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Re: (ET) Rookie questions on an E20
1. Should anything happen when I turn on the key? - i.e should any of the
relays click? Should the gauges show the charge state?
Yup. When you power the key, relays 1 and two should click in. It's a
soft sound, but is there. If you open the top of the relay panel you
should see them move.
2. I've found the seat and brake safety switches - are there any more?
Nope. If they are set (sitting in seat, brake on) then power is applied
to the two relays and the contactor bus is active and ready to shoot.
Assuming of course the disconnect is in.
3. When I press in the 'Disconnect switch' The gauges do show the charge
state and resistor elements get hot (nothing connected to the PTO). Is this
normal? Should the PTO contactor click?
Nope. The motor should *not* be on unless the pedal is down. And the big
front resistors should not get warm. Stop what you are doing, pop the
panel under the steering wheel and check your contactors; one is
probably stuck in the on position. tap lightly with a hammer to see if
they loosen up.
4. When I attempt to charge - with the disconnect out nothing happens
(except the transformer hums). with the disconnect in the resistors get hot
as before. Is this correct? (I can't see any change in battery voltage but
also can't believe the resistors should get hot during charging).
Once again, contactor is stuck.
5. Does anyone have a circuit diagram for the E20?
Bill Gunn has the manual. Get it. It is without a doubt the best
resource; it has *EVERY* schematic and trouble tree.
it will tell you everything.
6. I assume the large contactors are part of the motor speed control
system,
but what is the function of the relays at the top of the plate (behind the
switches)?
The relays control the response of the contactors to the various
interlocks. Seat, brake, switch, etc. One relay controls the lock-in of
the field weakening circuit, another controls reverse, and another
controls the cruise control system.
7. How does the cruise control system work? - is this the function of the
PCB's and components.
naah, it's as dumb as a box of hammers. Just holds in the 4th speed
contactor (full power, full field) bypassing the throttle switches. If
the throttle is blipped, or any of the interlocks are hit, the CC shuts off.
The only thing that matters on the PCB for getting the tractor going is
the two diodes to the bottom right. They are part of a set of four and
they provide the power to the field. The rest of the PCB is simply a
current comparitor that allows or shuts down the field weakening circuit
under high motor load. If it's dead speeds 6,7,8 are down, but that's it.
Like I said - I need help. - Once I've got it running I'll start on the
mower and blower...
Call Bill Gunn. He has all the answers.
Chris