cub cadet 682 electric problem

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cub cadet 682 electric problem

Postby electromech31 » Sun Jun 09, 2019 6:12 pm

Hello guys
My 682 is not engaging the electric PTO, checked gap .015, New Switch, connectors were loose on switch replaced, battery has plenty of juice ,engine runs.
So I used the Manual and rechecked wiring in switch and had to move a few, Now when turning key and having brakes locked down switch turns on starter and engine turns over.
Is there a Good electric schematic for a 682 1980.
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Re: cub cadet 682 electric problem

Postby DaveKamp » Sun Jun 09, 2019 7:56 pm

Hi Elmer!

Well, I don't have any schematics at my disposal here, but I had a pair of 782's, the 682 clutch circuit should've been about the same...

If it were me, I'd put a test lamp or buzzer on the clutch hot lead, and ground the other, then see if you get a light. I don't recall what safety switches the 82's had, but standard op positions of Ignition on, brake released, drive in forward, sitting on seat SHOULD yield a clutch engagement.

If not, do a test application... engine off, apply battery to clutch... you'll hear it WHACK! when magnet energizes.

If you don't get the whack... check chassis ground and clutch ground wire, as they're likely suspects. PTO clutch contacts and safety switch contacts go south as well... and wires (stranded) take every opportunity to wick up moisture by capillary action and become fuzzy green resistances... and that clutch coil needs unimpeded current.
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Re: cub cadet 682 electric problem

Postby cholloway » Mon Jun 10, 2019 10:25 am

Have you checked in the above Documents and Manuals section?
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Re: cub cadet 682 electric problem

Postby electromech31 » Tue Jun 11, 2019 9:30 pm

I did connect a battery charger and the Clutch snapped.
I also looked thru the documents for 682 electrical schematic I may have missed it.
Thanks Guys
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Re: cub cadet 682 electric problem

Postby DaveKamp » Wed Jun 12, 2019 10:54 am

Okay, well, clutch snap is a good thing for your clutch. Be careful, though, using a battery charger for powering clutches... here's why:

The clutch is an electromagnet, and being such, it has a very high inductance. Inductors build large and intense magnetic fields when current flows through, but when that current is disconnected, that magnetic field collapses. As the field collapses, it attempts to generate a high current flow between it's leads, but with leads disconnected, there's no way for current to flow from one lead to another... it's an open circuit. As a result, voltage across the two leads rises to a very high point, very, very quickly.

(This is exactly how an ignition coil works, by the way... it just includes an additional winding, with many, many, many more turns on the high-voltage side)

The inductive snap from the clutch being disconnected, could easily break several hundred, to mebbie a thousand volts, which in most cases, is a whole lot higher than the battery charger's circuitry can handle. Older battery chargers consisted of a transformer (to step 120v down to around 10vac) with a center-tap, and two diodes (for full wave rectification) to yield around 14.2vac. Fancier ones used SCRs instead of diodes, and a crude gating-circuit that was voltage-sensitive, to provide some simple over-charge limit control. Typically, the diodes or SCRs used, were good to mebbie 25 or 50v max. Newer 'switching' type battery chargers are a whole lot more complicated, but still, the output rectification and controls are good for about 50v or so... so popping that clutch with a battery charger is an excellent way of zortching the charger... better to use a pair of jumper leads from the battery... you won't hurt it.

The PTO switches are frequent offenders, as are the wiring to the clutch (they're stranded, and can wick moisture by capillary action, corrode to green fuzz about a foot or three up from the connector. Ground wire from battery to chassis is often bad (even when battery to motor is good).

And for what it's worth... a bad clutch connection can sometimes (because of inductive kickback noted above) bite the regulator rectifier on the engine... if the machine's battery cables are poor, or the battery becomes disconnected. The presence of the battery tends to absorb most of the clutch's beating.

In industrial circumstances, electric brakes and clutches appear on all sorts of motion control and machine tools, electric elevators and escalators, overhead hoists, augers and conveyors. SOME of these are DC, and some are AC, but in all cases, whatever's controlling them is typically a relay or contactor, and because of the inductance, that relay or contactor is susceptible to long-term erosion from arcing when the clutch/brake coil's circuit is broken. Oftentimes, there will be a resistor across the coil's leads, and sometimes a capacitor, for the purpose of 'snubbing' that high-voltage kickback. In DC applications, a diode is placed across the leads, in reverse-bias (so that when energized, it will not flow current around the coil), so that when the clutch is de-energized, the collapsing field's current can have a one-way path around. This is commonly referred to as a 'free-wheeling diode'.

Reason I'm pointing this out, is because most lawn mowers do NOT have any sort of snubbling or freewheelling diode... and this means that PTO switch's life is somewhat limited. Everything ELSE in that circuit... safety switches on the clutch/brake, the seat... anything that can 'knock out' the PTO in the interest of safety... can be subject to rapid contact erosion... and once the contacts are burned, that clutch will cease to function properly.

My dad's JD mower tractor kicks out the PTO every time he backs up... it, and the seat switch, are all wired directly in series with the PTO switch, and that silly 'back up switch' cycles the PTO, and burns out WAY to fast... it eats a switch every summer and a half. My Bobcat commercial ZTR doesn't drop the PTO, but it kills the ignition if the controls are put in an improper position, OR if there's no operator on the seat with the PTO engaged or parking brake not set. Now, this would be a particularly annoying feature, because the engine would kill every time I hit a bump, or leaned on a hillside, but the machine has a 'timer' that bypasses the seat switch that 'holds' the kill relay in run state a seconds and a half, so that it will not be falsely triggered by me bouncing through rough areas. I don't recall how the 82-series machines were set, but if your controls were knocking out the PTO frequently, those switches, or the PTO relay (if there is one) are most likely well-burned inside.

If you take an ohmmeter to the contacts, you will be able to find out wether a switch's contacts are making contact, but you won't get an accurate representation of the QUALITY of those contacts. At the meter's miniscule signal, those switches may look great... but under load, it won't carry much current. If you see discoloration or melting of wiring or switch, that's a sure sign that the contacts are marginal and getting hot, hence, likely a problem spot. Same goes for grounding connections on smaller wiring. Big wires can be marginal without giving such a clear hint.
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Re: cub cadet 682 electric problem

Postby SWilliams » Sun Jun 16, 2019 4:15 am

682 wiring, match the diagram to your serial number

Early 682.pdf



Late 682.pdf
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