I have an E-15 and an E-20. I'm not feeling so confident about be able to install the alltrax myself and all five of the relays in the E-20 have cracks across the metal bans so I think real estate will become an issue for the surplus center ones I'll try Harold.
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Tom, I don't think this is really the deciding issue for whether you should commit to an Alltrax conversion. There seem to be numerous candidates for replacement relays, and you'll still need one to implement the PTO return-to-off safety circuit which Alltrax doesn't show on their install schematic (but see http://www.elec-trak.com/forum/showthread.php?t=72 for how I did it). I haven't gotten around to installing the one I got from Surplus Center -just in case- but I'm satisfied from its specs that it will work.
Alternatively if you want to bypass this safety circuit like Alltrax implied is OK, you can get by with only one of this style relay in your ET. So if one of your OEM units fails, you can bypass the PTO RTN circuit and continue with the good relay in the other circuit.
Having said that, I am still a big fan of the Alltrax unit. It does basically drop in to the E15 with no significant mods save whatever changes you decide to make to access the 0-5K pot.
Joel