Bob,

One problem that can result from using a switch that has high current contacts in a circuit with small current is the switch contact surface can oxidize and create a high impedance barrier. Small current will not be able to generate enough flow to punch through the barrier.

Unfortunately, you may not be able to discover the problem with a multimeter. Have you seen multimeters with dual continuity settings? The high setting has enough current to punch through the barrier while the low setting does not. That means the multimeter can lie to you if you use the high setting. The low setting was developed to overcome this issue. A secondary benefit is the low setting can be used to test low current diodes and transistor junctions.

Jim Fogle - 2025 BiaB (Build 1128) RB (Build 5) - Ultra+ PAK
DAWs: Cakewalk Sonar - Standalone: Zoom MRS-8
Laptop: i3 Win 10, 8GB ram 500GB HDD
Desktop: i7 Win 11, 12GB ram 256GB SSD, 4 TB HDD
Music at: https://fogle622.wix.com/fogle622-audio-home