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Author Topic: 16.4 volts at the battery  (Read 5486 times)

Offline quagmire

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Re: 16.4 volts at the battery
« Reply #15 on: November 26, 2009 - 01:39:59 pm »
At the regulator, you want to check voltage at the blue wire. 

This is the wire that the voltage regulator uses to both turn on and sense how much voltage is actually in the system.  The voltage regulator controls alternator output by controlling the ground (green wire) to the field windings since it has constant power when the key is on.  If the voltage is too low, the voltage regulator will duty cycle more ground to the alternator field windings.  If too high, it backs down.

So you can see now that if their is high resistance or a bad connection in that blue wire at the regulator it will see less than the real system voltage and command the alternator to work harder, thus making your voltage go through the roof.

Make sure the system voltage matches the blue wire voltage, then make sure the green wire is not shorted to ground.  That will also cause the alternator to work at max output. 

A quick test would be to disconnect the two field winding wires at the alternator.  If the alternator shuts off and voltage drops back down to 12 or so, you know it is a wiring or regulator problem.  If it stays pegged the alternator is shorted internally and faulty.




Offline shadango

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Re: 16.4 volts at the battery
« Reply #16 on: November 26, 2009 - 02:12:45 pm »
quagmire...

I did the last test you suggested....unplgged the two field wires.

The battery voltage went down to 12.2 to 12.4 or so.....

The wiring is new...a Bill Evans harness.....I dont think that would be it....

SO I guess I will try another VR.

Cant get one today.....everyone is closed...go figure...LOL

Just for kicks I reversed the two field wires at the alt......no chamnge...aboyrt 15.6 to 15.9 volts running.

Offline quagmire

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Re: 16.4 volts at the battery
« Reply #17 on: November 26, 2009 - 03:02:52 pm »
Reversing the two field wires at the alternator won't do anything, they are not polarity sensitive.  As long as one is 12v key on and the other is a regulated ground it doesn't care where they are hooked up.


It sounds like the alternator is ok then if it shut off when disconnected.  You may want to just disconnect the GREEN wire and see if the voltage drops.  If it does the alternator is definitely ok.  If not it is shorted internally to ground.

Just because the harness is new doesnt mean you couldn't have a bad crimp on a terminal end or a chafed wire.  It only takes a few seconds to check voltage at that blue wire and ohm check the green wire.  This is just about as basic of a system as they come, with a meter you should be able to diagnose this in a few minutes.
« Last Edit: November 26, 2009 - 03:12:46 pm by quagmire »


Offline shadango

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Re: 16.4 volts at the battery
« Reply #18 on: November 26, 2009 - 08:35:51 pm »
Disconnected the green wire only and the result was the same...just 12.5 or so volts at the battery.

The green wires continuity between the alt and the VR is good.....1 or .2 ohms resistance at the most.....hard to tell....my meters dont want to zero out but pretty sure its between 0 and .2 ohms at the most.

Disconnected the plug from the VR and the blue wire reads only 10.8 volts.  SO it sounds like that is my issue, eh?

The blue wire is actually purple....same color purple as the purple wire at one of the alternator field wires. Coincidentally, the same exact color as the two wires that go to a plug that feeds the carb electric choke.....two wires together going into the same plug.....I disconnected that plug from the choke and no real change....a temporary .5 volt drop or spike when I remove or plug it in....voltage at that plug is 14.8 or so volts.

The only way to see what is going on with the purple wire feeding the VR would be to completely remove the wiring harness from the car and unwrap it and see what is going on.... :pullinghair:

I dont think this matters but I will mention it.....the wiring harness is setup with the plugs for the 4 prong ballast.....a while back I found that one connector (the blue wire at the #1 terminal) was shaky so I pulled it out of the plastic molded plug itself and plugged it into the ballast....leaving the other connector off (the jumper to the other ballast termional on the same side which feeds the green/red wire)...I had read the green/read wire is un-needed with my ECU so I have left it off.....
« Last Edit: November 26, 2009 - 08:51:03 pm by shadango »

Offline quagmire

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Re: 16.4 volts at the battery
« Reply #19 on: November 26, 2009 - 08:48:31 pm »
Bingo, sounds like you found the reason it is overcharging.  That makes perfect sense then, you are losing about 2v somewhere to the VR, and you are overcharging by about 2v. 

That purple wire branches off and powers several components: choke heater, VR, alt. field winding, ignition ECU, and the ballast resistor.  You will need to find out where in the harness you are losing voltage by tracing back through it and measuring voltage at those components.  If they are all reading low voltage, you probably have a problem at the bulkhead connector or ignition switch.

Offline shadango

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Re: 16.4 volts at the battery
« Reply #20 on: November 26, 2009 - 08:53:26 pm »
I am reading 14.5-14.8 at the ballast...so that should rule out the igntion switch and bulkhead then?

Offline quagmire

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Re: 16.4 volts at the battery
« Reply #21 on: November 26, 2009 - 08:59:32 pm »
Yup, you will want to start by piercing the wire with a pin right before it goes into the VR connector and measure the voltage, you may just have a bad connector. 

If not you will need to find where the wire to the VR splices off of that main purple wire.  It should be pretty close to where it branches of the main harness.  You can either probe into the wire until you find the spot wher it jumps back up to 12v or just replace that wire and be done with it.

Basically just work your way down from connector to the splice until you get 12v back, lucky for you it should only be within a foot or so of wire and not over the length of the vehicle.

Offline shadango

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Re: 16.4 volts at the battery
« Reply #22 on: November 26, 2009 - 09:05:35 pm »
Ok, cool...will try that tomorrow....the wife is yelling at me that I am stinking up the house with fumes....LOL

Have never tried the "pin" method...what, just stick a stick pin or needle into the wire itself and use that to connect to the meter I guess?

I guess the part I also dont understand is that if the purple wire is connected to the field of the alt, how does it also provide voltage at the VR, choke etc?  Would there be voltage at the alt end of the purple wire too then?

Offline quagmire

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Re: 16.4 volts at the battery
« Reply #23 on: November 26, 2009 - 09:15:30 pm »
Yes, you are just using a pin to pierce the insulation as little as possible to take a reading. 

When you said you have 14v at the ballast, is that running?

If it is then you probably do have a problem at the bulkhead or ignition switch since the battery voltage is 16v and all of those components on that circuit are 2v lower. 

If it reads that with the engine off, key on ( it could if the battery is being overcharged) then start at the VR wire like I said in the last post.

The field windings need power and ground to operate like any other circuit.  The purple wire gives it a constant 12v when the key is on.  The VR actually supplies the ground to it.  It controls voltage by pulsing the ground  on and off many times a second to maintain 13.5 to 14.5v.  In order to power up and know what the system voltage is, the VR requires that purple wire connection.

That purple wire branches off to power all of those components I listed above, so you should have power at every one of those ends.

Offline shadango

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Re: 16.4 volts at the battery
« Reply #24 on: November 27, 2009 - 03:50:56 am »
Yeah, that  14.8 v ballast, 16 volt battery, 14.8 volt choke, and 10.8 volt VR purple wire reading is while running the engine.....

With the engine off, key on - the battery voltage reads 12.4......the voltage at the purple wire at the alt is 10.8, at the choke its 10.8 , at the vR its 10.8 and at the ballast its 10.8.....there is NOT the same 4 volt drop at the purple VR wire that I have when its running....

So doesnt that rule out there being an issue with that VR leg of the purple wire?

Doesn't the ignition switch power ALL of the purple wire at once? What would cause the voltage to be lower only at the VR purple wire when running but not when the key is on but not running ? If it were the switch or bulkhead, wouldnt the drop be the same on all the purple wires?

And also what i don't get is that the reading at the ballast, according to the manual, SHOULD be about 13.8 - 14.45 at 80* while running, which is what I have (the manual says it can be within half volt)........so I figured I was ok there.    :clueless:
 :banghead: Man I hate electrical stuff.

I have been running the car all summer this way I figure....I want to get it right though...dont want to get stranded one day due to this...

*********update
7am 11/27
I checked everything one more time.

The voltage drop difference doesnt happen at all until I put the alternator and VR back into the equation....ie when its running...

With the VR disconnected, but the alt hooked up (both fields) The voltage at the purple VR wire (disconnected) is 11.8 and the voltage at the choke heater is the same....the VR voltage does drop when I plug the choke back in by about .5 volt.

SO then I stuck a pin in the purple VR wire with it hooked up to the VR (everything else connected too) and the voltage was 15.8 at the wire but less at the battery....

I think I am just going to pull the lt and run it down to have tested and pickup a new VR too.....
« Last Edit: November 27, 2009 - 08:26:44 am by shadango »

Offline shadango

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Re: 16.4 volts at the battery
« Reply #25 on: November 27, 2009 - 01:12:52 pm »
Had the alternator checked...twice, two different places...they say its fine.

Put a new VR in and no real change.

I did find that when I moved the harness plug at the firewall up and down I got about a half volt change.....so looked in to that.

The small brown wire wasnt seated all the way in the plug and the wire for the black wire came out altogether from the plug.

I am SO pissed.    I paid Bill Evans good money for the harnesses and now this is the SECOND failure at a "new" harness connection. I shouldnt have to fix a brand new harness!!! :villagers:

I soldered the brown and black wires to the clips and reinserted....So now at the connector no major change when I move it.

Now my voltage at the battery while running and everything plugged in is about 15.1 to 15.2 volts at idle.  If I unplug the choke heater it drops another .2 volts or so....at the ballast I an getting 14.6 volts....

At least now it seems reasonable compared to the 16.4 I was getting before at the battery.

A an aside, the guy at autozone said that 13-16 volts is considered Ok for battery voltage level.......  :dunno:







Offline quagmire

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Re: 16.4 volts at the battery
« Reply #26 on: November 27, 2009 - 06:49:43 pm »
That's still on the high side, but you can now see the importance of checking the wiring.  You may want to check the rest of the harness connections on that circuit out too, wouldn't surprise me if you still have another iffy connection.  Seems like that harness has some quality control problems.

Offline shadango

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Re: 16.4 volts at the battery
« Reply #27 on: May 07, 2017 - 06:22:31 pm »
Ok...so WOW.....This is an 7.5 year old thread!   

I didnt even realize I had the car that long....LOL

Reviving it rather than start a new one since its the same question part deux.

I just installed the crackedback headlight relay setup so I figured now was a good time to look at stuff electrical again.

Since my original post, I have been running the car with high voltage.......so far, no issues.  In fact, pretty sure I still have the same battery even!

I am still running high.....15.7 - 15.8 when cold at high idle....and it comes down to 15.6 or so when warmed up at idle......havent checked it HOT yet.  This is measured on a voltmeter AND the summit in car voltage gauge.

Now, drop into gear and turn the lights on now and she comes down to very fidgety 12.8 or so and lights flicker etc until I give her gas and bring the rpms up....(before the relay kit it would be a little higher voltage as I recall, so its a true indication that the relay kit IS delivering more power to the lights!).  The car is cammed and has always had a very rough in-drive idle....

Voltage at the BLUE wire at the alternator is 14.8 while running (with the battery voltage showing 15.7 or so)

I disconnected and probed the green wire at the alternator and connected my meters other lead to ground....about 1500 OHM, and that is with the VR plugged in.   Unplug the VR and it goes to no connection......that seems like thats what SHOULD happen....so I think the  green wire is NOT going to ground on its own....just when plugged in at the VR.

I even swapped in another VR, checked its grounds, even ran a separate ground from the VR case to the battery.  NO CHANGE AT ALL.

Wiggled the two wires on the alternator, wiggles wires at the firewall....no change.

The manual says "check the ignition switch circuit between the battery terminal of ignition switch and voltage regulator"

Not sure I ever did that way back then.

Its a different alternator since then, having had one come apart on me on the way to carlisle a couple years ago.....

The main ground at the radiator support up front is clean as is the ground cable from the battery cable to it.....cable to engine is good....all the obvious stuff seems right.

Any new thoughts on my conundrum almost 8 years later???  LOL

Should I even worry at this point ??    :bigsmile:  I mean its been over 7 years....but still, it bugs me not knowing "why".

« Last Edit: May 07, 2017 - 06:55:17 pm by shadango »

Offline dodj

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Re: 16.4 volts at the battery
« Reply #28 on: May 07, 2017 - 10:19:27 pm »
First, clean ALL connections. Valve cover connector, bulkhead connector, fuse link connector, battery connectors, start relay connections, VR ground, and alt connections. See if it changes. (charging voltage)
Scott
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Offline shadango

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Re: 16.4 volts at the battery
« Reply #29 on: May 08, 2017 - 07:11:03 pm »
So how much would the negative battery cable to the engine factor into the system pushing  too much voltage? 

I started messing with that and realized the bolt its attached to (steering pump to black upper bolt) goes into a water jacket....its about the only thing I havent played with.....

The fusible link etc was new when I started having the overcharging state. I used dielectric grease on the connections at the starter relay and they look fine..