There is some misinformation in this thread about how warn winches are wired. I know, older thread but at least I'm not the only post this year.
Warn solenoids are in what is called an H bridge configuration. Not your standard mag motor H bridge but a series wound H bridge.
Warn does not switch the ground lead! The ground lead goes straight from the battery to the motor!
More importantly: The solenoids are not in parallel. They are in series. This does nothing for lightening the load on them!!!
Look at this picture:
Warn motors have 4 lugs. The 4th lug not shown in this picture goes straight to the battery negative. Between terminal C and the ground lug is what is called your series field. You know how a regular dc motor has magnets? These motors dont have permanent magnets around the can, they have electro magnets attached to the ground stud and C, and those electro magnets are powered in series with the armature.
Terminals A and B are your commutator brushes like on a regular DC motor.
Winching in trips solenoids 2 and 3. Power flows from the battery + through solenoid 3
to the B post, through the armature, out the A post, through solenoid 2
, to the C post, through the series field, out the ground post, and back to the battery. Those solenoids are in series!
Winching out trips solenoids 1 and 4.
The moral of the story, you only need to know this part if you read this thread and dont understand circuits that well:
If you feel extra solenoids should be carried then carry them, don't think you are carrying 2 "prewired spares." If any one solenoid fails, your winch will not work in that direction.
Personally I fully understand the circuit and I could make the winch work if all 4 solenoids burnt out and I lost my remote using my booster cables, so I would not carry spares.
I believe the 2 solenoid setups use double throw solenoids. If you will imagine a solenoid as an on/off switch, a double throw solenoid is an on/off/on switch. Same circuit.