1872 starter and pto problem
 

I'm totally new to owning a cub and semi proficient in troubleshooting, but I sure could use your expertise. I picked up an 1872 gas cub for a song and really want to get it going. When I first brought it home, it wouldn't start with the key nor would it jump via the solenoid. I was able to put a jump pack directly to the starter to get it to start. I mowed my land with it and I was happy. Being lazy,I jumped the starter a week later and began cutting the grass again. After about 30 minutes I noticed that the the blades quit running. I thought I bumped the pto switch, so I attempted to re engage it with no results. Since I had been cheating to get it started anyway, so I figured that maybe the PTO switch had been my starting problem in the first place and finally the switch crapped out on me. Easy enough, I replaced the PTO switch. Still no good. I tested the seat switch and it has good continuity. I tested the brake switch and it has good continuity. I tested the ignition switch and it has good continuity in the off position, run position and start position. Any ideas?

What is the battery voltage with engine stopped? then running @ full throttle?
Should be 12.5 V. stopped and maybe 13.5-14 Volts running.
If not you have a charging issue.
Also look @ fuses
I don't have a wiring diagram here to see if you have a forward/reverse switch or if your system has a PTO relay that may be bad or???
All things for you to check.
You need to start @ the reason it will not start by following the power path through each component.:beerchug:

12.84 volts at stop and 12.84 volts running. Having said that, I sure could use some further help in determining what is associated with the charging system as I am ignorant on these. Thanks in advance.

I would be looking at your Ignition Switch. The Ignition Switch effects both the starting and PTO circuits.

Not sure where to start as it seems pretty expansive or a troubleshooting task. Any advice would be appreciated. I believe it's a charging issue.

Things I've replaced today and still haven't solved my problem: starter switch pigtail, starter switch, battery, starter selonoid. Tractor still starts when I put a jump box directly on the starter, but PTO still won't engage.

Did you get the correct switch for the 1872?

Yes. Ordered it from the cub cadet dealer. It showed up today. Still won't start with the key and PTO still doesn't engage.

@ this point it sounds like you are throwing parts @ it in hopes of winning the lottery.
Possibly you need to follow the wiring diagram, systematically eliminating each
circuit till you find the no power area and fix it.
This is not an electronic magic box thing, it is a simple electrical system.
follow the power till it stops and find out why and correct it.
Not trying to sound like a jerk here, a simple $5 meter and test light should do just fine.:beerchug:

yep need to chase the power thru all the switches and find out where its dropping out.

Sorry for the long-winded post. :BlahBlah:

Ok... going back to basics, sounds like you could have several problems. A charging problem and a wiring or interlock/key switch problem that prevents starting. Let's just work on the starting problem here. Check the fuse on the front of the dash below the steering wheel and make sure it is good. If it is good, put it back in, then raise the hood. Now, turn the key to the first position (running with lights on) The lights should come on. If not, check with a meter to see you have 12V on the connections on the back of the Ammeter. If good there, you should have 12V on the back of the keyswitch on the black wire feeding the keyswitch. If not trace out where you are dropping it. On the back of the keyswitch, you should also have 12V on the white wire (alternator) and the blue wire (lights). If not, you may have it miswired or a wrong or bad switch.
Now if the lights come on on the first position, have a helper turn the key to the start or turning over position (just like in a car). If it does not turn over, check the back of the key switch for 12V on the red wire, this winds up telling it to turn over. If no 12V here, bad or wrong or miswired key switch. If you have 12V here, next make sure the PTO switch is in the off position. Try starting again. Still not turning over, check the back of the PTO switch, for 12V on BOTH red wires (terminals C and D - WHILE TRYING TO TURN OVER VIA THE KEY SWITCH) If you have 12V on terminal C but nothing on Terminal D with the switch in the off position, you probably have a bad PTO switch. (This caused a no start recently on my 1772) If you have 12V on both terminals ( C & D - red wires on the PTO switch) check the brake switch next.

Remove the tunnel cover and check the brake switch, (my father's 1872 failed to start because of a broken paddle that presses the brake switch).

Above all be very careful not to get caught or wound up in any rotating or moving parts while troubleshooting this problem.

Starting at the other end of the problem, If you lift the seat and quickly jump 12 to the SMALLEST singly attached wire on the start solenoid that is located along side the battery, this will tell you the solenoid is good and the problem is probably in one of the switches mentioned above.

Good Luck.

Thank you so very much for the detailed troubleshooting plan!! I will let you know what I find out. Thanks again!