Preliminary Electrical Checks

Read all these paragraphs very carefully! The picture below represents a common area of truck electrical problems. The starter picture is concerned with the heavy cables which connect the battery to the starter and also connect the battery to all other electrical circuits on the truck. In this picture, those cables are sheathed in the light grey cable guards. All truck electrical supply current passes through these heavy cables, and a loose or oxidized connection can cause very unusual electrical problems throughout the truck.

You may have noticed some nasty looking goop on these connectors on the new trucks. This is an attempt to prevent oxidation by sealing out harmful moisture and salt spray. While driving on winter roads, the salt spray under your hood creates a very hostile environment for your electrical cables and connectors.

When you are experiencing weird electrical problems or engine power loss on E-engines (E-engines is trucker slang for electronic or computer controlled diesel engines), you had better check these cables for tightness! The loose or oxidized connection forms a high resistance, and the E-engine computer starts doing strange things because of this high resistance. In fact, it has been suggested that more than 90% of todays E-engine problems are due to high resistance problems with the computer power source or the engine sensors.

Before working on any of these cables, disconnect the battery ground cable (the black one) from the batteries. Failure to disconnect the batteries before tightening these connectors, could result in personal burns, eye injury, damaged parts, and damaged tools. If you don't know how to disconnect the batteries, refer the job to a professional. Try to rotate the cables around the lug, using a non-metallic object for leverage. If you can move the connector (cable flexing does not count), it needs tightening. Sometimes, oxidation of the connection will cause problems, even when the connection is physically tight. This is especially true of battery post connections. The fix for invisible oxidation problems, is to first slightly loosen the connection, then rotate the connection, feeling the physical friction of movement. This will rub off any oxidation, and form new non-oxidized electrical surfaces. This method may work for battery posts, but the recommended procedure for battery connectors is to completely remove the connector and clean the battery post and the inside of the connector. Now, retighten the connector and then reconnect the batteries.

Loose or oxidized battery cable connections normally cause start up problems, but it never hurts to check these connections as part of your preliminary checks.

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