hi sages- ongoing restoration of mechanicals on my80 volare wagon with sl6 and 3spd. no power options except ps. a few weeks ago i put in a used alternator and regulator to remedy a discharged but known good battery. old units were showing 8.8 volts at idle at battery. when i replaced alt and reg. , output at idle showed 14.5 volts. ran fine for a few weeks. battery dead, lights low and needed jump last night. meter across battery at idle shows now 10 1/2 volts. figured alt or reg is bad. connected red wire of voltmeter to black battery wire (shrouded) on alt and black wire to ground. 0 volts on meter. is this the correct way to check alt output and bypass the reg? tomorrow will first replace reg with known good one and see if output at idle changes, if not will switch alt to known good one and see if idle output comes up to the needed 13.5- 14.5v. am i right so far? is there any way to check the regulator itself separately? on some alts with the two field terminals, i have seen a green ground wire screwed to the alt body and then to the block or alt bracket. is this necessary ? i thought the alt was grounded when you bolted it to the bracket and block. thanks tons for your advice. bob f

See here for alternator & regulator testing info and info on ground loops.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

If you do not have battery voltage at the back of the alternator then the circuit between the alternator and battery is open. Usually this is due to an open at the ammeter (and it's shunt in your case).

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Joshua

Yep its an open & shunt case....sorry that'll never happen again.

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<img src="http://farm4.static.flickr.com/3173/2992308402_5481afb26e_t.jpg">

I chuckled.

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Joshua

Y'just couldn't resist, eh? I'm laughing so hard it Hz.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

hi dan and sages- danno your essay which you referred was very well written and precise. when you get the chance you should volunteer to teach english in an urban middle school. anyway i studied it and was stunned, so much so that i had to get a volt of myself. is that one as good as an open and shunt case? sadly i do have a few remaining and probably dumb questions. when i was a teacher i believed there were no dumb questions but times have changed. here goes. based on your pedagogy i will first run a wire from the alternator body to the hold down bolt on the alternator , idle the engine and see if the readout changes. maybe that will solve the problem. if no go, i will swap in another regulator. if no soap then i will attempt this field test by disconnecting the two fields from the alt , jumping a wire from one field to the batt stud on the alt and jumping another wire from the other field to a ground.. and hope the voltmeter on the battery will show much improved output at idle showing the alt is ok. if ng then out comes the alt. not sure what you mean by open shunt possibility in the ammeter. the dash cluster ammeter needle shows slightly to the right, plus charge. last question - does connecting the hand held voltmeter between the batt stud on the alt and ground at idle show whether the alt is bad? when i did that meter showed 0 volts. thanks tons. bob f ps- dan glad you remembered the standing offer in fla.

hello dan and sages- a few more questions if you will indulge me. following your thread(which i made a copy of and put in my 80 volare fsm), i connected a grounding wire from the alternator body to the bolt which secures the regulator. no change on the voltmeter across the battery at idle. battery is fully charged and shows 12.5 volts. next swapped in a good regulator. no change still shows 12.5 volts at idle. next swapped in an alternator. still shows 12.5 volts. i have two questions which may have led me on a wild goose chase. first if the battery is fully charged(all cells show specific gravity above 1.275), am i right that a working regulator would shut off charging of the battery, so the normal charging rate of 13.5-14.5 v would not show at the battery terminals? ammeter on dash shows charging at idle. should i be able to consistently get 13.5- 14.5 v normal charging rate at the batt stud on the back of the alt and ground from a voltmeter since that appears to bypass the regulator? thanks for staying withme on this. regards bob f

12.5V is not an acceptable charging voltage. If battery voltage is not present at the output terminal of the alternator the circuit between the alternator and battery is open.

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Joshua

Whenever the engine is running, line voltage should be no lower than about 13.2 and no higher than about 14.4, whether you measure at the alternator's B+ output terminal or the battery positive post. There is no terminal on the alternator that "bypasses the regulator". I don't see where you've done the full-field test. I do think you will benefit greatly by buying these three books as quickly as you can to get a clear understanding of how your car works.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

hello dan and joshie- i do have those three books. bought them on dans recommendation. have done the other tests but not the full field test yet, maybe tomorrow. my thinking was correct then regarding the proper line voltage of 13.4- 14.4 v and 12.5v being ng. but wait if the battery is fully charged should the volts at the battery terminals while idling still show 13.5- 14. 5 coming in? wouldnt the regulator sense the fully charged battery and cut off the charge? checked the battery voltage at the terminals with the engine off in the buick and it read 12.3 v. i started the engine and it went to 14 v. which is within the green line for alternators on themeter. gut feeling until i do the field test is that the alternator is ng and not putting out the needed charge. am i mistaken somewhere in my analysis? thanks bob f

Is this true? If so please reread my first and third posts. But if you started the vehicle and the battery voltage increase this cannot be true.

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Joshua

Yes, while running you should have about 14v.
Yes, the battery's state of charge makes no difference.
No, it should still measure about 14v.

Danny

hello joshie and 65dodge danny- thanks for your inputs. left out a fact in this ongoing melodrama. bench charged battery between first and later tests. clear now that charging voltage should be 13.5- 14.5v at battery or back of alternator at all times when idling, regardless of regulator behavior. will do sl6dans full field test. charging voltage at idle and back of swapped alternator remains at 12.5, which is clearly unacceptable. still think theswapped in alt is also ng. will report further results of test. these auto stores will test an alternator. may take it out and try that. on the possibility of the ammeter being open do you mean the ammeter on the dash is crapped out and not allowing the charge to the battery? the needle clearly shows charge to the right of middle when idling. thanks for staying withme on this one. bob f

The older cars with the older low amp alternators can have low voltage at idle.............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes