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Troubleshooting: Facts, Fiction and assumptions

 "I assume the circuit board is bad because it is the most complex part of the equipment. Besides I have a friend who seems to replace a board every year"
 Fact !? Unfortunately you might be right. The board is made up of 50 or more parts which don't really like temperature extremes, vibration or weird voltages etc. The rest of the equipment has a few wires, two or three switches and safety devices. When a board is replaced, the rest of these items should be checked for proper operation before the job is finished.



Fuses:
 A significant percentage of Dinosaur circuit boards returned under warranty have no failure or only a blown fuse. That means the equipment they were removed from probably still has a problem somewhere!

  1. When replacing a fuse, use one that has the current and voltage rating specified by the equipment manufacturer: The last person might have installed the wrong value.
  2. Visual inspection of a fuse is not always adequate! You should remove the fuse and check the continuity with a meter. Click here for more information on fuse testing.
  3. If a replacement fuse BLOWS when the equipment is turned on, troubleshoot the equipment for short circuits or overloads before again replacing the fuse. DO NOT continue to install higher and higher rated fuses until a smoke cloud indicates where the real problem might be!


 Connections:
Fact: All the electrical connections in the equipment provide an opportunity for intermittent operation; some more readily than others. Exposed metal surfaces provide an opportunity for oxidation and corrosion, and may result in intermittent or permanent electrical failure.

 Some common causes of these problems are:
A)  Salt air near coastal areas.
B)  Splashed liquids from "Road thaw" or "De-icing" chemicals.
C)  Some smogs in highly industrial areas.
D)  Corrosive fumes from leaking cooling units on refrigerators.
E)  Splashed contents of un-emptied "Drip cups" used in early Dometic® refrigerators.
F)  Hosing off the coach and having water mix with ordinary dust and dirt.
G)  No need to mention FLOOD water! etc...


Some connection failures can be caused by "pulling on the wire" to disconnect wires and cables. It's always best to grip the cable connector when disconnecting equipment. Keep in mind, you are sometimes dealing with "delicate" equipment, not battery cables.


 The world of circuit board testers!
  Fact: If a circuit board tester indicates the board is bad, the board is PROBABLY bad.
Another fact: If a circuit board tester indicates the board is good, the board MIGHT be good.

Circuit boards are forced to live in the real world. You do not know if the "complex" circuit board is going to work properly if it gets HOT or COLD or HUMID or MECHANICALLY FLEXED or has weird voltages applied to it.