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Hello Eric,
I have an Ariens YT12H40 lawn tractor purchased in 1994. It is model 936003 and has a 12.5 HP Tecumseh engine. While tracking down a shorted wire that blew the 10 amp fuse when the electric pto was engaged, I came across a resistor in line between one "molded diode plug" coming from the charger and the 10 amp fuse on the other side of the resistor. This circuit eventually traces back to the battery, so I am assuming it is the charging circuit. The resistor is 1 and 1/16 inch long, about a 1/2 inch diameter, looks like a cylinder with a flat bottom, has 8 or 9 cooling fins and has a 1/2" long connector on each end. It appears to be "brass like" in appearance. The resistor is not mounted to any surface, but is "floating" in air space, held in place by the wire connections on both ends. After repairing the short and making connections, the mower and pto run fine, but the resistor gets extremely hot...in fact too hot to touch without burning oneself. I measured the resistance and found it to be about 1 ohm, after taking into account the resistance in the meter and probes themselves. After talking with several Ariens/Tecumseh repair shops, no one seems to know what the values of the resistor are (there are no visible markings left, they "think" it may be 25W) and do not know if it normally gets hot enough to burn oneself or not. The fix is a "buy one and see" approach. The price of the resistor is around $55. (Part # 03619300)That seems a bit high for a guess. I replaced the diode directly between the charger and this resistor with no apparent difference after one tech suggested a diode failure in the charging circuit. (The other diode coming from the charger,and on a branch circuit from this one, is in the light circuit, I assume acting as a DC rectifier for the lights.) I did perform voltage checks in several locations and the voltage coming from the charger through the resistor varies from 14 to 17 volts. The voltage at the battery when the engine is running is about 12.9 volts. (The battery may be a bit low...we have been running it with the resistor removed and the charging circuit open to allow us to finish some work.)
Any help at all would be greatly appreciated. I'm trying to call Ariens and/or Tecumseh but to no success at this point. Thanks greatly. Bob
Answer -
Is the resistor an Ariens part number?
I checked the Tecumseh repair manual and it doesn't say anything about a resistor so I'm not sure exactly why it's there. From what you described about the resistor, it's physical size and cooling fins I'd assume it would get extremely hot especially at 1 ohm. I have some old tube radios that have big ceramic resistors and they get extremely hot just as you described.
Let me know about the part number and I'll see if we have a repair manual. I'll also ask some other techs at the shop to see if they have ever come across this risistor.
Eric
Wow such a quick response!!! Thank you. The part number is from the Ariens Lawn Tractor Service manual that I ordered seperatly some time ago. I do have the schematic diagram of the circuit that can be sent to you via a jpeg if that would help. (Can I send attachments through this service?) Anyway, the part is simply labeled "Resistor" and the Ariens part number is 03619300. That part also is listed in the Ariens web site, but with no values, description, or anything else. The manual also states that it is a 5 amp, unregulated charging circuit. The 1 ohm is what I am currently measuring. I don't know what the original value was, or should be.
Again, thank you for such a speedy reply. I appreciate your effort already.
Bob
AnswerI checked the repair manual but like yours it provided very little information. I also asked 2 other technicians that work at the shop and they can't recall every replacing a resistor on an Ariens...and we're an Ariens dealer.
I wish I had a solid answer but the best I can say it to run the mower the way it is. I highly doubt that you will damage the alternator or any other parts.
Have you tried asking anyone else on the board? If you do find an answer please let me know.
Eric
