Wayne0 741 #1 Posted Friday at 09:49 PM (edited) My 520H Onan 20 doesn't seem to be charging. 12VDC at battery with a DMM on full throttle. New regulator and separate ground to battery. 9 pin maybe? Edited Friday at 09:50 PM by Wayne0 Share this post Link to post Share on other sites
ri702bill 8,769 #2 Posted Friday at 10:14 PM 23 minutes ago, Wayne0 said: 9 pin maybe? Most likely. Check for melted / toasted terminals & wires... 1 Share this post Link to post Share on other sites
squonk 41,963 #3 Posted Friday at 10:28 PM 9 pin and check voltage regulator and it's ground (mounting surface) 1 Share this post Link to post Share on other sites
Wayne0 741 #4 Posted Friday at 11:58 PM Reg is new with an independent ground to bat neg. Gonna check 9 pin and maybe eliminate it. I suppose the new reg could be bad? Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,187 #5 Posted Saturday at 01:42 AM With the key in the run position but the engine not running see if you have battery voltage at the regulator DC+ terminal. You should have. If not the charge current can't get to the battery. 2 Share this post Link to post Share on other sites
WHX?? 49,953 #6 Posted Saturday at 02:09 AM (edited) Check the fuse too. We have seen the blades melted right off. 12 hours ago, Wayne0 said: 9 pin and maybe eliminate it. All mine have charge pin taken out of the 9. Edited Saturday at 12:27 PM by WHX?? speeling 1 Share this post Link to post Share on other sites
953 nut 56,814 #7 Posted Saturday at 12:26 PM 12 hours ago, Wayne0 said: Gonna check 9 pin and maybe eliminate it. 10 hours ago, WHX?? said: Check the fuse too. We have seen the blades meted right off. Both of these are good thoughts Not all 520s are wired the same, give us the Model number and it can be narrowed down. Share this post Link to post Share on other sites
WHX?? 49,953 #8 Posted Saturday at 12:29 PM 12 hours ago, Wayne0 said: suppose the new reg could be bad? Not impossible ... especially the cheapys in the jungle. Share this post Link to post Share on other sites
Pullstart 63,604 #9 Posted Saturday at 03:24 PM All I know if seeing the thread title has gotten me twice now. Like a free tractor! 7 Share this post Link to post Share on other sites
Wayne0 741 #10 Posted Saturday at 05:02 PM (edited) 15 hours ago, gwest_ca said: With the key in the run position but the engine not running see if you have battery voltage at the regulator DC+ terminal. You should have. If not the charge current can't get to the battery. Key on or off, I get battery voltage at all three terminals. ??? (plugged in) However, with the wires unplugged from the reg, I get no voltage at the 2 out side wires and bat on the ctr. Sound like a bad reg? Edited Saturday at 05:24 PM by Wayne0 Share this post Link to post Share on other sites
Wayne0 741 #11 Posted Saturday at 05:10 PM 4 hours ago, 953 nut said: Not all 520s are wired the same, give us the Model number and it can be narrowed down. 1 Share this post Link to post Share on other sites
lynnmor 7,495 #12 Posted Saturday at 05:30 PM Download the Onan Service Manual, go to page 8-5. Now you will know if there is a problem on the engine side of things. Share this post Link to post Share on other sites
Wayne0 741 #13 Posted Saturday at 05:57 PM 24 minutes ago, lynnmor said: Download the Onan Service Manual, go to page 8-5. Now you will know if there is a problem on the engine side of things. OK, AC voltage is within spec. Still only battery voltage at DC output terminal. Gotta be a bad regulator. Share this post Link to post Share on other sites
Handy Don 13,109 #14 Posted Saturday at 06:32 PM 31 minutes ago, Wayne0 said: OK, AC voltage is within spec. Still only battery voltage at DC output terminal. Gotta be a bad regulator. A couple of years ago I had one fail when the “potting” material separated from the metal housing and allowed moisture into the guts. @lynnmor's encouragement kept me from getting super frustrated! 😁 1 Share this post Link to post Share on other sites
953 nut 56,814 #15 Posted Sunday at 01:22 AM Thanks for posting the model number. The white B+ wire from your voltage regulator goes through the 9 Pin connector to the 25 Amp Fuse then back through the 9 Pin on the Red wire on its way to recharge the battery. A bad fuse holder, fuse, 9 Pin or regulator connector could cause the lack of charging. Share this post Link to post Share on other sites
Wayne0 741 #16 Posted Sunday at 12:38 PM @953 nut Thanks for that. I believe I solved the problem. Have AC in to the reg, but no DC out. 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,187 #17 Posted Sunday at 01:40 PM On 2/21/2025 at 8:42 PM, gwest_ca said: With the key in the RUN position but the engine not running see if you have battery voltage at the regulator DC+ terminal. You should have. If not the charge current can't get to the battery. The reason this is important is the battery needs to turn the regulator on so to speak before it can regulate the regulator DC+ output. That is why it is important to have the regulator DC+ terminal powered by the battery. 3 Share this post Link to post Share on other sites
Wayne0 741 #18 Posted Sunday at 06:53 PM 5 hours ago, gwest_ca said: The reason this is important is the battery needs to turn the regulator on so to speak before it can regulate the regulator DC+ output. That is why it is important to have the regulator DC+ terminal powered by the battery. I do have battery voltage at the DC+, but don't get 13-14 VDC at WOT. It stays at 12V. Share this post Link to post Share on other sites
lynnmor 7,495 #19 Posted Sunday at 08:32 PM I've used the cheap eBay regulators and they delivered the correct charging voltage and never failed. Of course YMMV. 1 Share this post Link to post Share on other sites
Wayne0 741 #20 Posted Sunday at 09:01 PM Yeah, this was one of those. We'll see how the new one does. I can't see dropping $100+ on a branded one. Share this post Link to post Share on other sites
