mswyka Posted May 16, 2006 Posted May 16, 2006 Last Friday I went out to the shed intending to fire up the old 7790 and mow the lawn. When I walked into the shed I was surprised to find that the low oil pressure light was lit. Thinking that one of my kids left the key on, I checked to see if there was enough juice to crank the engine. The key was in the "off" position, the engine started fine and ran fine with no light on while I cut the grass. When I was finished, I turned off the tractor. No light lit. After a few minutes the low oil pressure light lit again. I now have the battery disconnedted. Any better suggestions?
HubbardRA Posted May 16, 2006 Posted May 16, 2006 It sounds like the light is hooked to the wrong terminal on the switch. It must have power all the time, if it burns with the switch off. It should be hooked to switched power, so it doesn't burn when the engine is shut off. Usually the power goes from the ignition switch directly to the light, then the oil pressure sensor connects the ground when the pressure drops below a specific level.
UCD Posted May 16, 2006 Posted May 16, 2006 The oil pressure circuit is on terminal I of the ignition switch and receives power from terminal B with switch on. The problem Could be a bad pressure switch shorting to ground with switch in off position as this is where the oil light is supposed to get its ground if there is low oil pressure. Could also be a shorted ignition switch. [img]/club2//attach/UCD/7790OilPressure.jpg[/img]
2burning Posted May 16, 2006 Posted May 16, 2006 I vote for bad ignition switch, or somehow power is getting onto the Brown wire, possibly from the regulator, or like what was mentioned a chaffing wire. A bad engine or frame ground can cause weird current flow too. It sounds like the oil pressure switch is doing it's job? (I guess it's doing it's job much too well :> )
mswyka Posted May 16, 2006 Author Posted May 16, 2006 So if I am hearing all this correctly, since this is the first time this has happened, incorrect connection is less likely than a chaffed wire, a shorted ignition switch, or freak behavior in the voltage regulator. The wiring diagram is very helpful. I will trace this out and see what I find.
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