Small Engines (Lawn Mowers, etc.): Blades quit turning - follow up, electric clutch, safety switches

Question
QUESTION: I have a White LT1850 46” rider with a 20 hp v-twin, overhead valves, dual carburetors. It was purchased new in 2002.

A few months ago, without incident, the blades quit shutting off when going into reverse. I wasn’t too concerned, as it was kind of a hassle anyway as cutting my lawn requires a lot of stopping and turning around. A few days ago, while going forward, the blades just stopped. I push the knob in and pull it back out and the blades again start turning. I might go 20 feet, it may be 200 feet, and then again they’ll stop again on their own. I can do this over and over.

All the pulleys on the deck appear to be straight and turn freely. The belts are all tight and in good shape. The battery reads 12.4 volts at rest, 14.4 when engine is running. I’ve checked all the connections I can find and all are tight. Seat contacts are clean and nothing is bent. My grass is growing very quickly. I don’t want to use my push mower on 4 acres. Can you please help?


ANSWER: Mower model number:  13BT616H190

When you checked the safety switches did you disconnect and reconnect each of the connectors?  I have had corrosion on the safety switch terminals cause weird problems.

Is the reverse cut-off switch on the shift lever or inside the tranmission?  I checked the parts diagram but there is no electrical diagram.
Let me know how many safety switches you have and where they are located.
Eric

---------- FOLLOW-UP ----------

QUESTION: How about the electric clutch? I have an electrical diagram and I've tracked down all the relays/switches. All were pulled apart and checked. All look OK. I don't have the equipment to actually test them, but nothing looked burnt or corroded. The reverse kill switch is on the shift lever. I put everything back together and took it for a test ride. Nothing is any different. Still just shuts off whenever it pleases.

I don't know if there's any way for me to send you a copy of the electrical diagram. I can scan it and email it. There is the contact switch under the seat of course. There's a PTO switch and a reverse kill switch. I don't know what you mean by where they are located. Do you mean on the circuit?

How would I test the electric clutch? Do you think that could be the culprit?

Thank you for your help.

Answer
The PTO clutch is composed of three major
components; the field, the clutch plate, and the friction
plate. The clutch plate always turns with the engine.
The field is a coil of wire on an iron core, which
becomes an electromagnet when power is applied.
The friction plate is the only piece that can slide up and
down on the crankshaft axis. It is normally spring
loaded so that it is not in contact with the clutch plate
and is pressed against the brake material opposite the
clutch. When power is applied, the friction plate is
drawn toward the clutch plate and the two rotate as
one.
Testing
If the electric PTO clutch is not engaging or is suspected as a cause of electrical problems, use the troubleshooting steps. These procedures will help you determine if the clutch has failed or is the cause of the electrical problem.
Coil Resistance Measurement
1. Disengage the PTO, set the parking brake, turn the ignition key to OFF and remove the key.
2. Disconnect clutch wire connector.
3. Set the multimeter or volt/ohm meter to check resistance (ohms).
4. Connect the meter lead wires to the wires in the clutch connector.
5. The meter should read between 2.40 ohms and 3.40 ohms. If the reading is above or below these
readings, the field has failed and needs to be replaced. If the reading is between these two
limits, measure the clutch current draw.

Measuring Clutch Current Draw
1. Disengage the PTO, set the parking brake, and turn the ignition to OFF.
2. Disconnect the clutch wire connector.
3. Set the multimeter to check amps (10 amp scale).
4. Connect the positive meter lead to the tractor terminal of the clutch wire.
5. Connect the negative meter lead to the corresponding wire terminal.
6. Connect a short jumper lead from terminal.
7. Turn the ignition switch to the “RUN” position and the PTO switch to the “ON” position.
8. If the meter reading is 3.5 amps or above, the system is functioning properly. If the meter
reading is below 3.5 amps, check the electrical system for problems (i.e., the battery, ignition
switch, PTO switch, or wiring harness may be malfunctioning).

Have you priced a new clutch?  I hate to say just replace it because they can be expensive and I see more problems with wires, connectors, etc., not delivering enough current to keep the clutch engaged.
Eric