Jumo 0 #1 Posted August 12, 2011 While plowing my garden my oil pressure light started blinking. I just change oil with only 2 hours on it. First I've checked the oil level and it's full. My manual only says not sufficient pressure at the oil pressure sending unit. I did a search on the forum. I read about bad connections, dirty breather and dirty air filter. I cleaned the breather with mineral spirits and installed a new air filter. I checked all the connections I could. I'm feeling a bit silly here, but I don't know where to look for the oil sending unit. I'm hoping someone can help. Are there any other things I should check? I've only run the engine about 30 seconds since it started blinking, but it does run just fine. (20hp Onan) Share this post Link to post Share on other sites
boovuc 1,090 #2 Posted August 13, 2011 Hey Jumo, The oil pressure switch is located behind the engine tins on the block just above the oil filter. Part #NN10824. Hope this helps you out. BooVuc Mill Hall, PA Share this post Link to post Share on other sites
Jumo 0 #3 Posted August 13, 2011 I should've started with the Toro parts viewer. I found the oil pressure sensor in the assy diagrams. You need to pull off the fly wheel shroud to get to it. I read a spec online that the sensor itself needs at least 2 PSI to function (turn off light). I have a carb leak-down pump for testing pop-off pressures onn 2 cycle carbs. I connected it to the sensor, pumped it up to just a bit over 7 PSI and the blinking light did not go off. I think the sensor might be bad. Is this a valid test? (See pic) I turned the motor over and oil just gushed out of the oil port where the sensor installs. It looks like the pump is still working. I guess I'll try a new sensor. I think I could get a pressure gauge on the oil pump. I think it'd be wise to make sure the oil pressure is in spec. I'd imagine if the pressure is over 2PSI I should be good. Can anyone confirm? Thanks, Share this post Link to post Share on other sites
sorekiwi 761 #4 Posted August 13, 2011 I think it'd be wise to make sure the oil pressure is in spec. I'd imagine if the pressure is over 2PSI I should be good. Can anyone confirm? Thanks, According to the (Wheelhorse) Onan Manual, oil pressure should be >8psi @ 1500 rpm with the motor at normal operating temp. Share this post Link to post Share on other sites
BOWTIE 226 #5 Posted August 13, 2011 HELLO, I USED A AUTOMOTIVE SWITCH ON 314-8. LIGHT COMES ON WHEN LESS THEN 3PSI. I USED A PS15 STANDARD IGNITION NUMBER. IF YOU NEED A DIFFERENT THREAD (1/8" or 1/4" PIPE THREAD) OR ELECTRICIAL CONNECTION (SPADE or THREADED STUD) IT IS EASY FIGURE IT OUT. IF YOU NEED HELP I WILL GET YOU A PART NUMBER, I DID PARTS FOR 35 YEARS. IT WILL BE A LOT CHEAPER THEN ONAN. BOWTIE IN COLUMBUS Share this post Link to post Share on other sites
Jumo 0 #6 Posted August 13, 2011 Thanks for the info sorekiwi. I checked the pressure and it is running at 15PSI at 1500RPM. As I suspected it had adequate oil pressure. So I tried the changing sensor. Bowtie I took your advice and put in an automotive sensor. Changed the terminal to a push-on Installed it and insulated the exposed connection. Now the sensor functions, but it didn't take care of the flashing light. It runs fine. I have a bunch of automotive light bulbs as spares. For the meantime I'm going to hook up my own dummy light. By tapping into the sensor and wiring it to the light bulb I'll be able to finish plowing and know for sure if the oil pressure goes low. If anyone has any ideas where to go next I'd appreciate the help. Regards, Jared Share this post Link to post Share on other sites
BOWTIE 226 #7 Posted August 14, 2011 THE NEXT THING I WOULD DO IS SWAP SOME OF THE RELAYS AROUND. ON MY TRACTOR ALL 4 RELAYS ARE THE SAME PART NUMBER. JUST A TRAIL AND ERROR METHOD. IT MIGHT BE THE CIRCUIT BOARD OR BAD CONNECTION. GOOD LUCK. BOWTIE Share this post Link to post Share on other sites
boatman 3 #8 Posted August 19, 2011 :thumbs2: you could always T the pipe where the oil sensor is and hook up an oil pressure guage as well as red light. That way you could tell your true oil pressure at any time. Share this post Link to post Share on other sites
Jumo 0 #9 Posted August 19, 2011 My neighbor a few doors down has a 520H. He was nice enough to let me swap out the 6 light circuit board with his for a quick test. His board in my tractor functions just fine. So something must have failed on the board. I'm cheap and won't spend $164.00 for a new board. I may just put a gauge on it. Share this post Link to post Share on other sites
Craig Arndt 6 #10 Posted August 30, 2011 Mine just started flashing this summer. I checked the oil level and such, I think it is likely something similar. It doesn't do it all the time, but most of the time. Its likely the control panel, the pressure switches usually last. I'll try cleaning it up and see what happens. Share this post Link to post Share on other sites
Gravelyguy 0 #11 Posted September 30, 2019 I just went through all this on a friend’s 520H. The sender was faulty. It would open the OP circuit around 65PSI ! The original switch is no longer available, even from Hobbs (the maker). If you use a single terminal automotive sender, it’ll work the lamp but you lose the circuit that powers the hour meter. That circuit is normally open and closes to ground when the engine has oil pressure so the hour meter won’t click away if someone leaves the key on. Nice feature. I used a Balkamp BK7011591 from Napa. Its a 3 terminal switch and as such requires adding a ground wire from the “C” terminal to a good ground. I used the nearby timing cover bolt. Works as intended and opens @ 4PSI. Share this post Link to post Share on other sites