(ET) contactor question

[tbamc <tbamc gbta net>]

I'm trying to resurrect a Toro "Carefree" 24v push mower, and it's not 
too carefree at the moment.

I've got 25+ volts at the contactor, and the motor works when wired 
direct, so I'm suspicious that the contactor is toast, but it's a little 
different than the E-T contactors so I'm not sure.

The contactor has two small studs, which have small + and - wires to 
them.  There are then 2 large studs on each side of the contactor, plus 
2 large studs on the top of the contactor.  There is 25+ volts at both 
the + small stud and one of the large studs on the side.  The other side 
stud is jumpered to a top stud.  The other top stud has a large neg. 
wire from the battery. 

What's confusing me is that when it should be 'on' there is 23.5v at 
both top studs (one of which has a neg. wire), and when 'off' with wires 
disconnected, there is continuity between the top two studs.

It seems to me that I have an internal connection between the top 2 
studs that shouldn't be there, but does it make sense that it could fail 
that way?  Or am I not thinking about this correctly?

If it sounds like the contactor is bad, is it possible to use an E-T 
contactor as a replacement?  How would I hook it up, with only 4 studs?

Thanks.

Thon