Home » GM 6.5 » GM/Detroit 6.5L – BATTERY CABLES


Excessive resistance caused by poor terminal con­nections and partial short circuits through worn cable insulation will result in an abnormal voltage drop in the starter cable. Low voltage at the starter will prevent normal starter operation and cause hard starting.

Whenever battery cables are replaced, always use a replacement cable that is the same type, diameter, and length. Some positive cables have additional feed wires attached to them and some negative cables have addi­tional ground leads attached.

Always be certain when replacing a battery cable to route it the same as the original cable.

NOTICE: When installing the positive battery cable to the starter solenoid, the inner nut on the solenoid battery terminal must be tightened before the battery cable and other leads are installed. Failure to do so may result in solenoid terminal and/or solenoid damage.

CAUTION: To prevent possible personal inju­ry from a moving vehicle or operating engine, do the following before performing the tests:
1. Engage the parking brakes and block the wheels.
2. Place the manual transmission in the neutral position or the automatic trans­mission in park.
3. On gas engines, disconnect the battery feed a t the distributor. On diesel engines, disconnect the battery feed at the engine shutoff (ESO) solenoid.

1. Test the voltage drop between ground (negative battery terminal) and the vehicle frame. Place one probe of J 39200 on the grounded battery post (not on the cable clamp) and the other on the frame.
Operate the starter and note the voltage reading.
2. Test the voltage drop between the positive battery terminal and starter terminal stud with the starter operating.
3. Test the voltage drop between the starter housing and the frame with the starter operating.
4. if the voltage drop in any of the above is more than 0.5 volt, there is excessive resistance in the circuit. To eliminate resistance, the cables should be dis­connected and connections cleaned. If cables are frayed or the clamps corroded, the cables should be replaced. When selecting new cables, be sure they are the same length and diameter as the ones being replaced. Battery cable routing is shown in figures 13 through 15.


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