Sunstar tractor oil light

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  #1  
Old 09-23-18, 10:18 PM
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Sunstar tractor oil light

I posted several months ago about an oil pressure light that stays lit all the time on my 1995 Simplicity Sunstar. There was a new oil pump installed last year when it was rebuilt, and it has run fine. (1962135) 20 hp kohler engine. Having to repair a toggle switch forced me to expose all the wiring under the dash so I could see if there was a broken or inadvertent grounded wire and I can not find any problem. I have tried two new oil pressure switches with no improvement. If my science is correct Power to the light makes a circuit when the switch is not being pressurized by the oil pump due to failure so as to warn me. (if the engine is running) So where else can this circuit be completed besides the switch or an inadvertent ground of the wire that goes from the light to the switch?
 
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Old 09-23-18, 11:27 PM
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The light doesn't change whether you ground the wire or unplug the switch? If not, then something in the wiring pretty much has to be it I would think, unless there is some relay or other switch the wire goes through.
 
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Old 09-24-18, 10:04 AM
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Hi Chuck. If I unplug the wire (with the engine running of course) the light goes out, which screams that it is a pressure switch that is not working, but I have tried one NEW pressure switch, two others I had access to, and put a borrowed pressure guage on it that indicated 30 plus pounds of pressure.
AND as I said it has a new oil pump in it and has been running like this for a year. If a ground makes the light stay on, then I have to find the spot where it is grounding besides the switch. I will keep looking....
 
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Old 09-24-18, 12:05 PM
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If unplugging the switch makes it go out, then check your switch resistance with an ohmmeter. The wire isn't grounded out or it would have stayed on. Your switch needs to have continuity with ground with the engine off (no pressure) and it needs to be open with the engine running.
 
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Old 09-24-18, 12:58 PM
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Chuck, that is what is driving me nuts. All of the switches I have tested so far have full continuity with ground, but they are (apparently) are not opening up with pressure applied (engine running)
 
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Old 09-24-18, 10:40 PM
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Do you have regulated air? If so, put 30 psi or so to the switch with a rubber tipped air blower or screw the switch into the air line and see if they break contact with pressure.
 
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Old 09-25-18, 11:48 AM
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The air pressure will break the switch. I started the engine with the switch still on the bench just to see what might happen. Oil was pumping out of the top of the block (gauge hole) It was not "spurting" out, just sort of running out over the edge of the hole. It was a new pump last year, but I won't be the first guy to get a bad one out of a box I suppose. I will need to borrow a tester again to check the pressure I guess
 
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Old 09-25-18, 06:05 PM
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Sunstar Oil Sentry

I got into the service manual for this Engine and found that this engine either has an "Oil Sentry" or a pipe plug in the hole in the engine. Assuming that this switch might not be an OIl Sentry Switch, but a normal oil light sending unit, could that be why the reading is contantly on?
 
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Old 09-25-18, 08:28 PM
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Oil pressure Switch

i have found a Kohler Part # for an oil pressure switch for this engine CH20-64512 Pn 2509927s and have one on my bench. It will not trip with the engine oil pressure but will with Air pressure. I had to move the tractor and forgot the hole was open. the oil pump pushed out almost a quart of oil onto the floor before I got it stopped. I guess I need to know what the pressure rating is on this Kohler pump in order to test the switches. it sure looks like the pump is working....
 
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Old 09-26-18, 01:01 AM
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I don't really know what the oil pressure is on these but I would think 7 or 8 psi would be be acceptable low range and who knows what top of the range would be. I would expect the switch to come on if pressure got under 5 psi.
 
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