How to know if alternator is charging?
08-16-2004, 06:30 PM
#11
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Thanks. Good idea.
I've done that tonight. To my surprise, the voltages look okay. About 13.9 Volts at jump start terminal (just a few feet from alternator) and 12.78 Volts at battery (beneath rear seat) when driving at say 2400 RPM. Channel 11 on climate control shows anywhere from a low of 10.8 Volts to say 12.4 Volts while driving. All with lights, AC, and radio on.
Surprisingly, replacing the alternator's voltage regulator / brush assembly just may have brought the alternator back to life. (The brushes on the old assembly looked fine.) Will do more testing this week.
Surprisingly, replacing the alternator's voltage regulator / brush assembly just may have brought the alternator back to life. (The brushes on the old assembly looked fine.) Will do more testing this week.
08-16-2004, 06:58 PM
#13
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Actually, both halves of the wave are rectified.
Just to pick a nit: A full-wave bridge rectifier (4 diodes per phase) just yields twice the voltage of a full-wave rectifier (2 diodes per phase). Both varieties rectify both halves of the AC wave and therefor yield an output with the same amount of ripple.
Each phase's winding would need to be center-tapped to provide current return for a full-wave rectifier. I'll have to check the Bentley schematic tomorrow to see if that's the case.
A half-wave rectifier, on the other hand, in the form of a single diode, rectifies only one half of the AC wave and therefor yields an output with more ripple.
Russ Bellew
Each phase's winding would need to be center-tapped to provide current return for a full-wave rectifier. I'll have to check the Bentley schematic tomorrow to see if that's the case.
A half-wave rectifier, on the other hand, in the form of a single diode, rectifies only one half of the AC wave and therefor yields an output with more ripple.
Russ Bellew
08-16-2004, 07:02 PM
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Re: Thanks. Good idea.
Numbers on channel 11 seem a little low to me. You should probably also check a splice of the battery cable in the passenger side footwell. It gets corroded with time and works as a heater => more resistivity and the voltage drop. Do a search on that in archives. I had to cut almost a foot of that corroded part of the cable. Only after that the charging problem disappeared. Since you've got 13.9 at the jump start teminal it means that the alternator is OK, but such a low readings at the "+" battery terminal most likely indicates this stupid design of the spliced battery cable. You can just pull the carpet at the pass side and you'll see what I'm talking about. Also, there is a pretty good article on that at sjm site - detailed r&r explanation.
HTH
Sergei Pokrovsky
'87 5KCSTQW, 187k miles
Anchorage, Alaska
HTH
Sergei Pokrovsky
'87 5KCSTQW, 187k miles
Anchorage, Alaska
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