Why the old relays and contactors need to be replaced when they are still functioning?
Electrical relays and contactors are designed to open and close a certain number of times with a particular current load, before the contact points are totally damaged, they should be replaced when they reach a certain point. The pitted point of relays or contactors will lose voltage. If a motor running in voltage lower than its design point, it will draw too much current that more than it can handle. If motor runs in this situation, eventually the compressor motor or the fan motor controlled by the relay or contactor will burn up and require replacement.
