(ET) FW: E20 Speed 8 broken

["Markus Lorch" <mlorch vt edu>]

Hi all,

got a little electrical problem that I haven't been able to 
solve on my E20 - 26AE20CC. 

While mowing last fall I blew the control fuse, replaced it
and blew the replacement again once I hit speed 8. Everything
worked (and still does) fine up to speed 7. I left it for
this winter to figgure out what is wrong. Here is
what I've done:

- visually inspect card 4 and card 3
- inspected the speed selector box, wires and micro-switches
- measured if I have a wire grounded agains the chassis
  ( I found a voltage potential, but virtually no current flow
   from any battery post to the chassis)

I looked at the troubleshooting sketch and there really shouldn't
be anything fancy about the FW-4 switch, which is connected to
card 3, connector 6 via a wire with potential 39. if the switch
opens (when we reach speed 8) the last field weakening resistor
(R7) should be switched in, thats all. 

One note: Does anybody know what the difference between the models
"26AE20CA and DA" and the "26AE20CC" is? I have the 26AE20CC tractor
and the troubleshooting sketch for "Models 26AE20CA and DA". Up to
know I couldn't find a difference. 

Any ideas on what to check next? 

Thanks guys

Markus