Alternator Help

sneedrv-6 · #1 03-01-2012, 07:49 PM

The same alternator has been on my plane since 1996. It is self exciting and only one wire from the ALT to a solenoid on the firewall and then to the cockpit. I always started the engine and then turned on the ALT. Recently when I would go to turn on the ALT I would get not positive charge, voltage increase or amp increase, but if I turned my alt switch on and off 5-20 times it would come online and work correctly. I figured it was the soleinoid on the firewall so I replaced that. I wanted to put a new ALT on the plane but could not figure out which ALT I actually have (prob a late 70's honda). I had the Alt completely rebuilt and a new voltage reg. installed. Went to fly with the new rebuilt ALT and had the same exact issue, would not come online, flip the switch a bunch of times and it would work.

I have since bench tested the old ALT at an ALT shop and was told the VR was dead. Although, if you touch the field wire to the battery it will come online and work correctly. After it is warm it seems to work also.

Currently, I have just about given up on the old ALT and have purchased a Samurai ALT.

My old mounting bracket will not work with the Samuria and I am wondering if someone could tell me where to get a bracket to mount the new ALT.

I see that Van's sells a bracket but according to this page it seems it will not work.

http://listerboy.com/alternator.htm

The plane is stuck in Utah and I have limited tools and definitely not much to fab a bracket myself. Any help would be great.

Jason Sneed
RV-6 (800 hrs)
O-360 with Airflow Injection

molson309 · #2 03-01-2012, 08:31 PM

Just a dumb question probably, but could it be that the switch is bad?

Ironflight · #3 03-01-2012, 08:36 PM

Hi Jason -

One of the things about the automotive alternators many of us use is that there are some differences in mounting ear dimensions that simply are accepted in the automotive installations that interfere with our Lycoming-mounted brackets. The bracket that Van sells now is adjustable - I have found that it can be made to work for at least the three different versions (of the "same" alternator) that I have run across.

Paul

mannanj · #4 03-01-2012, 08:48 PM

I used the regular Lycoming alternator mount that came with my engine with a small Nippon Denso alternator that the local starter/alternator repair shop said came from a Toyota fork lift.

Did have to slightly modify the starter/alternator "stay" bracket between the two to make it fit.

Just make sure that the ring gear and alternator pulley are on the same plane so that the belt runs true.

Might have to slightly bend the belt tightening adjustment bracket so that the bolt holes are "normal" to the attatch points.

ps. You don't turn the alternator "on" after you start your car engine; so why do it on your plane? Leave it on all the time.

AltonD · #5 03-01-2012, 09:07 PM

Quote:

Originally Posted by molson309

Just a dumb question probably, but could it be that the switch is bad?

I am with you. I was thinking the same thing.

sneedrv-6 · #6 03-02-2012, 07:44 AM

Thanks for the replies.. I forgot to mention I did swap out the ALT switch. (also tested it and it was fine) Last night I actually mounted the ALT using my old mount. It is not pretty, and I don't really want to leave it this way but the pulleys are in line. I spun the prop with the starter in the hangar and it seems ok. Going to taxi around today and see how it goes, once I pre-heat the engine.

Paul, long time no see... Can you give me the vans part number of the ALT mounting bracket from vans so I can order one. I have threaded holes in the bottom of my case for the mount, pretty sure this means I would use the Boss mounting bracket.

I am not the builder, and have some pretty odd things with my electrical system. The wire from my ALT goes directly to the shunt for the AFS EFIS, then it goes to the solinoid on the firewall (which my ALT switch activates) from there it goes to a newly discovered 35 amp circuit breaker that is actually mounted on the sub panel and can not be reached while in flight. I do not like this circuit breaker in this location, and I do not like the fact that it is 35 amp, while the new ALT is 55 or 60 amps. Other weird things is that I have an ALT field circuit breaker on the panel but I am not sure it is connected to anything, going to try and figure that out today. I do know that with the old ALT while it was working if I pulled the ALT field circuit breaker it did not take the ALT offline.

In my mind It seems fine to maybe get rid of the 35 amp sub panel circuit breaker, instead run the ALT wire to a 55 amp (maybe lower?) circuit breaker on the panel, and keep my solenoid setup on the firewall.

I forgot to mention, the way my new ALT is wired, the Field is just jumped to the BATT post. I know this is way different than everyone else but I do not see a problem with this setup. I could get more involved and wire it more like everyone else but I need a reason why. If I keep the current wire scheme I would just turn on the master and ALT switch before startup, shutdown I would pull the mixture and then turn off the master and ALT switch. I have read many posts here about not having ALT switches and just having a circuit breaker, for me I like having an ALT switch. If I get an audio alert from the EFIS about over voltage I just flip my large ALT switch right next to my master switch. In the -6 it is a little harder to see and reach the circuit breakers.

Thanks for the help! You guys are great

Jason

aerhed · #7 03-02-2012, 10:17 AM

I'd rewire the whole thing and follow someones decent schematic. The field wire on these isn't actually a field wire. It turns the regulator on and off. Also, I have no idea why your alternator output runs through a solenoid. Your big wire should just go through a protection device (breaker/ANL) and straight to buss. Also, the Denso alternators have a failure mode inside the regulator that can allow full field voltage when it goes. That's why I like a switch to control the "field" wire. Also, I like to mod the inside and hook the positive field brush parallel to the on/off wire. The field brushes get a full 12V applied normally and the field voltage is regulated on the ground side through the regulator. That way when you turn off the alternator you also remove power to the field brushes. That way, if the regulator goes internally you can remove field voltage completely. I still like being able to turn the dang thing off, no matter what anyone says.

krw5927 · #8 03-02-2012, 10:20 AM

Quote:

Originally Posted by sneedrv-6

Thanks for the replies.. I forgot to mention I did swap out the ALT switch. (also tested it and it was fine) Last night I actually mounted the ALT using my old mount. It is not pretty, and I don't really want to leave it this way but the pulleys are in line. I spun the prop with the starter in the hangar and it seems ok. Going to taxi around today and see how it goes, once I pre-heat the engine.

Paul, long time no see... Can you give me the vans part number of the ALT mounting bracket from vans so I can order one. I have threaded holes in the bottom of my case for the mount, pretty sure this means I would use the Boss mounting bracket.

I am not the builder, and have some pretty odd things with my electrical system. The wire from my ALT goes directly to the shunt for the AFS EFIS, then it goes to the solinoid on the firewall (which my ALT switch activates) from there it goes to a newly discovered 35 amp circuit breaker that is actually mounted on the sub panel and can not be reached while in flight. I do not like this circuit breaker in this location, and I do not like the fact that it is 35 amp, while the new ALT is 55 or 60 amps. Other weird things is that I have an ALT field circuit breaker on the panel but I am not sure it is connected to anything, going to try and figure that out today. I do know that with the old ALT while it was working if I pulled the ALT field circuit breaker it did not take the ALT offline.

In my mind It seems fine to maybe get rid of the 35 amp sub panel circuit breaker, instead run the ALT wire to a 55 amp (maybe lower?) circuit breaker on the panel, and keep my solenoid setup on the firewall.

I forgot to mention, the way my new ALT is wired, the Field is just jumped to the BATT post. I know this is way different than everyone else but I do not see a problem with this setup. I could get more involved and wire it more like everyone else but I need a reason why. If I keep the current wire scheme I would just turn on the master and ALT switch before startup, shutdown I would pull the mixture and then turn off the master and ALT switch. I have read many posts here about not having ALT switches and just having a circuit breaker, for me I like having an ALT switch. If I get an audio alert from the EFIS about over voltage I just flip my large ALT switch right next to my master switch. In the -6 it is a little harder to see and reach the circuit breakers.

Thanks for the help! You guys are great

Jason

Now you've got me thinking a bad solenoid could be why your alternator doesn't appear to come online. The switch on the panel activates the solenoid, but the solenoid doesn't close, so the output of your alternator is never connected to your electrical system. Could this be the culprit?

sneedrv-6 · #9 03-02-2012, 10:29 AM

I thought the same, fist thing I replaced was the solenoid as per first email. At this point I do not care much about the 1st ALT. Just going to throw it in the attic. I would like to know what the downside is if I run the new ALT through the solenoid. Seems like all everyone cares about is being able to disconnect the ALT if it fails or has an OV issue. The solenoid does this. Even if the Solenoid was stuck closed and would not disconnect the battery via the ALT switch I could just pull the breaker.

Thanks,

Jason

krw5927 · #10 03-02-2012, 11:02 AM

Sorry, I missed the part about the contactor in your first post. It almost sounds as if your system might be a good candidate for Bob Nuckolls' Figure Z-24 alternator overvoltage protection. It uses an alternator contactor with an additional overvoltage protection that would automatically trip the field (actually in your case solenoid activation) breaker in an OV event. B&C has the overvoltage modules at a pretty modest price.

http://www.aeroelectric.com/articles...r_Failures.pdf