Don't know what the resistance should be but if you jump across the contacts of the sail switch (thereby bypassing the switch) and it still doesn't work, the sail switch is not the problem. Obviously, you don't want to leave it that way as a solution but it will work for testing.
If that does fix it, your next step is to clean all the corners on the inside curves of the slats of the squirrel cage. I have found that enough dirt can collect to slow down enough to be the problem. I have used a small bendable bottle brush to get into those corners.
2004 Damon Escaper 4194 LX400
Freightliner XC Chassis,
Cummins ISL 400hp