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#1
08-23-2015, 10:17 PM
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Is the alternator lamp "picky"?
Generic (not Pontiac) question, posted here because quite a few of you seem to know a lot about automotive electrics.
I am converting a 1 wire 10SI alternator system that was on my '52 GMC pickup when I bought it to a 3 wire system. This requires adding an "idiot" light for the alternator system. I have successfully tried a #53 lamp, but I'd like to use something smaller and easier to mount. Question: Is the idiot lamp very picky? Can I use almost any 12 volt incandescent bulb? I've tried a 12 volt LED which didn't work. The #53 lamp is used in a lot of dash lamps from back in the 50s and 60s. It is rated at 14 volts and consumes 2 watts.
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My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
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#2
08-24-2015, 12:09 AM
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A .5W or so bulb should be sufficient. The bulb current determines the cut-in speed (when the alt starts to produce output) to some degree. LED's draw about 10mA or so, pretty low.
A .5W bulb draws about 40mA, should help to kick it into operation without creating xtra heat. George
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"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
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#3
08-24-2015, 09:06 AM
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Thanks George. Just the kind of answer I was looking for.
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My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
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#4
08-24-2015, 11:02 AM
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Larger current through the lamp causes lower cut in? My truck idles at 425 RPM. Any reason I couldn't put a 47 ohm resistor in parallel with a low power lamp? That should give about 270 ma flow when the alternator is not charging.
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My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
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#5
08-24-2015, 05:42 PM
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That will work, in fact, OEM harnesses usually have a resistor in parallelel so if the bulb burns out, the alternator will still excite.
George
__________________
"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
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#6
08-24-2015, 10:52 PM
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Thanks George.
I settled for a 12v LED indicator from my local parts store. It pulled 15.6 ma which computes to 800 ohms resistance. I added a 200 ohm resistor in parallel with the LED (160 ohms total load, 75 ma current) and all seems to work fine.
__________________
My Pontiac is a '57 GMC with its original 347" Pontiac V8 and dual-range Hydra-Matic. |
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#7
08-25-2015, 06:57 AM
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Quote:
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