Fan High Speed Issue

[gschroeder]

I have a 1970 CST-10 with factory A/C. The fan works fine on low, and medium. However, the fan sometimes does not work on high. Sometimes it works on high just fine, and sometimes not (when its not working on high the fan is not moving at all). I double checked the ground wire on the blower motor, and it is hooked up with a good ground on both ends. Any suggestions on how to trouble shoot this? I did a some research on this problem, and it appears the "Blower High Speed Relay" may be bad. I see LMC actually calls the part "A/C Blower Relay" for $12.95. Thank you for your help in trouble shooting this. Thank you