The old saying, “When in doubt, change it out,” is not a good motto for HVACR service technicians. Guessing at a problem and randomly changing out components is never a good strategy, and it seldom works out well for the customer or the technician. Instead, technicians should strive to prove out their diagnosis and only changeout truly defective components. This can sometimes be accomplished by either temporarily jumping out the suspect component, bench testing the component, or performing an additional test to prove it is truly defective.
Defective controls are the easiest to verify. Simply jumping out the suspect control will verify if it is the problem. Be careful, though, because not all control components can be left jumped out. This is especially true of safety controls — they may be jumped out for a very short period to verify a diagnosis, but cannot be left that way. Use good judgment when jumping out any component.