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richp

Starter/Generator - Gen light on

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richp
I'm thinking about buying a 3410 that has a charging problem. The generator light is on, and the seller believes it's overcharging. The voltage regulator was replaced, and the problem is persisting. The starter/gen was checked at the auto part store and seems to be working fine. Any other suggestions? Is regulator output adjustable?

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Al
This starter-generator [SG] has 2 fields, one a very heavy series one for starting and another shunt wound one to charge. The shunt one is connected to the armature, A terminal the other end is connected to the F terminal of the SG. to charge the f terminal is grounded by the voltage regulator. When the voltage at the reaches a level about 12.8 volts the cutout contacts in the regulator close and connect the A to the battery. As long as the voltage at the A terminal is higher than the battery current will flow to the battery, charging it. The charge light is connected through the switch to the battery on one side and the A terminal on the other side. With the key on and 12 volts on the battery side of the light and nothing on the A terminal side [generator not generating] the light gets its ground through the armature in the SG and is on. As the SG starts to turn At idle speed the voltage at the A terminal approaches 12 volts the bulb has 12volts on both leads and no differential between its 2 leads and is out. As the voltage increases to about 12.8 volts the "cutout" terminals of the regulator close and effectively bypass the light leaving no voltage accross it [out]. As the engine speed increases the SG out put goes up and more current flows to the battery. When the voltage reaches 14.2 volts OR the current reaches about 8 amps the contacts in the voltage regulator "VR" that ground the field term of SG open, internally there is a resistor accross them. This reduces the current that flows through the field, reducing the magnetic field in the pole pieces that provide the field for the armature. voltage at the A term. of SG drops, this causes the contacts in the field circuit to close and this brings the output back up and then it goes too high and they open again and the cycle repeats. The voltage regeulator contacts regulate the output by vibrating constantly. The output of the SG is controlled by the tension on the spring on these contacts. The regulator is calibrated by adjustment of this spring. the other contacts "[cutout contacts]" connect the A term to the battery when the voltage when the voltage at A is above about 12.8 volts and disconnect at about 11.8 to 12.2 volts this prevents the battery from discharging through the SG armature when its output is form 0 to 12 volts. If the unit starts OK but don't charge, is the gen side field and or the voltage regulator. Since these SGs are a combo and only have one gen. field coil they only produce about 5 to 10 amps max. If the regulator contacts stick and keep the F term grounded at all times [called full fielded] the SG overheats and the generator field burns out. We replace these commonly. NOTE: If they are burned out most commonly the regulator caused it. HAVE IT CHECKED HOOKED UP TO THE STARTER GENERATOR!!! You can check the SG unit by hooking a voltmeter to the A terminal and grounding the F terminal. the voltage chould come up to 13 to 14 volts with the engine wide open. If it goes to 15.5 or more the regulator is not connecting it to the battery as these units don't have the capability of going that high into a battery unless it is sulfatated and doesn,t take a charge. If the SG puts out OK you probably have a regulator problem. The A term of the starter gen goes to the arm or gen terminal of the regulator, the F term. to the f or fld. term of the reg. and the Batt or b term of the reg goes to the Battery. Do not get confused by the big Selenoid lead to the Arm term. of SG That puts 12v to the armature to start the unit only and is not involved when the uint is running and charging. If your red light is on it either is not charging or the wire from the light is shorted to ground or not going to where it is supposed to go. Good luck and if you have any questions ask and we'l try to explain them. Al

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tej
Greg, You didn't mention if the system is charging the battery and is the battery holding a charge. In any case it sounds like either a shorted wire or the regulator is wired incorrectly. I bought a 3212 that would start if you put a charger on the battery but the generator would not charge. Before buying it I took a quick look at the regulator and could see that it was wired wrong. It didn't have a charge light but the ampmeter stayed right on zero. I hauled the 3212 home and after rewiring the regulator it worked fine. Tim

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tej
Tim, I don't know if it's charging, or if the battery is holding a charge. The gen light was the only indication of a problem that I know of, but that is info the seller gave me, I didn't do any of the testing myself. I do remember him saying something like, 'now it's over-charging', which I interpreted as, 'it used to be under-charging'. But I failed to explore it. I just learned that he has scheduled the tractor to be looked at tomorrow by a collegue, so I guess I can't do much to help now anyways.

Thanks for your suggestions.
Greg

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StanS
7-13-99 @ 22:43
Al,

Very well said and explained!

Now, if you can tell me why my SG refuses to allow me
to fix it you will have something. This is funny in a
perverse sort of way.

For a while this spring my tractor would start and
charge each week at mowing time. The following week it
would not start. I would troubleshoot, take the SG apart,
examine it, find nothing wrong, put it back together, and
everything would work fine until the next week. Then,
same thing. I finally traced the problem to a poor
ground connection between the battery ground cable and
the tractor frame. Problem fixed. Right! Wrong!

After fixing the ground connection the SG ran hot despite
a new regulator. Most recently I discovered the SG is
again not regulating. I suspect I have cooked the field
coil but do not understand why.

This all started a couple of years ago when one of the
field coil leads on the original field coil broke inside
the SG due to years of vibration.

Strange thing is I recently sold a Cub Cadet that had
a similar problem regarding the SG running too hot.

I'm beginning to wonder if this isn't one of those
strange cases where only OEM (Delco Remy) replacement
field coils will work properly. In my younger days I
found that only OEM armatures would stay in a Chevrolet
if you wound the engine to 5,000 rpm or more. All other
replacement armatures would sling the solder out of the
commutator.

I'll appreciate any tips you may have regarding the
problems I'm having at keeping my SG operational.

Thanks,
Roy

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tej
Al, thanks a billion. That was edumacationable! I forwarded the info on to the seller, and printed a copy for myself. Overall, it sounds like there can only be a couple of problems, so sounds pretty solvable.

Thanks,
Greg

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Al
Roy, We see some things like that. I'm glad that when we have to eat a bunch of hours on a weird problem, we aren't the only people that get frustrated. Now a little more about the SG. One of the most difficult problems to find in a generator or alternator is the flying short. Since the armature in a generator is belted up 3 to 4 times the crank speed, on one of these tractors this means it is turning between 10 and 15000 rpm. 243 brs are spec.d @ 4000. Centripetal force is trying to make it fly apart, and the wire in each turn is pressing hard against the wire outside it in the coil. Varnish is the only insulation on the wire. The whole coil is pushing against the fish paper and the retainer strips. Any of these areas is vulnerable to shorting. When the unit is stopped and the armature is checked it will check OK both on a leakage test from the commutator to ground and an induced field test on a growler. The short is gone and until it goes in orbit again will be fine. This is a not uncommon problem. You have checked the grounds, if you have any question run a wire from the ground strap on the reg. mount to the engine or SG. {for good measure]. Check that the regulator is somewhat "shock mounted". Next inside the SG check the rear bearing to see if it is loose, hopefully you are lucky enough to have one with a ball bearing in the back. If there is excessive play in the rear bushing, this can cause the brushes to bounce. The commutator being out of round will cause this also. It should be turned in a lathe and the mica between the commutator bars undercut. Since you probably don't have access to an undercutter, you can use a hacksaw blade. Just break it in half and grind the sides down to take the set out of the teeth and make the cut narrower. .015 to .020 deep is good enough. There can be no copper particles between the bars as it won't work if two are shorted together. after you are done an starter/alt shop can "GROWL" it to check for these shorts. They can also do the turning and undercutting if you desire. If the brushes have been bouncing look carefully at the flat side where they slide in the brush holder if they have a little indentation where the 2 ribs are in the brush holder they will very commonly "stick" bounce up and not slide back down to contact the comutator at higher speeds. Often they come down when the engine stops so the starter will work. There basicly 4 versions of SG. short frame and the longer frame. Clockwise and CCW, CCW found most commonly on the Cub Cadets. The short frames were used on engines up to 8 hp and don't have the torque to crank the larger engines. In addition some were ball bearing on both ends and some have a bushing in the comutator end. One of the reasons they run so hot is that they don't have openings in the end frames, and fans like generators do, so the heat stays inside. As for fields, the fields we use are wrapped in fiberglass tape, where the Delco fields are dipped in a soft plastic coating which we have seen "cold flow". We see very few failures from them. Remember the CW units take different field coils from the CCW ones. The brushes are also different from regular generator brushes. They have more copper in them to handle the starting current. Not nearly as much as starter brushes have or it would tear up the commutator. When it is not charging just ground the F term. and see if it charges. {running near full speed] If it does the problem may be in the regulator. One division of our shop rebuilds starters, generators and alternators of all sizes and types big and small, we have 1 person dedicated to this area. We often reset new regulators. If you trace it to the reg. yell and I'll try to help you get it set. Good luck, AL

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Guest
7-22-99 @ 22:57

Al,

Excellent information on SG operation and troubleshooting.

I think, from discoloration in some of the armature wires,
the armature may be partially cooked even though it still
starts the engine. Also suspect the field coil had died
(again). Will look into it when it has cooled off later
this year and I work up the ambition to tackle it.

Thanks,
Roy

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