Alternator Field 1 Circuit Breaker in climb

[M252]

Hi Mooniacs,

I was on a cross country flight across the Alps, yesterday, when ATC advised me to climb from FL100 to FL110. After I changed to climb settings suddenly the High Voltage indication illuminated. Later I noticed that the Alternator Field 1 Circuit Breaker had popped out. On the ground I measured the output of both alternators at 2000 RPM to be 28.6 Volts (clearly within where they should be: 28.6-28.8). When I switch both alternators off the battery voltage is about 26.3 Volt. I have a pretty new Concorde RG24-15.

When I pull the Alt. Field 1 Circuit Breaker the High Volt signal is on. This also happens when I switch off the right alternator. When I switch both on the High Volt illumination is off, same with only the right Alternator switch on.

- Are those High Voltage illuminations OK (ie. when Alternator Field 1 CB is pulled or right alternator off) or do they indicate a malfunction?

- Any idea what might cause the Circuit Breaker to pop out?

- I will have to fly several hours before I will get to a proper technician. Any issues?

Thanks for your advice...

-

[M252]

Mooney M20K 252 TSE, Serial 25-1223

[M252]

After almost 10 months the problem with my Alternator Field 1 circuit breaker occured again, yesterday, on a cross country flight: Shortly after take off I noticed that the High Voltage indication was on and the Alternator Field 1 circuit breaker was out. I recycled it a couple of times, however, it popped out again. My 252 has two alternators.

Has anybody experienced this?

Any idea what might be the cause?

[Marauder]

M - I have had a number of bad breakers over the years. I would see if the resistance of pulling the Alt Field 1 breaker feels the same as a a similar rated breaker. I have seen failing breakers not give me problem for months before they started popping more frequently. I can't advise on the correct illuminations. But I am sure my esteemed colleagues can... Sent using Tapatalk

[N201MKTurbo]

I would consider that your regulator is intermittent, or there is a short in your field circuit. Regulators can be NPN or PNP. A PNP regulator regulates the amount current being supplied to the alternator field. With a NPN battery power is supplied directly to the alternator and the regulator controls the field current by completing the ground side of the circuit. Most aircraft that I've worked on have the PNP type.

The reason I mention this is because your symptoms are indicative of the regulator failing constantly on which would give you the high voltage indication and the blown field breaker.

With an NPN regulator, it could be a short in the regulator wiring. With a PNP regulator it would have to be an internal short in the regulator.

[jackn]

FYI, in climb or cruise I see about 10 amps on each alternator. There is a service instruction si m20-78. Essentially it states to upgrade the VR-802 VRs to rev-c. This stops nuisance trips of the field breaker.

[M252]

Jack, are you saying that upgrade to revision C of my voltage regulator solves my issue?

"With an NPN regulator, it could be a short in the regulator wiring. With a PNP regulator it would have to be an internal short in the regulator. "

N201MK: how can I tell which type of regulator I have? Is there an easy way to determine where the short is?

[jackn]

No, first you would have to see which VRs you have. I had 2 VR-802. Later models came with 1 mooney p/n 800270-503. If you have the 802 then there should be a logbook entry satisfying the SI. Rev-c is stamped on the VR. When one of my VRs died, I found an inop 800270-503, had it repaired and replaced the 802.

First see how many amps your #1 is putting out. It shouldn't put out much more than #2 since #2 is the belt driven alt and therefore spins faster. If it does, the VR may need to be repaired.

[M252]

Thank you - I will take a look and will keep you posted.

[M252]

Hi, my Moooney is a 1990 252 and has a 800270-503 voltage regulator. When I tested it today the Alt Field 1 circuit breaker did not pop out. So my issue seems to be intermittent.

Have others seen this as well?

Does it indicate a faulty regulator or have others seen other causes, e.g. wiring?

I read in another thread that my voltage regulator can be repaired. Any recommendations?

[Tércio Rodrigues]

M252, I had some of the symptoms you mentioned in my 1989 M20J:

 

Volts warning flashing intermittently during warm up, climb, cruise or descent, in a few flights.

 

Then in one day, the CB of the Annunciator Panel had poped out, giving me the idea that the problem was in the Panel, not in the electrical system. Later that flight, we had a major short, with smell of acid of the battery in the cabin and smoke in the CB panel. I turned Master OFF, 7 CB (ADF, Radio Blower, COMM1 (this was the the one with GNS430), and the others I can't remember) had popped out, the result was landing after manually extending landing gear, no flaps, no radio, and all avionics and instrument cluster damaged.

 

We later discovered that the Main Battery CB positive touched the metal panel frame, making a short in the field. There was a small piece of rubber isolating the CB and the frame, but the vibration and friction damaged it.

 

I can't say yet if the problem I had was only related to the short in the battery CB, or if it had something else to do with the Volts Light flashing.

 

My plane should have a VR802, but I then find that it was replaced (don't know why) in the early 90s by a VR415F. Its a 28 Volts System, with only one Regulator, M20J Serial 24-3139.

 

Sorry about the english, I'm not native, so not familiarized with technical terms. Hope to help you to finding the problem!

[ArtVandelay]

I just had this happen to me (intermittent volts warning flashing, ammeter showing discharge), it fixed itself before I could do the alt field reset, this is on a 14v 201. This was on a second leg of a 7 hr trip.

Sent from my iPad using Tapatalk

[M252]

teejayevans and tercio, thanks for sharing your experiences... my issue occurs so rarely that it may or may not be diificult to find the root cause (I hope the latter....) I decided to remove the voltage regulator from the plane to get it checked. I sent it to Avionik Straubing in Germany. I will keep ypu posted.

[carusoam]

If English is your second language, Tércio. Your first language must be perfectly written!

I would not have known, if you didn't tell.

Thank you for sharing...

Best regards,

-a-

[M252]

My voltage regulator 800270-503 was checked by Avionik Straubing and they said it looks OK. They measure 28.7 V in both fields, which they say is a little high but acceptable. They recommended to switch the connectors in the plane to see whether the error (circuit breaker of alternator field 1 popping out) is caused by the VR or something in the field... So no progress really.

Has anyone observed intermittent problems in VRs that are difficult to measure (e.g. an electronic part that causes problems only at times?)

[ArtVandelay]

I just had this happen to me (intermittent volts warning flashing, ammeter showing discharge), it fixed itself before I could do the alt field reset, this is on a 14v 201. This was on a second leg of a 7 hr trip.

Starting to happen more frequently, pulling field CB resets it. Not really consistent, sometimes it works and sometimes it stops charging 3 times in 10 mins, there is probably a new VR in my future.

[carusoam]

Have you guys ruled out the CB itself?

Since they have the ability to wear out under constant load such as the headlight one.

Sorry if this has been covered already. Especially if I said so already...!

Good luck,

-a-

[ArtVandelay]

Have you guys ruled out the CB itself?

 

In my case, the CB is not tripping, I just use it to do a reset. So unless the CB is causing an open circuit, it's not the problem.  I could use some electronic cleaner on it, I will try that first, thx.

[M252]

T

Have you guys ruled out the CB itself?

Since they have the ability to wear out under constant load such as the headlight one.

Thanks, my shop mentioned that as well. They said that contact corrosion can result in increased resistance, which can cause the CB to get hot and trip (?). I will try contact cleaner as well. Not sure if that helps.