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 Post subject: Voltage fluctuation
PostPosted: Wed Sep 19, 2018 9:19 am 
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4 BBL ''Hyper-Pak''
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Joined: Mon Aug 27, 2018 7:49 pm
Posts: 27
Location: Southern Illinois
Car Model*: 1973 pymouth scamp 225
How much voltage fluctuation is acceptable?

At idle I get slightly over .5 volt fluctation. This affects idle quality and I have traced it down to either the reg or the alternator by removing regulator plug while idling, results in idle quality is improved, vacuum gauge needle smooths out and rpm quits fluctuating.

The car is a 1973 scamp with a dual field squareback 60amp alternator. Originally came with AC although it has been deleted. battery is less than 6 months old. Amp guage bypassed Headlights are on relays, HEI ignition is also relayed. Two #10 gauge wires with fusible links on either end of each are ran from alternator output to battery positive (starter relay lug). Voltage drop test on ground circuit is at most .01. I have the ignition field wire (blue wire) before the relay, is this correct?? Voltage regulator base gets hot (standard motor product 3 months old) while at idle

It does not over/under charge. At idle it charges from 14.3ish to 14.9ish and the alternator it self is noisy. At 2500rpm fully loaded it charges at around a steady 14.6. Ground wire ran from VR case to HEI mounting bolt to Alt case. I tried to test the diodes while running with a DMM and got 31-32 AC volts, that cant be right. To verify i used a different meter with the same results and for kicks I did the same test on my wifes 2004 camry with very similar results(30-31 ACV). I dont think my cheap meter can perform this test accurately. I do get .3 voltage drop from alt output to battery positive with the motor running. Alternator passed the full field test.

I know these old beautys will fluctuate some due to the voltage regulator “switching on and off” but I dont know how much is acceptable and if I am out of the acceptable range what do you guys think I should do next? Have the alternator bench tested? Put my ignition field wire ahead of the ign relay instead of before? I have tried 3 VR so far (had two OLD spares of unknown brands and the Standard one is new) I dont want to wreck the HEI module that I just installed. I have basically went through every wire and find that I get a .6-.7 voltage drop on my ignition run wire before the relay. The only thing I can think of that I havent done is to pull the ignition switch and clean all of those contacts. I’ll shut up now and listen :D

-Josh


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 Post subject: Re: Voltage fluctuation
PostPosted: Sun Sep 23, 2018 5:37 am 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 887
Car Model*:
Since no else is responding ,just a couple of thoughts maybe wrong ones. Alternator, voltage regulator and ignition module should get full battery voltage from the relay. That may be wrong.


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 Post subject: Re: Voltage fluctuation
PostPosted: Sun Sep 23, 2018 9:12 am 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 887
Car Model*:
Ground wire ran from VR case to HEI mounting bolt to Alt case. Ground daisy chains,loops and parallel and non parallel paths,can be very confusing. Alternator bolted,grounded to engine,ground wire to battery, and or separate or additional ground wire to battery.. This makes one path direct to battery. Left over ac pulses,radio or electrical noise and ground current will be adsorbed by battery. By adding that ground wire from HEI and VR case to alternator case , an extra non parallel path to battery has been created,ground loop. Ground return current from alternator will be divided by 2 paths.Some will take primary original path and some will take new secondary path. If the primary path is lost [lose bolts,rust] all current will take secondary path.Just my thoughts on this could be wrong


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 Post subject: Re: Voltage fluctuation
PostPosted: Fri Sep 28, 2018 12:16 am 
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4 BBL ''Hyper-Pak''
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Joined: Mon Aug 27, 2018 7:49 pm
Posts: 27
Location: Southern Illinois
Car Model*: 1973 pymouth scamp 225
Solved (I think)

After reading your post Matv91 I went ahead and pulled the ignition switch and cleaned all of the posts on it and also ran the the ground wire from alt case to hei module to vr case straight to the negative post on the battery and it seems to have helped a lot. My voltae drop of the positive charging circuit went from .6 to .18 and the flutcuation of my idle and battery voltage has calmed down. Thanks for posting a reply! I still would like to get rid of the rest of the drop but if I cant then I wont be hugely dissapointed.

-Josh


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