meter. It has a battery voltage meter. And while cutting grass earlier, it was showing 14V. I had a party to prepare for earlier today, so tomorrow I will put my multimeter on it and see what it does. Share this post Link to post Share on other sites
Snoopy11 5,713 #13 Posted October 22, 2022 4 minutes ago, dr363305 said: while cutting grass earlier, it was showing 14V. Did you do anything different for it to show 14V instead of 15+ ? Don Share this post Link to post Share on other sites
dr363305 50 #14 Posted October 22, 2022 1 minute ago, Snoopy11 said: Did you do anything different for it to show 14V instead of 15+ ? Don 15.6V was measured across the fuse. I do not think that reading matters. I need to check across the battery terminals for a more accurate reading. 1 Share this post Link to post Share on other sites
953 nut 51,770 #15 Posted October 23, 2022 35 minutes ago, dr363305 said: 15.6V was measured across the fuse. I do not think that reading matters. I need to check across the battery terminals for a more accurate reading. Measuring across the open fuse holder shows the NO-LOAD potential output of the charging system. The battery is a load and will indeed regulate the voltage seen when the fuse is in place. The fuse blowing randomly is probably telling you that the fuse holder is bad like @Ed Kennell said earlier. Your fuse holder is near the battery and over the years it has been exposed to battery acid fumes, not a good thing. The resulting corrosion acts like a resistor and heats up the fuse. @Save Old Iron gave us an explanation several years ago; f you have a 10 amp current flowing across a 1 ohm resistance (contact corrosion) the electronics formula to calculate power = current squared times resistance so 10 amps x 10amps x 1 ohm resistance = 100 watts !! 100 watts of connector heating is the same as laying a 100 watt soldering iron on the connector. 2 Share this post Link to post Share on other sites
8ntruck 6,379 #16 Posted October 23, 2022 4 hours ago, dr363305 said: No amp meter. It has a battery voltage meter. And while cutting grass earlier, it was showing 14V. I had a party to prepare for earlier today, so tomorrow I will put my multimeter on it and see what it does. DO NOT CONNECT THE LEADS TO THE VOLT METER TOGETER! The magic smoke will escape, then things won't work anymore! 2 Share this post Link to post Share on other sites
dr363305 50 #17 Posted October 23, 2022 14 hours ago, 953 nut said: Your fuse holder is near the battery and over the years it has been exposed to battery acid fumes, not a good thing. This fuse holder is at the front of the engine by the starter solenoid. This isnt the fuse holders by the battery. Not debating if it is bad or not, just that the location is different. 10 hours ago, 8ntruck said: DO NOT CONNECT THE LEADS TO THE VOLT METER TOGETER! The magic smoke will escape, then things won't work anymore! Why would measuring voltage across the battery let out the magic smoke? Im not messing with any wiring on the voltmeter. Share this post Link to post Share on other sites
lynnmor 6,796 #18 Posted October 23, 2022 5 minutes ago, dr363305 said: Why would measuring voltage across the battery let out the magic smoke? Im not messing with any wiring on the voltmeter. No problem checking with a voltmeter. The comment was intended for those that might bypass an ammeter which is OK, but a voltmeter bypass is a dead short. 4 Share this post Link to post Share on other sites
Ed Kennell 35,836 #19 Posted October 23, 2022 1 hour ago, dr363305 said: This fuse holder is at the front of the engine by the starter solenoid. Yes, this is the one that I have often found badly corroded. I replace them with a waterproof holder. 2 Share this post Link to post Share on other sites
8ntruck 6,379 #20 Posted October 23, 2022 2 hours ago, lynnmor said: No problem checking with a voltmeter. The comment was intended for those that might bypass an ammeter which is OK, but a voltmeter bypass is a dead short. Sorry, I did not explain well. On an amp meter, one lead goes to the power supply, the other lead goes to the load. If you disconnect the amp meter, by re moving one lead, you also disconnect power from the load. So, to test to see if the meter is causing a short, it can be removed from the circuit by disconnecting both leads from the meter and commenting them to each other. On a DC volt meter, one lead goes to the positive power supply and the other lead goes to ground. To take a volt meter out of the circuit for testing, just remove the positive lead. As @lynnmor states, removing both leads from a volt meter and connecting them creates a short circuit. 1 Share this post Link to post Share on other sites
Snoopy11 5,713 #21 Posted October 23, 2022 16 hours ago, 953 nut said: NO-LOAD potential output of the charging system. The battery is a load and will indeed regulate the voltage Interesting. Not to hack this thread, but I'd love to hear an explanation of why my bench engine with brand new stator and regulator puts out no more than 14.6 volts with no battery connected... It puts out proper voltage when connected to a good battery as well... Don 1 Share this post Link to post Share on other sites
dr363305 50 #22 Posted October 23, 2022 Update: Measured across the battery terminals and got 13.9V - 14.2V when running. Popped another fuse. I will replace the fuse holder and report back. Thank you all for the help! 1 Share this post Link to post Share on other sites
953 nut 51,770 #23 Posted October 23, 2022 6 hours ago, Snoopy11 said: 14.6 volts with no battery connected... It puts out proper voltage when connected to a good battery as well. Are you saying the regulator connected to the battery is reading the same as without a battery connected? Share this post Link to post Share on other sites
Snoopy11 5,713 #24 Posted October 24, 2022 (edited) 2 hours ago, 953 nut said: Are you saying the regulator connected to the battery is reading the same as without a battery connected? No sir, no sir... I don't think my query came across correctly. I apologize. The engine puts out 14.6 volts with no battery connected at 3,600 RPM. When I put a fully charged battery on it... the voltage fluctuates from 13.5 volts to 14.3 at 3,600 RPM... I tested it again today, and the above are the results. My point in my post was that my voltage on my bench/crate engine NEVER goes above 14.6 volts with or without a battery connected. That is really the basis of my question... what is the voltage range at regulator output terminal? What should we be looking for? EDIT: keep in mind... my electrical knowledge is --slim at most... Don Edited October 24, 2022 by Snoopy11 Share this post Link to post Share on other sites
Evguy 550 #25 Posted October 24, 2022 The regulator needs about 5 volts on b to even work. I read something on my 314 to not run without a battery or damage to electrical system could result, not sure what they are referring to Share this post Link to post Share on other sites
