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post #1 of 27 (permalink) Old 11-14-2010, 04:02 PM Thread Starter
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voltage fluctuation

I've been having problems with the charging system cycling on/off. Tried to track down a shorted wire/connection but no luck so I decided to bypass the PCM & install an external voltage regulator. After reading the posts on here regarding the installation I mounted the new external regulator on firewall, connected field wires from alternator to the regulator according to previous threads. I also connected switched power to the wire at the "top of the pyramid" on the regulator. The system is now charging but is fluctuating from 14-14.5 volts causing a pulsing of the interior lights and headlights. Voltage at the regulator on the two wires coming from the alternator are 14-14.5 volts on the wire with switched power and +/-8-14 volts on the other wire. Is that much of a change in voltage on the other field wire common? Any ideas on how the keep the voltage from cycling & causing lights to pulse? Any help is appreciated.


94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #2 of 27 (permalink) Old 11-14-2010, 07:36 PM
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Do they pulse all the time? Or just after start-up?

Daily Driver: 2004 Ram 2500 Quad Cab 4x4 Long Bed Automatic 5.9l CTD 23k miles and counting, 4" MBRP Turbo Back exhaust 1995 ram 2500 4x4 auto trans
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post #3 of 27 (permalink) Old 11-14-2010, 07:49 PM Thread Starter
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it only happens when running-both at idle and when I increase rpm

94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #4 of 27 (permalink) Old 11-14-2010, 08:02 PM
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yea but just after start up or does it do it after driving for say 20 minutes and you are stopped at a red light...

Daily Driver: 2004 Ram 2500 Quad Cab 4x4 Long Bed Automatic 5.9l CTD 23k miles and counting, 4" MBRP Turbo Back exhaust 1995 ram 2500 4x4 auto trans
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post #5 of 27 (permalink) Old 11-14-2010, 08:08 PM Thread Starter
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all the time-from start up when the grid heater's cycling to when it's warmed up & running as normal--everything seems to be ok other than the .5-1.0 volt fluctuation/pulsing that's going on

94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #6 of 27 (permalink) Old 11-14-2010, 08:38 PM
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hmm...thats weird, pulses are normal while the grid heaters are cycling as they draw a lot. Do you know if they shut off...could be something with them constantly cycling and not stopping like they should once engine temps are up.

Daily Driver: 2004 Ram 2500 Quad Cab 4x4 Long Bed Automatic 5.9l CTD 23k miles and counting, 4" MBRP Turbo Back exhaust 1995 ram 2500 4x4 auto trans
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post #7 of 27 (permalink) Old 11-14-2010, 09:52 PM Thread Starter
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The grid heaters are working as normal--the fluctuation in voltage is very quick (1/2 second or so) and only about 1/2 a volt or so but it does cause a slight flickering in the lights.

94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #8 of 27 (permalink) Old 11-14-2010, 09:56 PM
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thats weird....

Daily Driver: 2004 Ram 2500 Quad Cab 4x4 Long Bed Automatic 5.9l CTD 23k miles and counting, 4" MBRP Turbo Back exhaust 1995 ram 2500 4x4 auto trans
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post #9 of 27 (permalink) Old 11-14-2010, 10:32 PM Thread Starter
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I guess my question is...what is the normal voltage output for the two smaller field wires on the alternator? and is that voltage supposed to fluctuate? I made connections according to this diagram from DTR and as show I am reading 14 to 14.5 volts on the red line in diagram and 8 to 14.5 volts on the blue wire in the diagram. Is this typical or what should it be?

94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #10 of 27 (permalink) Old 11-15-2010, 07:28 AM
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it might be the alternator, the alternating creates alternating current and then an internal regulator converts that to DC....I would find a shop that would test your alternator for free or a few bucks....

Daily Driver: 2004 Ram 2500 Quad Cab 4x4 Long Bed Automatic 5.9l CTD 23k miles and counting, 4" MBRP Turbo Back exhaust 1995 ram 2500 4x4 auto trans
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post #11 of 27 (permalink) Old 11-15-2010, 01:18 PM Thread Starter
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alternator checks out ok--any other ideas?

94 12V 2500 4x4 RCLB, KDP tabbed, pyro/boost/fp, 4" turbo back, BHAF, boost elbow, #5 TST, DSS, 5sp swap complete, Bosch 300's, no FSS, ext volt reg
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post #12 of 27 (permalink) Old 11-15-2010, 08:12 PM
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Did you use an older style mechanical regulator or a solid state one?
The older relay type often cycle up and down a little.

Bill
'95 2500 4wd auto
'95 3500 5 speed heavy hauler
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