WheelHorse520H 708 #1 Posted November 25, 2021 (edited) I have a 1988 520-H that I really enjoy but one thing I don’t like is when all the gauges work except for one or two. The biggest one that bothers me right now it the tach. I know it runs off of the voltage regulator, but I know it’s not that because I just replaced it because the tractor wasn’t charging. The tach either drops (when the key is on but the engine is not running) or it stands straight up, even at idle. Is it just time for a new tach or could it be something else. The voltage gage, the hour clock, the vacuum gage (I don’t think it has wires to it though, just the vacuum line), and the fuel gage (for the most part, it’s not perfectly accurate but it still moves) all work. Ideas? Thanks, Andrew P.S. Happy Thanksgiving Edited November 25, 2021 by WheelHorse520H 1 Share this post Link to post Share on other sites
lynnmor 7,718 #2 Posted November 25, 2021 Be sure that the tach wire, (usually gray) is connected to one of the outboard terminals of the regulator. It piggy backs with one of the stator wires. 2 Share this post Link to post Share on other sites
WheelHorse520H 708 #3 Posted November 25, 2021 10 minutes ago, lynnmor said: Be sure that the tach wire, (usually gray) is connected to one of the outboard terminals of the regulator. It piggy backs with one of the stator wires. On the new regulator the B+ is on the left (looking from the flywheel side) rather than the middle. All connections are clean and solid. The piggyback is connected. I am not sure what else besides a bad tach would cause it to go all the way up or all the way down. Andrew Share this post Link to post Share on other sites
lynnmor 7,718 #4 Posted November 25, 2021 1 hour ago, WheelHorse520H said: On the new regulator the B+ is on the left (looking from the flywheel side) rather than the middle. All connections are clean and solid. The piggyback is connected. I am not sure what else besides a bad tach would cause it to go all the way up or all the way down. Andrew I suspect you have the wrong regulator. Measure the AC voltage across the two terminals not marked with a B, it should be as stated in the Onan Service Manual. Then measure the DC voltage with the engine running, it should be about 14.4 volts. Share this post Link to post Share on other sites
WheelHorse520H 708 #5 Posted November 25, 2021 11 minutes ago, lynnmor said: I suspect you have the wrong regulator. I bought it from onanparts.com and they only have one listed and it says it fits the P220G. I’ll test it tomorrow. Now that I think about it the voltmeter was only reading just over 12 bolts, maybe it’s the stator. Anyway I’ll do the test tomorrow and see what’s up. Thanks. Share this post Link to post Share on other sites
Handy Don 13,683 #6 Posted November 26, 2021 @WheelHorse520H When I last installed a new regulator, I noticed that one of the outside connections was actually bridged electrically with the center connector. If yours is like that, and you connected the tachometer to the "joined". connector, it might not see the changing voltage it needs to work. I'd try an experiment and swap the connections to the two "outside" terminals of the regulator. It won't make any difference to charging the battery or using other accessories, but it might give you back the tach. Share this post Link to post Share on other sites
WheelHorse520H 708 #7 Posted December 1, 2021 (edited) On 11/25/2021 at 12:39 PM, lynnmor said: I suspect you have the wrong regulator. Measure the AC voltage across the two terminals not marked with a B, it should be as stated in the Onan Service Manual. Then measure the DC voltage with the engine running, it should be about 14.4 volts. The AC voltage was about 5 volts higher than the spec but I am not sure that the engine RPM were where they should be because the tach (as you know) doesn’t work. The DC voltage was within the spec of the manual. The resistance of the stator was 0.3 ohms but the spec is up to 0.1 ohms. Is this a cause for concern even thought it seems to be charging well? Edited December 1, 2021 by WheelHorse520H Share this post Link to post Share on other sites
lynnmor 7,718 #8 Posted December 1, 2021 4 minutes ago, WheelHorse520H said: The AC voltage was about 5 bolts higher than the spec but I am not sure that the engine RPM were where they should be because the tach (as you know) doesn’t work. The DC voltage was within the spec of the manual. The resistance of the stator was 0.3 ohms but the spec is up to 0.1 ohms. Is this a cause for concern even thought it seems to be charging well? Meters often are less than perfect at those low readings, I think that your system is working correctly and the tach is faulty. 1 Share this post Link to post Share on other sites
WheelHorse520H 708 #9 Posted December 1, 2021 (edited) 12 minutes ago, lynnmor said: tach Do you know where I could get one for a 1988? Any vendors here that have them? Edited December 1, 2021 by WheelHorse520H Share this post Link to post Share on other sites
lynnmor 7,718 #10 Posted December 1, 2021 8 minutes ago, WheelHorse520H said: Do you know where I could get one for a 1988? Any vendors here that have them? Sent you a PM. Share this post Link to post Share on other sites
WheelHorse520H 708 #11 Posted December 1, 2021 Just now, lynnmor said: Sent you a PM. Got it thanks. Share this post Link to post Share on other sites
