2140 clutch won't engage

[pat32rf]

My BIL has a 2140 that looks to be in good shape. I'm a retired electrician. As a result when something that might be electrical goes wrong I get called. Of course he has no manual or wiring diagram. This time his clutch for the deck won't engage.
The clutch seems to have a constant 12V feed and should pull in when the circuit is grounded in the little relay, which would drop out when you hit reverse or get off the seat, right? ( I don't use his mower so don't know how it should operate)
The clutch will pull in if I put 12V to it. The seat switch is jumpered out. He thinks that the reverse switch has been disconnected somehow at some point.
Is that little relay what controls the clutch?
Is the reverse switch a normally closed circuit that holds the relay in?
Is there any other switch (safety, interlock) that holds that relay closed, besides the main on-off deck switch on the dash?
The starter circuit will not operate if the deck switch is engaged. Is this normal or should the mower start but then you have to disengage and re-engage the deck switch to start the blades?
If I don't get this fixed soon I will wind up loaning him my red mower.....

 

[JTKub]

Sounds like you've got all the angles addressed. If the seat switch wasn't met, power wont go to the starter. There is a P-brake switch for the starter circuit as well. I've seen low battery voltage cause a no-go clutch, broken wires, etc. Not sure of the rev pedal switch is NO or NC, but it's possible something is up there. The engine shouldn't crank with the PTO engaged. Too much strain on the starter.

Joel

 

[OldMachinist]

Yes the relay is for the PTO and the starter should not engage with the PTO switch on. To understand the PTO circuit better download the PTO section and wiring diagrams of the service manual for the 1500 series mower here.
http://manuals.mtdproducts.com/mtd/DocGetter?doc=1000section39.pdf

It should be very close to the 2140 wiring.