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Author Topic: 16.4 volts at the battery  (Read 4664 times)

Offline shadango

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16.4 volts at the battery
« on: November 26, 2009 - 02:42:22 AM »
Noticed that my summit voltage gauge was reading high....almost pegged...so I checked thevoltage at the battery while running.....16.4 or so.  :22yikes:

The alternator, voltage regulator, wiring harness (Bill evans)...pretty much all the underhood electrics...are new, installed last May or so.

The gauge was running high back then too but that detail got lost until now I guess....so I have been running all summer with it overcharging.....no issues to date other than the high reading.... :dunno:

So what can I check, reading wise, to determine the fault?

The VR was checked at autozone a while back when I was having another electrical issue and it checked out fine....what can I check at the alternator to see if its a bad diode?

In another thread ,someone referenced that the Bob Evans wiring harness could be bad....?




Offline Chryco Psycho

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Re: 16.4 volts at the battery
« Reply #1 on: November 26, 2009 - 02:45:42 AM »
I would just take the alt to a parts store & have it tested , if the wires are in the incorrect position in the bulkhead plug that could be a problem as well you can easily check wire color with a wiring diagram to be sure

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Offline shadango

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Re: 16.4 volts at the battery
« Reply #2 on: November 26, 2009 - 02:50:30 AM »
Holy mackeral that was a fast reply! :2thumbs:

Thanks Chryco.....will check the wiring colors....I have a PDF version of the factory manual.....I think there is a diagram in there.....


Offline shadango

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Re: 16.4 volts at the battery
« Reply #3 on: November 26, 2009 - 02:56:21 AM »
By the way...the stock ammeter is reading normal, right in the middle.....

Looking at the manual, they show two possible reasons for over charging....either a bad VR or a bad ignition switch...

How could a bad ignition switch cause this?

Mine is new anyways.....LOL


Offline Chryco Psycho

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Re: 16.4 volts at the battery
« Reply #4 on: November 26, 2009 - 03:05:58 AM »
the ammeter is off center slightly to the C side when running but close to center .
In my experience an over charging is caused by the voltage reg or the alt diodes only                                                                                                     

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Offline shadango

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Re: 16.4 volts at the battery
« Reply #5 on: November 26, 2009 - 03:26:45 AM »
Just checked the wiring colors....

Everything seems to be OK....though the diagram shows the firewall connectors upside down compared to what they are on the car...LOL

The car runs and the gauges etc work fine, so I think you are right.....gotta be an lt or vr issue....

I guess I will pull them both and take a trip down to autozone tomorrow....assuming they are open.

I just had the alt off the other night when I was installing the new heater hose brace..... :banghead:

Could a bad ground on the VR where it mounts to the firewall cause this?
Scratch that....just realized I have a ground strap from the VR to the valvle cover bolt...so ground should be OK.

Whats strange is I ran like this all summer.....shouldnt I have toasted the battery by now???

If I have the green/purple wires at the alternator swapped (both go to the VR) would that cause this?  No, right?  You posted an answer to a similar question here...
http://www.cuda-challenger.com/cc/index.php?topic=43800.0 which is how I wired mine....green wire in the center connector.

Well, I guess that pretty much rules out the obvious stuff......I have the original VR that was in the car when I got it...no idea if it is good or not....may try swapping it in just to see....see any harm in that?



« Last Edit: November 26, 2009 - 04:04:02 AM by shadango »

Offline Aussie Challenger

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Re: 16.4 volts at the battery
« Reply #6 on: November 26, 2009 - 06:24:41 AM »
  The volt gauge could be faulty, reading too high, some of summits stuff is of questionable quality, check with a multimeter to be sure before taking the alternator off again.   :2cents:
  16.4v is a little on the high side and the battery should have shown signs of boiling, lights would have also been very bright.   :22yikes:
Dave

Offline shadango

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Re: 16.4 volts at the battery
« Reply #7 on: November 26, 2009 - 09:22:11 AM »
I did check at the battery already......when running, around 16.4 volts....with engine off, 12.5 or so.....

Offline 73Chally

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Re: 16.4 volts at the battery
« Reply #8 on: November 26, 2009 - 09:24:15 AM »
If you have 16.4 at the battery, my guess would be the VR.  We just had to replace one in our Super Bee with the exact same problem, except we could smell the battery cooking.  With an ammeter hooked to the battery with the car running, rev the engine and see if the voltage goes up with RPM (alternator spinning faster).

Offline shadango

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Re: 16.4 volts at the battery
« Reply #9 on: November 26, 2009 - 09:36:14 AM »
You mean hook up a voltmeter, not an ammeter, right?

i believe voltage does increase with engine RPM. the 16.4 volts I measured was at fast idle.....the summit gauge also shows pegged....then drops when RPMs go down some....But will double check.

Should I be checking right at the battery like I am or checking at the ballast resister s the factory manual says ?

Is there a way to test the VR myself? The manual just sys to check voltage and if its high, replace it...LOL
*********update

Just checked the voltage at the ballast resister #1 termninal to the VR ground ......14.5 or so volts.....using the battery ground cable, 14.8 volts........According to the manual, I am just about within range......but then checking voltage at the battery itself, 16.2-16.5 volts..... :clueless:
« Last Edit: November 26, 2009 - 09:49:21 AM by shadango »

Offline 73Chally

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Re: 16.4 volts at the battery
« Reply #10 on: November 26, 2009 - 09:53:35 AM »
I did mean volt meter, oops.  What you are describing is the exact same scenario we had.  If it was me, I would go ahead and buy a new VR to try.  If nothing else, if it turns out to not be the VR, you at least have a spare and you're only out $20 or so.

Offline shadango

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Re: 16.4 volts at the battery
« Reply #11 on: November 26, 2009 - 10:22:40 AM »
I have an old OEM VR and decided to try that one....it was reading 15.8-15.9 at the battery and just around the same 14.5-14.7 at the ballast.

Put the other back in and now its reading 15.8 like the old OEM one....down from 16.4.

Ok, now I am stumped. 

I guess both VRs could be bad though.....

Also, looks like voltage is NOT going up/down with the engine speed afterall....hangs fairly steady.
« Last Edit: November 26, 2009 - 12:09:31 PM by shadango »

Online GoodysGotaCuda

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Re: 16.4 volts at the battery
« Reply #12 on: November 26, 2009 - 11:43:56 AM »
Check the voltage at the voltage regulator. If it is getting a low reading such as 12 when its actually 16, it will try to kick the alternator up while running. May have to back probe or stick the wire at some point to do it though. Not too easy.
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Offline shadango

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Re: 16.4 volts at the battery
« Reply #13 on: November 26, 2009 - 12:02:32 PM »
Through which wire?  The blue (purple) or the green?

According to the schematic both go to the fields of the alternator.

Could I just check voltage at one of the field connectors on the alternator?

How can it be reading 12 if its actually 16?
« Last Edit: November 26, 2009 - 12:06:08 PM by shadango »

Offline Chryco Psycho

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Re: 16.4 volts at the battery
« Reply #14 on: November 26, 2009 - 01:10:25 PM »
the blue wire is the 12v feed , the green is the regulated wire

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