Another Alternator Over Voltage failure

Must be contagious, seems like a lot of over voltage failures are occurring lately, could be the warmer weather I guess.

I had an over voltage condition this AM on my 6 year old Vans 40 amp regulator on my O-320 Lyc. I shut it down by removing the field voltage and flew back to home base. Once on the ground, I shut down the engine and then restarted in my normal start up procedure and everything appeared to be normal again, even flew around the pattern once. Rather than risk another episode with over voltage I thought I might as well have the alternator rebuilt or replaced since it is about 6 years old and has about 300 hours on it.

I?m looking to make this as painless as possible, financially and physically. Does anyone have auto part number replacements for the Vans 40 amp unit they were selling 6 or 7 years ago. I?m pretty sure it?s a Nippondenso type unit and has a built in regulator.

I?m hoping to be able to find a new or rebuilt unit I can easily swap in without having to change pulleys, wiring or mounting brackets. I?m not in a big rush so maybe just having my alternator rebuilt by a local shop might be an option, I haven?t checked with any shops yet since it is Sunday.

Any suggestions appreciated?. No I don?t want to upgrade to a Plane Power unit?.. yet.

647jc said:

Must be contagious, seems like a lot of over voltage failures are occurring lately, could be the warmer weather I guess.

I had an over voltage condition this AM on my 6 year old Vans 40 amp regulator on my O-320 Lyc. I shut it down by removing the field voltage and flew back to home base. Once on the ground, I shut down the engine and then restarted in my normal start up procedure and everything appeared to be normal again, even flew around the pattern once. Rather than risk another episode with over voltage I thought I might as well have the alternator rebuilt or replaced since it is about 6 years old and has about 300 hours on it.

I’m looking to make this as painless as possible, financially and physically. Does anyone have auto part number replacements for the Vans 40 amp unit they were selling 6 or 7 years ago. I’m pretty sure it’s a Nippondenso type unit and has a built in regulator.

I’m hoping to be able to find a new or rebuilt unit I can easily swap in without having to change pulleys, wiring or mounting brackets. I’m not in a big rush so maybe just having my alternator rebuilt by a local shop might be an option, I haven’t checked with any shops yet since it is Sunday.

Any suggestions appreciated…. No I don’t want to upgrade to a Plane Power unit….. yet.

Click to expand...

Joe, if you have the Vans 35a alternator it is commonly available at auto parts stores as a 14184. Or, ask for:

1978 Honda Civic, CVCC, no air conditioning

It will come with a fan that blows the "wrong" way, but you can leave it in place, it is fine as is.

If you need a regulator, it is a 1975 Ford LTD unit, VR166 being a common number.

This topic has been discussed many times on the forum, the search engine can pull up the old threads.

Samurai

Joe,

If it is the Denso unit with the built in regulator, I think it might be the unit from the 87 Suzuki Samurai. Lester #14684. 60 Amps, internally regulated.

If it is externally regulated, it is as Sam mentions above.

Thanks Sam & Pete,

My mistake, I've been thinking my alternator was a 40 amp unit and I just looked at my FWF kit documentation and it listed the unit as 60 amps.

I had searched through the forum and all I could find was info on 35 and 60 amp units which mine was neither. Anyway, mine is the 60 amp, Vans number 'ES 14684' unit so I think I can dig out the correct auto part numbers now. I'll look into the Lester #14684 you provided Pete, same number as Vans ES number.

Thanks Again guys.

Well DARN!

I replaced my alternator last week to correct my over voltage problem and everything appeared OK but about an hour later I got another over voltage alarm, same as before the voltage jumped up to 16.5 volts. I took the alternator off line via my field switch and flew home on battery.

I tried switching on the field again once on the ground and the alternator would not come back online, voltage stayed low and no charging indication.

Now for the difficult part, I have an EXP BUS II unit installed for all of my power switching. It has worked fine for 6 years but I have always dreaded the day when it developed problems and I think it may be the culprit now. The EXP uses PFs (Polyfuses) which open when excessive current flows and later will reset automatically when the load is removed.

I?m not very knowledgeable how the alternator and inbuilt VR works but I suspect the single field enable wire is also a sense signal that the VR uses to determine how much voltage to provide to the battery or power bus. I?m wondering if maybe the PF gets warm and then develops a small resistance which may cause the voltage on the sense or field line to go down which would cause the VR to output more voltage than the nominal 14.5 volts. Does that sound possible?

The EXP has several switches, circuits, each with its own PF so I think I may disconnect my landing light circuit and use that switch / PF to supply the alternator field / sense feed. That should eliminate the EXP alternator circuit in case it is the culprit.

Also, the EXP has a built in OV protect circuit that will shut down the alternator field automatically if it senses an OV. I think that may have also tripped this last time preventing the EXP from turning the alternator back on. If the EXP does detect an OV and shuts down the alternator circuit, you must disconnect the airplanes main battery to clear the OV condition or you can install a separate switch to reset the condition in the EXP which I have not done, was not aware of the switch option.

I used to live out in Saylorville and whenever I had issues with "unique" electical systems, I would only go to Ankeny Auto Electric. They have rebuilt 3 alternators for me in the past and they are very knowledgeable. You should give them a buzz. They were by the John Deere plant on Ordinance RD the last time I remember.

You might consider modifying your 60 amp ND alternator to make it externally regulated and use a Ford-type external regulator with it. My personal opinion is that the internal regulator in these is somewhat fragile and if you turn the field on and off while the engine is running, you can risk blowing up the internal regulator... seen a few failures on them that seems to lead to that conclusion, especially since the folks who just leave the field breaker/switch on all the time seem to not suffer such failures.

I've got the EXP Bus in my plane too.... not my choice and I'm not a big fan of the EXP Bus, but it was in the plane from the original builder, and I'm not a huge fan of the polyfuse concept either. I suspect one of my 3 amp polyfuses on my avionics section has an excessive voltage drop so it's possibly you may be seeing a similar condition on your alt field circuit polyfuse as you suspect. Trying one of the other polyfuse circuits as you surmise might very well be a valid test. I'm using my "suspect" polyfuse to power the intercom, so even with a slight voltage drop, it still works OK for that usage.

My plane does have a separate solenoid-style master relay so I can reset the whole thing in case of a suspected OV trip, at the flick of my master switch... if your plane does not have a separate master relay and instead only uses the EXP Bus's "pseudo master relay", then yeah you probably do have to unhook the battery to reset it when the OV circuit trips.

Thanks for the input Neal. I was so frustrated when the over voltage occurred with the new alternator that I didn't try shutting everything down and restarting to see if the alternator came back online so I may in fact be able to reset the over voltage protect circuit simply by shutting off the master. The documentation says you must disconnect the battery or use the optional switch (not installed) and I assumed the always present voltage through my firewall mounted master relay coil was enough to keep the OV logic in a tripped state.

My last alternator lasted over 6 years with no problems assuming it is still OK which I think it is because the exact same over voltage condition occurred with the new alternator also after about one hour of use.

I think I will go ahead using a different EXP BUS circuit for the alternator field and if that works, I will probably replace the EXP BUS unit with a similar footprint assembly using CB switches. That way I won't have to redesign my panel and wont have to do any rewiring other than disconnecting and reconnecting all the push-on connectors.

Just wanted to update this thread with what I think was the original problem and what the final solution or fix was.

After the second alternator failed with an over voltage alarm and then would not come back online, I took the cowl off and discovered the plastic field electrical plug that snaps into the back of the alternator was not fully seated and locked into place. I suspect this is what caused the new alternator to not come back online after the over voltage alarm. To correct, I pushed the plug fully into the alternator and made sure the locking clip had engaged.

I also have a single conductor Molex connector about 6” back from the plastic plug that connects the original field plug pigtail to my tefzel wiring. That connector was also loose and partially disconnected. I took the connector apart, pinched the female conductor a bit and reconnected the connector. I then also used some electrical tape to insure the connector stayed fully connected.

I’ve since flown about 3 hours and have not had any more over voltage alarms or has the alternator gone offline. So, I think the original over voltage problem with my first alternator was caused by the loose Molex connector. The second over voltage alarm with the new alternator and then the alternator not coming back on line was probably due to the plastic plug not seated.

From what I observed, it appears a loose or intermittent field connection can cause an over voltage condition, at least it did on my airplane with two different alternators. I probably should have gone through the wiring more closely after the first over voltage alarm rather than ordering a new alternator but I guess now I have a good spare alternator (the original unit). Anyway, the new alternator cost me $98 from Amazon and it was not a difficult replacement so I don’t feel too bad.

I had the exact same issue, with the same set-up as you ? internally regulated alternator running through an ex-bus. I went through the same troubleshooting process, changed the alternator, bypassed the ex-bus OV circut, etc. I too found the culprit to be a loose plug connection on the alternator. It was hard to find because every time I pulled the cowl I would re-seat the plug as a matter of course. It made it appear as an intermittent problem. It does not need to be overly loose to cause the issue.