IML: Elusive electrical gremlins

[Joe Strickland <jwstrick426@xxxxxxxxxxxx>]

One helpful way to look for electrical connection problems is to turn on the device (load, such as AC fan, radio, wipers etc.) for a few minutes without having the engine running.  Then turn the item off and feel along the wiring (if possible) searching for a hot spot.  Bad splices can be found this way sometimes.  Also look for discolored wire insulation or evidence of charring.  Bad connections cause heat to be generated at that spot.  Corrosion of contacts in connectors is often a cause of heat and further deterioration.  Contacts should be bright and shiny, not dull, gray or green.  Any connector that has moisture get in it is likely to corrode and increase resistance to current flow and then the connection heats up.  It is possible for a bad connection to start an electrical fire if things get too far advanced.  This is more likely with loads that supply or draw heavy current, such as the generator/alternator, heater/AC fans, power seats and windows etc.

If splices are suspected and can't be located easily by feel, it is possible an infrared camera might help find the bad spot.  Connections to/from ammeters in instrument clusters are known problem areas.  Make sure that all hardware that fastens the leads to the ammeter are bright and clean.  Of course, before removing any electrical items under the dash or probing with hands or meter leads, make sure you disconnect the battery!  Not all surface ammeter hardware is all that needs to be inspected.  Sometimes additional hardware underneath the surface hardware has corrosion or discoloration due to bad/loose connections that will not be seen until the ammeter is completely removed from the instrument cluster.

A word of caution about ammeters:  There is a shunt associated with an ammeter so that the meter movement actually only carries a very tiny amount of current to indicate charge/discharge conditions.  The shunt can appear as a large wire or metal strap.  If you disassemble the ammeter from the instrument cluster, be sure to observe every part that comes off and assure that all go back together just as they were originally!  The actual meter movement will vaporize in a split second if it has to try to pass all the current that the shunt does!

Large wires which pass through a bulkhead connector are often trouble spots.  The heavy current tends to make things heat up if any corrosion is present and then the insulation of the connector and wire can even get discolored and charred.  Always look for any evidence of this type when chasing these electrical gremlins.

More recent year production started applying some clear silicone grease to connector contacts to help keep out moisture and oxygen.

Joseph W. Strickland
1021 Vaughan Lane
Tioga, TX 76271-2937

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