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Don’t forget, with main switch off, to check resistance from field wire to ground. It should not be 0 ohms.
It may not show infinite however as other devices on the unpowered bus may have resistance to ground. For example any radio or device which comes on when the main sw is activated. A couple hundred ohms would be common.
An ok Continuity check of a wire end to end does not preclude the wire also being grounded
On Jul 30, 2019, at 7:37 PM, Corbin Geiser c_geiser@...
I’m starting to think I need a new alternator. Wiring seems fine to me. Continuity checks are good.
I have seen frayed wires cause similar problems
Just an update on the alternator field issue. I replaced the 5 amp breaker but that didn't fix it. My buddy that has a PP voltage regulator had the 28 volt version and not the 14 volt.
I am going to pull the engine off again this afternoon and run a wire from the Field term, on back of Alternator, to the back of the 5 amp breaker. If it doesn't pop then I guess the problem is between breaker, voltage regulator, and firewall.
Thanks! I plan on doing this tomorrow. I found a buddy that has a new PP voltage regulator and some 5 amp breakers.
I’ll replace the breaker and if that doesn’t stop it from popping then I’ll swap the voltage regulator.
I often take it on the master solenoid or on the panel cig lighter... If those are inconvenient try the battery + post as long as the master switch is on
This sounds easy to test.....where on bus should I test voltage from? I am not familiar with working with the bus. Do I just place the probe anywhere on a good contact along bus?
The easiest test for a functioning alternator is to read the voltage on the 12V bus. The battery without alternator will be 12.6 volts or less. A functioning alternator will show more than 12.6 volts. Normally the voltage regulator will adjust the field current to produce 13.8v with an automotive regulator and possibly as high as 14.4v with an aircraft regulator.
The engine must be running for the alternator to produce power, and may not produce full power at less than about 1600 RPMs.
50 amp breaker is handling the current out from the alternator. It is only active when the alternator is spinning otherwise current from the alternator is zero. Battery charge plus electric items is probably 35 amps right after takeoff. If engine is not turning or field voltage is zero, then all current is coming from the battery.
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"Corbin Geiser c_geiser@... [Q-LIST]" <Q-LIST@...> wrote:
Update: I’ve located a 50amp breaker labeled MAIN. I turned on Master, electronics come on, and then I pulled the 50amp breaker. Nothing turned off. I’ve removed the breaker and would like to know how to test to confirm if it’s working or not.
Should all electronics turn off if I pulled the MAIN breaker?
An open alternator output, for example 50a breaker tripped or disconnected wire could cause the field breaker to blow only if the regulator suppling full voltage to the field draws enough current to trip the 5a field breaker. This should not be possible but if the 5a breaker is old and tired and, say, tripping at 3a your could see it trip. I have never seen this happen though.
Don’t overlook wire fault as a cause, insulation worn through and he wire touching something grounded etc.
Ok, great news.
Now disconnect the Field wire from the back of the alternator and leave hanging.
Does the 5A break still blow? If it does it's a bad regulator. If it doesn't blow now, then we may have a shorted field in the alternator.