FIRST, ensure power is OFF. SECOND, if you have an AUTO-START make sure it's OFF.
THIRD, check with a meter BEFORE working on it. Since you've already been in there most likely you know what you're doing, just be extra safe.
Mine is an ESCO ES-50 with built in Surge protector. Have you checked the contactors? There are two and usually one is all you'll need to replace rather than changing out the whole assembly. Good luck....Dennis
ES 50 Surge