I am working with an existing design and seeing a 200Ω, 2W resistor becoming discolored in the field (customer questioned its condition), but not appearing to fail. I measure resistance and is 203Ω, maximum measured voltage across this resistor 3.5V. That’s .06W, this is a 2W resistor. The resistor is not hot to the touch at all. My thinking was possibly moisture, but there are many other resistors on the board and none look like this.
The purpose for this resistor in the circuit is to prevent the input voltage to the +5VDC liner voltage regulator from exceeding its maximum allowable (35VDC). There is one relay powered off of V+. So drop across said does vary from 2VDC (relay off) to 3.5VDC (relay on).
Has anyone seen this or have any input as to why this is occurring?