Craftsman 17HP 42" mower wiring question

[wheelerjb]

I've been limping along my craftsman mower(model 917.272084) for quite some time and it finally gave up the ghost. When I got the mower several years ago, the 6 pin connector from the motor to the main harness was toast. it was a melted blob of plastic. FYI, this connector connects the ignition, fuel solenoid, and voltage regulator to the main harness. I cut the mess off and rewired but it would keep burning the connectors that traced back to the AC legs on the regulator. Long story short, the mower died a spectacular death last week by melting about 80% of the wiring harness in seconds. Its my fault since I hardwired past the fuse somewhere along the way, but looking back I think the regulator may have had something to do with it. I have replaced it anyway to make sure.

I purchased a new harness and still have to connect the motor electrical, but found something interesting along the way. The AC voltage at the regulator is also directed to the main harness and then to a relay. According to the manual schematic, the relay connects the two AC leads together, I think when the mower is running. However, the new harness, as well as the old, are not wired per the schematic. For example, the schematic says yellow wire to 87a and the other yellow wire to 30. The harnesses have the alternator connected to leg 87 and 87a. At no point in time will they ever be connected.

Does anyone even know why the alternator would be connected to itself through this relay? It makes no sense to me? Perhaps the harness is wrong and that's why it has been having issues all this time? I have been running it for a year without the AC wires connected to the relay. I found some other schematics for craftsman mowers that don't even have this set up. Any ideas?

link to manual with schematic, see page 33. http://www.hammerwall.com/Download_Manual/5630/

Thanks,
Wheeler

 

[wheelerjb]

I installed the new harness today and just wired everything up. So far it works and hasn't smoked anything, yet. I'm still not sure about this regulator business though. The only thing I have connected to the mower from the regulator is the middle pin, DC output. I don't have the AC legs of the regulator connected to the harness. I'm too scared and don't want to smoke my $120 harness.

-I read somewhere the alternator coil resistance should be .2-3 ohms?, it checks .2ohms.
-Each leg is insulated and not shorted to ground.
-The output at 3600 rpm(verified with timing device) should be 28VAC, but I get almost 42VAC from the coil!
- The new(and old) regulator are outputting 15 volts when checked at the regulator, but it is reduced to 12.8 when checked across the battery. There is a half volt or so drop when i disconnect the regulator.
-The amp meter says 12-13 amps and verified it with my amp meter. my probes get hot too, which is strange.
- The 田harging wires get really hot and if the motor runs for more than a few minutes, you can't touch them. This is my concern...i'm just going to burn the harness again. :frown:

any suggestions?

 

[wheelerjb]

ok, I figured out if you connect the alternator wires together, it essentially "locks" the motor. so if the wires are connected per the diagram through the relay, when the operator stands up, the motor will shut down quickly as the alternator will act like a brake.

I find it odd the harness is not wired per the schematic, maybe something was changed and not properly documented.