Voltmeter drop when warm

Anyone having issues with the voltmeter dropping to 12 volts or less after the engine is warm (10 to 20 minutes was the normal amount of time for me) check the cable on the positive battery terminal to the fuse panel. It’s the small wire. Mine was corroded inside the terminal lug. After replacing the lug and cutting back the wire to a clean area I now have 14 volts all the time. I ordered the 2 AGW lugs from amazon and some crimp sleeves as the 2 AGW were a bit too large. A crimp tool is a must


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Thanks for sharing this information Pete. I am sure that this would leave many people scratching their heads.

Thanks Joe. I’ve been chasing this for a while. Thought I had it with new battery cables but it only improved it a bit. With the new lug and removing the bit of corroded wire the problem is solved and my dim dash light issue is gone also. I have read that the 120 amp fuse could cause the problem too as they get older. I’m not sure how but people have switched them out and cured the problem. I’ll replace the wire at a later date.

Any electrical wire or component that is under load will get warm or hot. This is especially noticeable around the connectors because this is the weakest point of the circuit due to the crimping of the cable. The heat causes the structure of the copper cable to break down which in turn creates a resistance in the cable which then causes more heat and thus creates more breakdown and more resistance. So the cycle continues until the resistance prevents the full voltage or current from being maintained and you get a low voltage reading.
When ever you are chasing electrical faults, it is always worth looking for any warming around connectors as this may give a clue to the location of the fault. You can usually cut the cable back an inch and fit new connectors but cable replacement is a better option if possible.