Pull of the electrical connectors and take a 12V Test light. Put the pigtail on the +ve on your battery and check each plug by touching the electrical connection of the plug with your test light. Make sure not to not touch the body of the plug as it is always grounded.

1.0 If the Test light lights up brighly the plug is good.

2.0 If the Test light does not light up the plug is bad, change it.

3.0 If the Test light is dim, the plug is pretty much gone, change it.

Every plug I every had to deal with was either 1.0 or 2.0 above, a dim light (poor resistance) is rare and I have never seen one yet. I was always