Delco Generator

David Laseter · Post by **David Laseter** » Mon Dec 30, 2002 2:35 pm

We tried that used generator and it isn't working either. I'm guessing that it was going bad and caused the previous owner to think he needed to go alternator. Anyway, George thanks for the reminder about Aerotech stated in the previous post above. I'll give them a call and maybe get a new one. The ONLY thing that I believe for sure is that my generator's armature was bad. This is what the electrical shop told me. The mechanics are troubleshooting the best they know how.

Post by **GAHorn** » Tue Dec 31, 2002 5:05 am

A simple test of a generator on the workbench is to ground the field terminal (the small one) to the gen case, and using battery jumper cables, connect a negative battery terminal to the gen case. Clamp the positive battery terminal to the Armature terminal (the larger one). A good generator will thusly be turned into a DC motor and will spin away.
It's always a good idea to first inspect the brushes by looking beneath the brush cover first to determine they are in good condition and the brush leads aren't damaged or obviously shorted. (It'd be a shame to use battery cables and a battery to weld them to the case!) But, if things are OK, then the gen will simply spin up properly. Hold onto the gen securely because it can torque out of your hands as it initially spins up. (In fact, doing this little trick for an hour or so is a common way to seat new brushes to the commutator.)

zero.one.victor · Post by **zero.one.victor** » Tue Dec 31, 2002 6:41 am

Neat trick,George! Hadn't heard of that one. Is there an easy way to test a regulator for proper operation,perhaps with a battery and voltmeter/ampmeter?

Eric

Post by **GAHorn** » Tue Dec 31, 2002 7:48 am

Well, yes, actually. In fact, most regulator problems (and some generator problems) can be troubleshot with only a jumper wire with alligator clips.
If you clip one end of the wire to the Fld terminal of the regulator and the other to ground you should see a charge occur. This basically takes the regulator out of the circuit and if no charge occurs, then the gen is the likely culprit. However, if the charge rate increases/decreases with engine speed with this setup, then the regulator is at fault.
In the above example if you got no charge, then clip one end of the jumper wire to the regulator Arm terminal and the other end to the Bat terminal and if you then get a charge, you've confirmed that the regulator is at fault.
There are some other simple checks you can perform on a regulator prepatory to making repairs on it, but few of us are equipped with the necessary parts. Example: Build yourself a continuity test-light using two jumper wires with a cabin dome-lamp or No. 87 bulb in the middle. (If you connect one wire to positive batt term, and the other to the neg term, the lamp will light.) Now, by connecting one end to the Batt term of the regulator and the other end to either battery terminal....and using the plain jumper wire mentioned earlier in this message to connect the ARm terminal of the reg to the other battery terminal,....then the lamp should NOT light indicating that the regulator is not shorted. But with the reg cover removed and using finger pressure to close the contacts on the Batt term coil, then the lamp should light. This proves the regulator's circuit breaker is OK.
Moving the test-lamp connection from the reglulator Bat term to the base (case) of the regulator should make the center (Arm terminal) contacts move. If they don't, ...throw the regulator away. Moving the lamp connection from the ARM terminal to the FLD terminal on the regulator should illuminate the lamp. Lifting the contacts at the FLD term coil should extinguish the lamp. Release them, (the lamp lights again) and then by closing the Arm contacts, the lamp should either dim or go out again. If these tests don't work, then the regulator is internally shorted.
None of these tests help you adjust the regulator though. You need a test bench with proper equipment to do that.

wa4jr · Post by **wa4jr** » Thu Jan 02, 2003 1:57 am

George, one of your posts here rekindled a question I have often wondered. Since a generator is just a motor in reverse, so to speak, would it not have been possible to have one unit do two tasks on the O-300? A starter/generator as is common on turboprop aircraft. Once the start is finished, the starter motor then becomes a generator...saving weight and space. Comments?

David Laseter · Post by **David Laseter** » Thu Jan 02, 2003 4:43 pm

Good morning David, the part number of the delco generator you need should be a 1101898 12v-35a gear driven. I have these in stock and your cost would be $182.50 exchange with a $200.00 deposit. We accept mc, visa, discover for payment or you can ship yours to us first and you wouldn't have the core deposit.
I would suggest if you were going to order to call us at 800 634-0190.
Thanks, Mike Evans, Aerotech of Louisville

Post by **GAHorn** » Thu Jan 02, 2003 8:38 pm

wa4jr wrote:George, one of your posts here rekindled a question I have often wondered. Since a generator is just a motor in reverse, so to speak, would it not have been possible to have one unit do two tasks on the O-300? A starter/generator as is common on turboprop aircraft. Once the start is finished, the starter motor then becomes a generator...saving weight and space. Comments?

There are two major differences in the starting rotation of recip vs turbine engines. 1. The recip engine doesn't need high speed of rotation but the turbine does. 2. The turbine doesn't need high torque to begin rotation but the recip does.
A recip engine can be started with low speed rotation but since it needs high torque at that low speed to overcome compression resistance, it needs a motor capable of providing that high torque. There are two ways to do that. A very heavy, large motor supplied by a very large, heavy battery,...or a smaller, lighter-weight motor operating thru a reduction-gear drive and driven by a smaller, lighter battery. If this reduction-gear drive were then reversed to drive the starter motor it would spin that motor beyond it's rpm limits and the armature would disintegrate due to centrifugal force.
The typical small turbine can utilize a Starter-Generator because high torque is not needed to begin the rotation, and such turbine-powered airplanes are usually more capable of carrying the added weight of the high-capacity battery system. But if you take the examination to a larger conclusion, you'll notice that larger turbines actually get away from the electrically activated starter motor completely due to weight/efficiency issues. The larger engines/airplanes use air-driven motors to rotate them for start. Such a system would really get heavy, bulky, and out of hand on a lightplane.

zero.one.victor · Post by **zero.one.victor** » Fri Jan 03, 2003 1:35 am

George,have you considered writing an article for the 170 News detailing your generator/regulator troubleshooting tips like you did here? It'd be great for those members not participating in these forums. And it'd be easier,in my opinion,to look up at some later date when I need the information. Hope ya go for it....

Eric

Post by **GAHorn** » Fri Jan 03, 2003 6:34 pm

Thanks for the encouragement, Eric. But if I did that, I'd have to make certain that everything I wrote was absolutely verifiable....and I made all that stuff up!

Post by **GAHorn** » Sat Jan 11, 2003 6:36 pm

A simple test of your generator on the airplane is to clip a jumper onto the small terminal of the generator and ground the other end. If the generator produces current above 1400 rpm, then the problem is not the generator,...it's elsewhere....like the regulator, wiring, or master switch.
Be careful of that Prop!!

And if the gen and reg and wiring all test out (or if you've found a problem and then installed a new gen or reg and things still don't want to work, don't forget to "polarize" your new reg and gen. To do that simply take a short wire and momentarily short across the "bat" and "arm" terminals of the reg while the master sw. is on. Repeat: just momentarily. A brief, fast "brush" across the terminals is all that should be necessary. (Sometimes this is even necessary when one has replaced a battery, etc. A gen and reg take on a small residual magnetism that is used to remember which way the current should "flow", and if that residual magnetism is lost for some reason (very very rare) then a brief re-polarisation is all that's needed.)

David Laseter · Post by **David Laseter** » Thu Feb 13, 2003 7:27 pm

Follow up: The new (rebuilt) generator is working wonderfully. I can turn everything on at the same time and still have positive charge. At 1600 rpm, with nothing electrical on, the amp meter is up around 25.

David Laseter · Post by **David Laseter** » Thu Feb 13, 2003 7:41 pm

On the outboard end of the generator is a band with a hose connection on it. Apparently a hose can be hooked up to this and ram air can be directed on to the generator for cooling? This will be my first summer out of Alaska, do I need to direct cooling air on the generator? Are there other cooling or summer operating procedures ya’ll could pass on concerning the engine?

zero.one.victor · Post by **zero.one.victor** » Fri Feb 14, 2003 7:03 am

My ragwing was "upgraded' from a 35 amp generator to a 60 amp alternator about 2 owners back. But now I'm wondering if it really was an upgrade? Besides the whole alternator versus generator thing,that 60 amp alternator looks awful big and heavy compared to the generators I've seen. There doesn't really seem to be enough electrical load to need the 60 amp capacity of this alternator mod.,I wish they'd just OH'd the generator and called it good.
I don't see that they revised the W&B on either the W&B sheet,the 337,or in the logbook. Anybody know the approx. weight difference?

Eric

Bill Venohr · Post by **Bill Venohr** » Fri Feb 14, 2003 4:43 pm

David,
I would think that with no electrical load and with a charged battery, you should have essentially no indication of charge on your ammeter--the reading should be 0. You might have been seeing a charge on your battery from starting, but eventually it would be charged up and require very little charge. As you add electrical load, you should see a corresponding and appropriate increase in current flow on your ammeter.

David Laseter · Post by **David Laseter** » Fri Feb 14, 2003 5:34 pm

Thanks Bill for catching that!
After I read your reply I had an instant tail-gate meeting with 2 of our facility electricians whom agreed with you. My battery is probably low, because I flew around for 1/2 hr without a generator and all the running to troubleshoot. What you pointed out is still puzzling however, when load was added, I got a drop on the meter. When I ramped to 1600 it read ~25 and dropped with each additional load. I didn't fly around or anything, just tested it. Hope this is just a Battery that will charge up when I get to go flying?
Thanks again, I'm on the Slope (-36F) so it will be 2 weeks before I can find out.

The International Cessna^® 170 Association

Delco Generator

12V-35amp Generator