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fixed alternator, now it don't work

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tomj View Drop Down
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Joined: Jan/27/2010
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    Posted: Oct/09/2019 at 8:45pm
more or less. cleaned it up, reinstalled, output rises past 17V with RPM...

'68 American, 199ci six, Motorola 35 amp alternator, no tag so likely rebuilt, and an Echlin VR-1004 regulator. it was functioning but somewhat erratic, with ALT light on at idle, would go out above 1200 or so rpm. but last night driving with lights on, at one stop light (idle) the ALT light would be on, others it would be off, then later on again. so i assumed an intermittent connection.  everything was physically correct it was untouched for probably 10, 20 years and conections etc looked rusty and dusty.

i changed timing set and front seal, which had been leaking badly for years and coated everything in oil, including the alternator. (timing set/seal all went just fine.) cleaned the alt externally, took off isolation diode assembly, sanded contact areas clean, wire brushed the 1/4-20 output stud, new shiny washer and nut, etc. pulled the brushes, they were fine, sliprings slightly brownish, spun the rotor with some 600 grit wetordry on the slip rings, wiped everything clean, reassembled. regulator connections clean and dry (the four pin bullet hermaphrodite "trailer connector" type). regulator properly grounded. the friction connectors on the alt are tight. bearings do not sound great, need replacing soon.

started engine, measured battery minus terminal to alternator frame, and battery minus to ground, both 0.00 volts. i keep the meter minus clipped to the convenient battery minus terminal.

* engine off, alt light on.
* engine idle, alt light on, battery 12.6V, before isolation diode 13.46V (stud for orange wire)
* engine 2000 rpm (BY EAR), battery 17V! stopped testing.

(i probably ran it at 2000/17V for 20, 30 seconds before i measured it, the only electronics on, tach, sound system, Pertronix Ignitor II... didn't die. i consider myself lucky.)

partially unplugged/replugged the regulator connector, and retested. same deal.

i know more or less how the regulator works, sounds like it's just putting battery onto the rotor/field and output maxed to RPM. the funny thing is, i messed with everything *except* the regulator.

the TSM is surprisingly unhelpful here.

any ideas on hoe to proceed?



Edited by tomj - Oct/09/2019 at 9:43pm
1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
sr-ix.com

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2019 at 4:59pm
problem solved with a Delco 10si.

at the recommendation of a friend dropped into this really old-fashioned auto electric shop. been there 45 years, cash only. they don't sell regulators but can rebuild/get parts for the Moto. but for $45 walked out with a brand-new 55 amp 10si, a one-year warranty.  a regulator of dubious quality from RockAuto is itself $44, and i need bearings. and when i'm done i have an alternator with wrong output voltage for modern battery chemistry.

i had a CCI (Canyon Creek Innovations) AM DELCO MOD KIT 19258 in my bins. i reclocked the Delco and had to grind a bit of metal off the CCI bracket to get more inward swing. the stock belt fits. the adjuster bolt did not, so until i get a "GM" type adjuster bracket (wider slot) i found a 5/16" carriage bolt, head/square into the adjuster slot, nut and washer is a pretty good compromise.

the CCI kit came with bracket and wiring components. had to slightly mash the push-on connector on the harness orange wire to grip the new bullet connector, but it would go back, no harm done. wire tied out of the way until i find a better way to clean that up.

(i got the CCI kit from one of those goodie-handouts at an AMO National event, St Louis MO, 1998? how i remembered it was in there i have no idea.)

pulley diameter the same. it's charging at 900 rpm (cold fast idle), 14.6V. voltage at 2000 rpm, 14.6V.

alt light works right.

on the road, improved reliability, lowest cost, no kludges. esmond would approve.




Edited by tomj - Oct/10/2019 at 5:16pm
1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
sr-ix.com

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