[gwagen]

Hi Guys!

Not sure what the issue is, alternator has been replaced as well as the battery.

Will only charge intermittently with little electrical load, switch on the a/c or raise the header. Low voltage alarms, gauge drops to 10-11 volts and stays there.

Will sometimes at random start charging again, usually not though.

Not sure what other components could be causing the issue.

The previous alternator behaved the same way, the repair shop tested it and said it was toasted, not sure if I believe him though as he was keen to sell me a new one.

Grounds are in good condition, help please!

Thanks!

P.S. Its a diesel

 

[rickfly]

how is the wiring going to the battery or starter? i have seen resistance build to the point of being unable to charge the batteries. check the voltage at the battery, then at the terminal on the alternator,with the engine stopped is there a difference? ohm out the wiring from the alternator hot wire to the connections and the battery. is your key switch failing to supply a signal to the alternator? i have seen them fail also. simply put a charging system has to have a signal to energize the field that come from the key, if it is not there or intermittent, then the system cannot work, if the resistance in the wires is high it generates heat instead of charging the battery. connections may look good, but must be cleaned thoroughly with scotchbrite pad and even put a little antiseize on them. the regulator is usually built in or piggybacked on the alternator, its job is to see the voltage from the battery, then supply more or less voltage to the field circuit of the alternator, which then sill deliver more or less output... there are some single wire alternators also, and they have a continuous draw from the battery, but have a kind of sleep mode that when the alternator reaches a minimum speed they wake up and the internal regulator adds current to the field and output increases..

 

[gwagen]

You've given me an idea, the instrument panel near the ignition switch gets very hot when running, probably some wires chewed/rubbed through and creating that resistance?

Sound plausible? I will clean and tighten every connection I can and see if that does it.

What is an acceptable number for resistance?

Many thanks!

 

[rickfly]

virtually 0 is the best number, but a few ohms is acceptable, resistance is heat just like your toaster element..