Generator and voltage regulator

Rod Nowakowski · Post by **Rod Nowakowski** » Sun Jan 25, 2004 1:31 pm

I have a 1948 rag wing N4178V. The generator died and I had it rebuilt but on installtion, no power is generated. Fuse is good and all wires seem intact. Battery is new. Ammeter indicates discharge with a load but never goes positive. Generator/battery meter indicates battery ok but never indicates a charge being delivered even at 2,000 RPM. The rebuilder said it was "fried" and had slung metal internally. I also replaced voltage regulator which was worn but that was no help. Yes, I polarized the generator. My questions are: How do I verify that the generator can generate? How can I check voltage regulator? Any other ideas on what to check? Thanks, r

erjarv · Post by **erjarv** » Sun Jan 25, 2004 4:57 pm

A lot of folks think that to flash the field, a wire is placed momentarily between the field terminal and the battery terminal on the voltage regulator. Not so- flash it by touching the wire to the battery terminal and to the armature terminal. You may also want to check the ammeter for proper function. If that is OK, you can isolate the regulator by putting a jumper wire from the field post on the generator directly to ground and run the engine. Watch the ammeter for a positive charge, but dont run it for long as it may cause high rates of charge if the generator is working.

Doug Echelberger · Post by **Doug Echelberger** » Mon Jan 26, 2004 4:48 am

Rod,

I just went through this. If you "search" on Generator you witll get several posts on what to do to trouble shoot the Generator/Regulator. One thing I learned when doing the test to isolate the Voltage Regulator make sure all radios and lights etc. are turned off. Ane watch the amp meater no need to let it go too high. You just want to see if you are getting a charge.

Further, I have a good contact in Sacramento, (George's Electric) to check the Voltage Regulator if you find it suspect. I sent mine up and he checked it out for FREE if you can believe that, (found mine to be bad). You can also check out the Zeftronics web site for trouble shooting info. I am ordering the Zeftronics Regulator for my 35 amp. Generator, the guy at George's highly recommended the up grade. You will also find info on this in from the "search"

Hope this helps!

Doug Echelberger

Post by **GAHorn** » Tue Jan 27, 2004 6:21 pm

To check a generator with it removed from the aircraft, clamp it tightly by it's mounts or hold it firmly on the floor. With a jumper wire, ground the field terminal (the small terminal) to the generator case. Next clamp an automotive type starter-jumper cable whose opposite end is attached to a negative terminal of the battery to the case. Clamp another jumper cable to connect the armature terminal with the positive terminal of the battery.
A healty generator will spin like a motor. (And it will do so forcefully, so don't try to hold it in your hands without support or you may drop it and damage it. Put in on the floor and hold your foot on it.)
Search my other posts on this subject.

Romeo Tango · Post by **Romeo Tango** » Mon Feb 02, 2004 5:47 am

Rod, I am the custodian of N4179V, so we are closely related. One of my first and only mods was to replace the generator with an alternator. I like the notion of starting a dead system and charging (which a generator will do but an alternator will not), but I rather more like the more modern electrics and more stable power supply across RPM that is provided by the alternator. Not inexpensive, but good peace of mind and I'm very glad that I did it. There was nothing wrong with the generator, I just felt better with that change.

Richard

zero.one.victor · Post by **zero.one.victor** » Mon Feb 02, 2004 6:09 am

My ragwing has a 60-amp Cessna (Ford) alternator,added by a previous owner. It sure is heavy. I wonder what the weight is for this 60 amp alternator versus the 35 amp generator? Unless you spend a lot of time taxi'ing around with a big electrical load,I would think that a 35 amp generator would work fine. But then I haven't tried anything other than what I have.
I had a 1969 Cessna 150 before the 170,but don't recall if it had a generator or alternator.

Eric

Rod Nowakowski · Post by **Rod Nowakowski** » Mon Feb 02, 2004 1:16 pm

Thank you all for your replies. Here's the outcome. When the generator died, I had it rebuilt but still got no power. The shop that rebuilt it said they had tested it, as they did with all rebuilds, and it generated fine. I then replaced the voltage regulator, which was very worn, and still got no power. Hint - this voltage regulator was relatively new, but used, and was was said to be in perfect operational status when removed for upgrading to an alternator. Hmmmm. With some testing and the good advice of a friend and fellow 170 owner, I then replaced that voltage regulator with a guaranteed new one and all is back to normal. So.....there's some good advice in this story about used parts. No, I was not scammed. Like so many things in life, what some good folks believed, and what was true, just turned out to be different. Hope this helps some others. Rod N4178V

Post by **GAHorn** » Mon Feb 02, 2004 9:28 pm

At the risk of public roasting by a certain friend in Alaska....

If you wish to "troubleshoot" your generator system regulator and would rather not spend the enormous amount of money they get for an aircraft voltage regulator just for "testing" purposes...
...an automotive regulator from AutoZone (last priced below $30) will work just fine for the ground-test purpose.
Their PN VR-605 is a 20 Amp unit.
Their PN VR-699 is a 35 Amp unit.

Like all units, they will require "flashing" for polarity. The easiest method to "flash" polarity is to momentarily connect (merely touching momentarily works just fine) a jumper wire between the ARMature terminal and the BATtery regulator terminals after the battery master switch is ON but BEFORE starting the aircraft. This will polarize both regulator and generator.

Warning: Never use a regulator with amp value greater than the generator or you may overheat the generator. Use of a regulator with a lower amp rating than the generator is OK, but it will never ask the generator for max amperage capability. (It will only request it's own rated amperage.) Use of an automotive regulator will not harm an aircraft system but it is not FAA airworthy. I'm only offering this information for ground testing purposes.

N1478D · Post by **N1478D** » Tue Feb 03, 2004 4:04 am

The copyright is 1942, but Aircraft Electrical and Ignition Systems by G. B. Manly is a good resource. *

The International Cessna 170 Association