Voltage fluctuating
#1923820
10/02/15 12:05 AM
10/02/15 12:05 AM
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Joined: Jul 2010
Posts: 42 Ca
MikeT
OP
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OP
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Joined: Jul 2010
Posts: 42
Ca
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Pulling my hair out on this, did a lot of searching and cant find anything that's worked so far. So I am looking for any ideas. I have a 75 Ramcharger with a 440, MSD ignition, Mopar per VR. Most of the engine bay wiring has been replaced, interior wiring is mostly stock but in good shape. I recently installed electric fuel pump with relay and tuff stuff 100 amp alt. Now I have a voltage fluctuation that you can hear in new pump and see in all lights and volt meter, Its is worse at idle but there at all rpm's. Things I've tried: Checked all grounds and connections. Tried Three diff VR, using mopar per now. Disconnected fuel pump, still fluctuates. Moved the field sensing wire from 12v ignition to battery distribution junction and the voltage is steady as a rock at 14 volts, of course this will drain the battery if left there. Anybody have any idea what to look at next? Alt? Ign switch? Thanks for any help.
Last edited by MikeT; 10/03/15 05:04 PM.
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Re: Voltage fluctating
[Re: MikeT]
#1923898
10/02/15 01:32 AM
10/02/15 01:32 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Posts: 36,041
Lincoln Nebraska
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(1) pull/check/clean/replace the brushes that are in there now (2) as you noted sub in another alt.
live every 24 hour block of time like it's your last day on earth
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Re: Voltage fluctating
[Re: MikeT]
#1924042
10/02/15 11:46 AM
10/02/15 11:46 AM
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Joined: Feb 2003
Posts: 8,680
Andrewh
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Moved the field sensing wire from 12v ignition to battery distribution junction and the voltage is steady as a rock at 14 volts, of course this will drain the battery if left there.
put this on a key on relay. your ignition switch shouldn't matter now. you have bypassed the reason it could be an issue, by moving the sensing line to a constant 12 volt source instead of passing through the bulkhead, ignition switch and bulkhead again. If you have added a ground directly to the VR case from say the engine or a line from the battery itself then you have little other possible issues other than the alt. If you have not tried a ground strap to one of the bolt holes behind the VR, then try that next and see if you still get it. you might also try reving to say 2k rpm to see if it goes away. still an alt problem then, if you have the extra ground.
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Re: Voltage fluctating
[Re: MikeT]
#1924323
10/02/15 06:14 PM
10/02/15 06:14 PM
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Joined: Jan 2003
Posts: 75,043 U.S.S.A.
JohnRR
I Win
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I recently installed electric fuel pump with relay and tuff stuff 100 amp alt. I hope you modified your charging circuit to handle that alternator , if something tells the alternator to go full current and the wiring is not the right size for 100 amps things are going to get ugly
running up my post count some more .
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Re: Voltage fluctating
[Re: Andrewh]
#1924349
10/02/15 06:45 PM
10/02/15 06:45 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Balt. Md
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[quote=MikeT] Moved the field sensing wire from 12v ignition to battery distribution junction and the voltage is steady as a rock at 14 volts, of course this will drain the battery if left there. You found your problem as the 12 volt ign feed must have a bad connection somewhere before it gets to the volt regulator. I assume you spliced into the blue wire right at the voltage reg with the full battery 12 volts at all times to get the steady voltage reading ? If so I agree with "Andrewh" as you could run a 12 volt wire on a fuse right from the battery to a relay and right to the voltage reg sense wire and of course just turn the relay on with key on volts. As long as the unstable volts at the voltage reg sense wire is not effecting any other circuits then running a hot all the time wire through a key on controlled relay is the best repair as it best to have true battery volts to the reg sense wire and the relay controlled by the key is the best way to run the shortest circuit to the reg of true battery volts so it can control the battery voltage best this way by being able to control the field ground and charging rate. Ron
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Re: Voltage fluctating
[Re: MikeT]
#1924412
10/02/15 08:05 PM
10/02/15 08:05 PM
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Joined: Jan 2003
Posts: 15,408 Omaha Ne
TJP
I Live Here
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I Live Here
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Posts: 15,408
Omaha Ne
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Pulling my hair out on this, did a lot of searching and cant find anything that's worked so far. So I am looking for any ideas. I have a 75 Ramcharger with a 440, MSD ignition, Mopar per VR. Most of the engine bay wiring has been replaced, interior wiring is mostly stock but in good shape. I recently installed electric fuel pump with relay and tuff stuff 100 amp alt. Now I have a voltage fluctuation that you can hear in new pump and see in all lights and volt meter, Its is worse at idle but there at all rpm's. Things I've tried: Checked all grounds and connections. Tried Three diff VR, using mopar per now. Disconnected fuel pump, still fluctuates. Moved the field sensing wire from 12v ignition to battery distribution junction and the voltage is steady as a rock at 14 volts, of course this will drain the battery if left there. Anybody have any idea what to look at next? Alt? Ign switch? Thanks for any help. You have already isolated the issue. think about the following statement Moved the field sensing wire from 12v ignition to battery distribution junction and the voltage is steady as a rock at 14 volts The VR sense line is what tells the VR to turn the field windings on and to what degree. This in turn controls the alternators output which correlates to Voltage. By doing the above you bypassed the existing voltage sense wiring and the problem went away. I would say your voltage sense line is fluctuating thereby creating the alternator to do the same. Now the question is what is causing the fluctuating signal. It can be anywhere between the battery, and voltage regulator. the two notorious locations are the infamous bulkhead connector and the connections to the ammeter itself. The following may help
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Re: Voltage fluctating
[Re: MikeT]
#1924451
10/02/15 09:07 PM
10/02/15 09:07 PM
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Joined: Feb 2003
Posts: 8,680
Andrewh
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sorry, I guess I misread. I read your sensing line was rock steady, not alt output voltage. if so, then I agree with above, your sensing line was the issue, but it will be hard to tell why. as I stated before, it passes through the bulkhead twice and then to the ignition. each one of those can cause the voltage loss or change to cause your vr to read differently causing the fluctuations.
putting it on a relay, or rewiring the bulkhead then changing out the ignition if that isn't enough are your only fixes.
if I read correctly the first time and it is still bouncing even after changing where the sensing line gets voltage, then what I said above is still true, add a ground.
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Re: Voltage fluctating
[Re: Andrewh]
#1924566
10/02/15 11:34 PM
10/02/15 11:34 PM
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Joined: Jan 2003
Posts: 15,408 Omaha Ne
TJP
I Live Here
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I Live Here
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Omaha Ne
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sorry, I guess I misread. I read your sensing line was rock steady, not alt output voltage. if so, then I agree with above, your sensing line was the issue, but it will be hard to tell why. as I stated before, it passes through the bulkhead twice and then to the ignition. each one of those can cause the voltage loss or change to cause your vr to read differently causing the fluctuations.
putting it on a relay, or rewiring the bulkhead then changing out the ignition if that isn't enough are your only fixes.
if I read correctly the first time and it is still bouncing even after changing where the sensing line gets voltage, then what I said above is still true, add a ground. AGRRED!!! GROUNDS will wreak havoc with the charging system. one can run a good large size jumper form the battery, to the engine / alternator / regulator and see if the problem improves. If not one is back to the positive side and it's multiple locations to induce LABOR, LOL
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Re: Voltage fluctating
[Re: TJP]
#1925245
10/03/15 10:46 PM
10/03/15 10:46 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Lincoln Nebraska
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yes definitely find out if it is an alt or if it is a wiring prob (keep us updated!)
live every 24 hour block of time like it's your last day on earth
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Re: Voltage fluctating
[Re: TJP]
#1925275
10/03/15 11:52 PM
10/03/15 11:52 PM
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Joined: Feb 2003
Posts: 8,680
Andrewh
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Posts: 8,680
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AGREED!! The proposed band aid will work, but, to a point. It fixes the fluctuating voltage BUT, the root cause of the issue which is a bad connection somewhere on the feed side of the "Sense" line. This circuit also feeds everything else in the vehicle and may lead to an unexpected MELTDOWN somewhere down the road due to the root cause not being addressed. The Band-Aid is not a fix I would recommend or let out the door of my shop. I think based on what op said before, that the internal power feed is coming from The dash power feeds through a bulk head stud in firewall and removed from wire harness bulkhead connector. so it sounds like it is really only power coming out that is causing this. so I wouldn't expect a melt down if he leaves this fix in place. The fact that it just started after adding a new pump makes me wonder though, where did you wire in power for the pump?
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Re: Voltage fluctating
[Re: Andrewh]
#1925671
10/04/15 04:55 PM
10/04/15 04:55 PM
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Joined: Jan 2003
Posts: 25,852 Rio Linda, CA
John_Kunkel
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Rio Linda, CA
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Ever wonder why modern cars have so many relays? To avoid having to run the main power for ignition and all accessories through the ignition switch.
The OP has a bad ign. switch or a faulty at the ign. switch connector...the fact that jumpering the field feed to the battery solves the problem eliminates the alternator.
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