Exhausting all options before new alternator

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Marc
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Re: Exhausting all options before new alternator

Post by Marc » Wed Jan 25, 2017 5:27 pm

(duplicate post)
Last edited by Marc on Wed Jan 25, 2017 5:47 pm, edited 1 time in total.

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Re: Exhausting all options before new alternator

Post by Marc » Wed Jan 25, 2017 5:45 pm

66NCVW wrote:...I haven't seen if the bulb would act normally while jumping 12V to the alternator.
It can't. Discounting any circuit resistance, that's the same as putting a wire in parallel with the lamp - with no difference in potential across it the lamp won't glow. Even if the belt broke, you'd still have voltage from the battery applied to keep the lamp out.
Also, with D+ connected to B+ the lamp WILL have a difference in potential across it when the key is off - the "key" side of the lamp has a path to ground through the primary windings of the coil, effectively putting the lamp & coil in series.

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Re: Exhausting all options before new alternator

Post by Dale M. » Sat Jan 28, 2017 10:29 am

Umm.... It looks as if you have covered all the basics but...

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Only thing that comes to mind is you have voltage drop in idiot lamp circuit that is not allowing enough voltage (current/amperage) through lamp to trigger (excite) alternator... Might try larger bulb and run on diode combination...

Something a racer buddy does is using the "run on" diode concept, instead of wire going back to lamp in speedo he connects it directly to terminal 15 (+) side of coil.... It always excites alternator, and prevents run on BUT you lose idiot lamp and you have to test alternator (voltage) at B+ terminal to see if alternator initializes...

Also "some" Al82 alternators need to be spun up to 2500-3000 RPM (throttle blip?) to start charge seems prevalent if you are running a power pulley ...

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Re: Exhausting all options before new alternator

Post by Marc » Sat Jan 28, 2017 5:20 pm

Dale M. wrote:...Also "some" Al82 alternators need to be spun up to 2500-3000 RPM (throttle blip?) to start charge...
I got stranded in Worland WY with a dead alternator last summer, had to wait 3 days for a NAPA rebuilt - it had a label on it showing test-bench results, indicating that it had been tested before boxing up, but when installed it needed to be buzzed out to ~3000+ engine RPM before it would cut in. Persisted until I had a few hundred miles on it, after which it started charging immediately upon startup. I theorize that the field brushes and slip rings weren't making good contact until the brushes wore in a bit.

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Re: Exhausting all options before new alternator

Post by 66NCVW » Thu Feb 02, 2017 10:38 pm

UPDATE: For anyone reading over this thread in the future. The problem WAS the alternator. The new one works perfectly with the regular old bulb and original factory bulb wire.

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Re: Exhausting all options before new alternator

Post by Marc » Fri Feb 03, 2017 1:56 am

A new regulator might've fixed it, but now that they're so hard to get to it's more work than changing the whole thing. Glad to hear it's sorted; was it warranteed at all?

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Re: Exhausting all options before new alternator

Post by 66NCVW » Sat Feb 04, 2017 1:30 pm

No warranty, it was an old off brand bosch copy anyways that had seen better days. B/c I wasn't sure it was going to be the alternator I just put another off brand alternator on it and that sorted it out. Now that I know that was the issue when this one goes bad I'll pick up a nice bosch unit. I appreciate all the help from everyone on here!

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