hi folks, not posting a question but a little write up on my findings fixing a 0 Amps situation I had during flight. As I was Dr Googling it there were so many different approaches and so many different outcomes I thought it might be helpful to summarize the troubleshooting steps I took and how to diagnose the problem.
Right after annual on her 2nd flight only, in the midst of cruise the Aspen PFD reported it was running on battery. I checked the JPI and it read 0 amps on the ammeter. Yikes. So while now with only 30 mins to spare, I took the checklist out and tried to cycle the alternator switch of the master, no dice. Tried it a number of times. Only one time it reported 5 Amps, dropping down to 0 shortly after. Running the checklist I found critical as I lowered the gear (electric driven) so I was good to go for a landing.
While this seems like a hard alternator failure at first and what many would perceive rightfully so, took the cowling off and checked the following:
- bus voltage on the alternator
- no ground leak (eg chassis of alternator negative and check voltage between chassis of alternator and another ground point of the airframe).
- with master and alternator on check magnetic field on the pully to see if a screw driver would hold.
- physical inspection of the coil, is it clean, is there oil over it?
This seemed all fine. If one of those is not correct, it is likely a alternator failure. But in my case it was not. I almost jumped the gun and ordered a new alternator but glad I didnt. If btw you are looking for a new alternator I would recommend the plainpower one that comes with a conversion kit that fits nearly any engine with little customization.
Next to check is the "Field Voltage". This is a low current steering for the alternator. In fact the alternator portion of the master switch provides the bus voltage through the voltage regulator (and over voltage relais) through a circuit breaker to the field terminal of the alternator basically regulating the voltage output of the alternator.
In my case at the alternator terminal it reported 200mV. Not good. But this still can mean many things as there are some components in between. Many have reported faulty wiring or a break in the wiring. Since the annual just happened and many hoses were replaced, I was worried that the cable might have snapped or so. But then, it was running fine, and then busted. So wiggling wires is a good step to see if the voltage over the field might change.
Didn't do much for me.
Slowly tracing it back through the circuit breaker, which is also a somewhat known issue that the breaker may have some corrosion or resistance causing the Field to drop. But not to 200mV. Still checked, was fine.
In the PA28R that I have the original part of the electrical system provide for a separate voltage regulator and over voltage relais. Checking the relais/solenoid to make sure this is was not stuck in a certain way. Here too, if it was busted it should not report 200mV but hard 0.
The interesting thing was during this phase of troubleshooting, suddenly the voltage of the Field started to jump all over the place (still measured at the alternator terminal). 1-5-9-6-2-11 and so on.
That condition made the regulator very suspicious and like said both the regulator and solenoid were original. We ordered a R1224(-12 for 12V and -24 for 24V) (planepower model now hartzell) as a replacement that has an over voltage protection built in, including an alarm terminal. Note that the replacement is straight forward but not, as the terminals on this one require new ring crimp terminals on the wires and some possible extensions but that is minor.
After this replacement the voltage was steady and very good to go. All in all it was about $400 for the regulator and 3 hours of AP time.
I wanted to write this down to share since I read some messages of certain "troubleshooting" methods include rip and replace. Like how I almost fell in the trap of replacing the alternator since that is most suspect or common. I am glad I went through the extra steps.
One thing that I forgot to mention is that the Field voltage issue can also be caused by bad brushes on the alternator. This could be true IF the field voltage is accurately measured at the field terminal, but the alternator is not getting energized at all (won't be magnetic at the pully).
I was advised however that IF the brushes were the issue and the alternator is old-ish, that it is more cost effective to replace it with a new alternator as the labor to fix that may not weigh up against a new alternator and then better to have a new one. Because I am telling you, it being my first in flight emergency it is stressful enough and i rather not worry when the next time this things may feel, so it is probably an extra buck for the peace of mind.
Thank goodness for training and checklists.
Attaching a diagram (from a PA28R) where you can see the Bus voltage through a 5A CB going to the alternator portion of the master switch, through the over voltage solenoid, into the regulator to the field terminal of the alternator.
The alternator bus terminal going through a 60A and ammeter shunt to the master solenoid.
The master switch energizes the coil of the solenoid to link the battery to the electrical system and energizing the positive portion of the coil (not the alternator). The alternator would provide power to the electrical system regardless of master switch, but alternator on (field voltage) if it were rotating.
One other thing to note is this:
If you're close to regulated airspace, do make a call that you have a possible alternator issue. Not callign an emergency, but if your master and alternator are a single switch (but dual pole), you need to cycle your whole master whcih will drop all electronics (radio, nav etc). this way ATC knows you are troubleshooting in case they want to get hold of you.
ATC in my case was, as always, very helpful, asked if I wanted to land at their airfield but I felt I could make it back to my home base, he had informed my home base and it was very nicely facilitated. No paperwork necessary since there wasnt an emergency (yet), but the added assistance makes it easier to deal with.
Right after annual on her 2nd flight only, in the midst of cruise the Aspen PFD reported it was running on battery. I checked the JPI and it read 0 amps on the ammeter. Yikes. So while now with only 30 mins to spare, I took the checklist out and tried to cycle the alternator switch of the master, no dice. Tried it a number of times. Only one time it reported 5 Amps, dropping down to 0 shortly after. Running the checklist I found critical as I lowered the gear (electric driven) so I was good to go for a landing.
While this seems like a hard alternator failure at first and what many would perceive rightfully so, took the cowling off and checked the following:
- bus voltage on the alternator
- no ground leak (eg chassis of alternator negative and check voltage between chassis of alternator and another ground point of the airframe).
- with master and alternator on check magnetic field on the pully to see if a screw driver would hold.
- physical inspection of the coil, is it clean, is there oil over it?
This seemed all fine. If one of those is not correct, it is likely a alternator failure. But in my case it was not. I almost jumped the gun and ordered a new alternator but glad I didnt. If btw you are looking for a new alternator I would recommend the plainpower one that comes with a conversion kit that fits nearly any engine with little customization.
Next to check is the "Field Voltage". This is a low current steering for the alternator. In fact the alternator portion of the master switch provides the bus voltage through the voltage regulator (and over voltage relais) through a circuit breaker to the field terminal of the alternator basically regulating the voltage output of the alternator.
In my case at the alternator terminal it reported 200mV. Not good. But this still can mean many things as there are some components in between. Many have reported faulty wiring or a break in the wiring. Since the annual just happened and many hoses were replaced, I was worried that the cable might have snapped or so. But then, it was running fine, and then busted. So wiggling wires is a good step to see if the voltage over the field might change.
Didn't do much for me.
Slowly tracing it back through the circuit breaker, which is also a somewhat known issue that the breaker may have some corrosion or resistance causing the Field to drop. But not to 200mV. Still checked, was fine.
In the PA28R that I have the original part of the electrical system provide for a separate voltage regulator and over voltage relais. Checking the relais/solenoid to make sure this is was not stuck in a certain way. Here too, if it was busted it should not report 200mV but hard 0.
The interesting thing was during this phase of troubleshooting, suddenly the voltage of the Field started to jump all over the place (still measured at the alternator terminal). 1-5-9-6-2-11 and so on.
That condition made the regulator very suspicious and like said both the regulator and solenoid were original. We ordered a R1224(-12 for 12V and -24 for 24V) (planepower model now hartzell) as a replacement that has an over voltage protection built in, including an alarm terminal. Note that the replacement is straight forward but not, as the terminals on this one require new ring crimp terminals on the wires and some possible extensions but that is minor.
After this replacement the voltage was steady and very good to go. All in all it was about $400 for the regulator and 3 hours of AP time.
I wanted to write this down to share since I read some messages of certain "troubleshooting" methods include rip and replace. Like how I almost fell in the trap of replacing the alternator since that is most suspect or common. I am glad I went through the extra steps.
One thing that I forgot to mention is that the Field voltage issue can also be caused by bad brushes on the alternator. This could be true IF the field voltage is accurately measured at the field terminal, but the alternator is not getting energized at all (won't be magnetic at the pully).
I was advised however that IF the brushes were the issue and the alternator is old-ish, that it is more cost effective to replace it with a new alternator as the labor to fix that may not weigh up against a new alternator and then better to have a new one. Because I am telling you, it being my first in flight emergency it is stressful enough and i rather not worry when the next time this things may feel, so it is probably an extra buck for the peace of mind.
Thank goodness for training and checklists.
Attaching a diagram (from a PA28R) where you can see the Bus voltage through a 5A CB going to the alternator portion of the master switch, through the over voltage solenoid, into the regulator to the field terminal of the alternator.
The alternator bus terminal going through a 60A and ammeter shunt to the master solenoid.
The master switch energizes the coil of the solenoid to link the battery to the electrical system and energizing the positive portion of the coil (not the alternator). The alternator would provide power to the electrical system regardless of master switch, but alternator on (field voltage) if it were rotating.
One other thing to note is this:
If you're close to regulated airspace, do make a call that you have a possible alternator issue. Not callign an emergency, but if your master and alternator are a single switch (but dual pole), you need to cycle your whole master whcih will drop all electronics (radio, nav etc). this way ATC knows you are troubleshooting in case they want to get hold of you.
ATC in my case was, as always, very helpful, asked if I wanted to land at their airfield but I felt I could make it back to my home base, he had informed my home base and it was very nicely facilitated. No paperwork necessary since there wasnt an emergency (yet), but the added assistance makes it easier to deal with.
yeah great addition forgot to mention the brushes test with resistance check while field wire is disconnected!