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John Deere 318 not charging

Mike Following all of the very helpful posts I have isolated the no charging problem to the stator or the voltage regulator ($70@NAPA ouch). I'm getting 40 vac of of the stator w/ wires disconnected from regulator, no short to ground on either lead but .5 ohms (digital v/om) between the two leads. Nearly 0 vdc on center tab of regulator at full speed. Is there a way to check the voltage regulator off of the engine? What does the .5 ohm as opposed to .10 - .19 mean? Is .5 way too high? If I have to dig into the stator how do I go about it?
Dale G. Basgall Mike : Connect the regulator and run the engine at high idle, put the (dvom) on the ac scale and test the AC voltage at the regulator with everything plugged in. If your AC voltage is still there then the regulator is incorrect or is not working for some reason.

The device you are calling the regulator is technically called a rectifier regulator and as the AC voltage passes through the rectifier diodes it is then regulated by a chip inside into the battery of the machine. Typically at full speed of the engine and or high idle as John Deere states the AC voltage is dropped in half and then polarized + or - depending which side of the diode it goes out on, so anyway if your AC going into the regulator is 30 with it plugged in then the output of the diodes would be half of that in DC votage and then into the regulating chip and out to the battery of the machine.

John Deere has a test in their service manual for the voltage rectifier regulator but it's really not accurate 100% of the time and depends largly on the skill level of the tech using the meter.

.5 of an ohm is not high at all, however you are dealing with induction coils. What it boils down to is that if there is adequate AC voltage at the rectifier/regulator AC terminals with the device plugged in it's simply a matter of the rectifier regulator if there is little or no output at the DC terminals of the rectifier/regulator.

Should you want or need any other info please write back on the forum.

Dale G. Basgall

Tony Bachler I repair a fleet of 318 Garden tractors; The electrical system is probably the simplest system on the tractor. If it is understood; I'll walk you trough it. #1 The stator produces AC. AC swings equal Voltage of center line. This means Engine running at moderate rpm, potential differance between stator leads is 40 volts. The rectafierwill DO THIS;; it devides the voltage and makes dc = 20 this would be apperant power, however we can only use true power. Which is .707 of apperant power = .707x 20ac =14.14 DC. and that makes the battery a very happy piece of equiptment, Now in the regulator/rectifier there are 2 zanor diodes They do not lit the current flow back into the rectafier. I like to refer to it as a check valve in your water pipe. Ok we have the solution, How/what happened to cause the problem.the most one I see is some one jumping the battery #1the leads hooked backwords Just one small spark. The rectafier is history. If you are reading 40ac , your stator is ok With it pluged in to the reg/rec Your DC Reading with a low battery.Should be 14.12, this is controled be the state of the battery ;; Hope this helps you,TONY
Andrew Lange I have a simmilar problem as my 318 bat light is on and as i am cutting and if i stop pto it won't engage untill i charge the batt. the left and center lead are reading 26 on ac and the right lead is 52 ac. Is it my stator or rectifier?
Bob Holland My 318 had this same problem for many years and I tried everything to correct it. However, I did finialy find the problem. It turned out to be a bad connection in the three wire plug located on the engine harness near the voltage regulator. I replaced the connector and my unit has worked perfectly since.

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