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Working on a 66 Chrysler 300, came to me with no low beam…

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Working on a 66 Chrysler...
Working on a 66 Chrysler 300, came to me with no low beam headlights. I found both bulbs burned out. I replaced both and all seamed okay, but I did notice all headlights seemed dim when engine was not running. Checked battery and alternator. Battery passed test but alternator voltage would fluctuate from 13.8 to 15.2. I noticed the car had a new mechanical voltage regulator, so I added a ground from engine to regulator and ground to alternator. Problem was not resolved. I disconnected the charging wire at alternator an installed an 8 ga. Wire directly to battery. Same problem, and when I turned on the headlights with in 30 seconds both burned out again. Next I replaced alternator and regulator with 71 upgrade with electronic regulator, same problem, checked voltage at headlights and found 28 volts while battery voltage is now a steady 14.3 to 14.5. When engine is not running battery voltage is 12.6 headlights 10.0 I' really stumped with this one! Getting tired of replacing headlights. Also noticed no dash lights, haven't checked taillights yet. I believe this has been going on for some time with this vehicle.
Submitted: 2 months ago.Category: Classic Car
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Answered in 1 day by:
5/27/2018
Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago
Roy Belding
Roy Belding, Classic Car Mechanic
Category: Classic Car
Satisfied Customers: 7,900
Experience: Grew up with most of the 50,60 and 70 high performance cars
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hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

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Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

28 volts??? with the new alternator???

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Customer reply replied 2 months ago
28 volts at the headlights, probably all lights because no dash lights are working. Battery voltage is 14.4.
Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

they should be the same voltage as the alternator is connected to the battery.

if you disconnect the regulator, does the voltage drop??

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Customer reply replied 2 months ago
Voltage at headlights or battery. Battery voltage will drop to 12.2 without regulator. Don't know about headlights. Do know when engine is not running headlight voltage is 10, battery 12.6.
Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

thats high resistance in the wiring. you need to load test the wiring from the headlight switch to the headlights including the floor mounted high beam switch

do you have a load pro to check for voltage drop in the headlight circuit??

Roy

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Customer reply replied 2 months ago
Well probably not, never heard of a load pro. Is it possible to converse on this Monday or Tuesday as I am not in my shop now.
Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

sure. load pro is a good tool for load testing circuits for voltage drop. been using it for years.

Roy

https://www.amazon.com/Electronic-Specialties-180-LOADpro-Dynamic/dp/B004IKPUL2/ref=sr_1_1?ie=UTF8&qid=1527448269&sr=8-1&keywords=load+pro+tester

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Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

Please take a moment and rate my service 3 stars or better. that is the only way the site will pay me for my efforts.

Roy

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Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

any update???

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Customer reply replied 2 months ago
I will get car back in shop today.
Classic Car Mechanic: Roy Belding, Classic Car Mechanic replied 2 months ago

ok

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