Friday, December 09, 2005

Alternator Contd. Contd.

According to the 740 manual I have, a voltage drop at the battery(measure voltage across battery with no load and with load - headlights, rear defrogger, blower fan on high- and compare) should be no more than 0.7 V. My measurements were 14.2V with no load and 13.3V with the above accessories on, for a voltage drop of 0.9V. I was concerned, but my friend Stew said that this was completely normal given the temperature (8F) and my 55A alternator.

Next I checked for voltage drop in both the power circuit (measure voltage between alternator + and battery + with load/no load and compare) and the ground circuit (measure voltage between alternator ground and battery - with load/no load and compare) I found a voltage drop in the ground circuit that was slightly more than the allowable 0.4V

I was lazy and just ran a redundant ground from the alternator housing directly to the negative battery cable.

The charge light was still on! Stew suggested we unplug the spade connector at the back of the alternator (red wire) and if the charge light went off the alternator was a bad unit. It went out. BAD rebuilt Bosch alternator :( I'm glad that I'm working on a Volvo where the alternator is easily accessible!


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