Alternator - regulator mismatch?

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BobW

BobW

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My alternator puts out 15.2 volts pretty consistantly.
The battery is seeing this same voltage!
I've done the relay splice as recommended by @67Dart273 and thought the problem was solved, as I was showing ~14V at the battery.
I checked it again as I was seeing a bit of battery acid on the top, 15.2V!
I have a Tough One P7509 alternator, Advance shows it doesn't fit my '64 Valiant. I found it is for a later model, the one I used was a '76 Duster and Advance shows it fits that car.
I have the older mechanical Voltage regulator, that obviously isn't regulating!
I also have 2 round back alternators that came with the car, haven't tested them yet to see if they work. I'll probably hook them up to se if they have output, and what goes to the battery.
Can I use the later P7509 by using the later model regulator with the triangular plug?
There's a reason I call tis car 'Bitsa'! ;)
Pics of the current setup and the 2 roundback spares:
Oh, Merry Christmas, enjoy, be safe!

Alt1.jpg


Alt2.jpg


Alt3.jpg


Alt4.jpg
 
It might be an inaccurate VR and it MIGHT JUST NOT yet be getting "true" battery voltage. There are at least two ways to check this.......

One (thanks Dave, KitCarlson) is to measure the IGN terminal of the VR while running at fast idle. Measure from there to the VR mounting flange. If it measures "about 14" then the VR is OK.

The method I use AND DON'T FORGET THE GROUND

is to turn key to "run" with engine stopped. Stab one meter probe into the battery POS post and the other to the VR "IGN" terminal. You are checking voltage drop through the system. There should be almost none, and more than about .3V (3/10 of one volt) means you should check into it

Now run the engine, running at fast enough idle to simulate "low to medium cruise." Make this test first with all accessories off, and again with lights, heater, etc, running. Also warm up the engine and get the battery "up" and normalized.

Stab one probe into the battery NEG post and stab the remaining one into the VR mounting flange. You should read almost zero. Anything actually readable means the grounding from battery to body should be improved.

I like to add a BIG ground wire, using an eyelet -to- eyelet starter cable, no4. On a V8 there are holes in the rear of the driver side head (look at front of pass. head) Run the cable from there to say, the master cylinder studs.

If these checks are OK then replace the VR. "New" does not mean "good."
 
The only mismatch problems I've come across, "generally" are when you have say, a heavy duty alternator and the VR cannot handle the field current. I've done "a few" lashups over the years. For example, if you buy one of the popular aftermarket re-wire harnesses, they expect you to use a "Ford style" regulator

I've used the Mopar 69/earlier style on tractor lashups, and there are several, over the years, "universal" encapsulated regulators. Back in the 80's I used one on my Yamaha 650 street bike. The old Cletrac crawler was swapped with a Toyota 20R and I used a Mopar regulator with the Toy alternator.
 
"Can I use the later P7509 by using the later model regulator with the triangular plug?" Yes, if you rewire the charging circuit to support the later model regulator.
 
6PakBee said:
"Can I use the later P7509 by using the later model regulator with the triangular plug?" Yes, if you rewire the charging circuit to support the later model regulator.
Click to expand...

True I forgot to add. Even so the voltage to the regulator must not have any "drop" or it will also overcharge

Yet another way to check that is to run a no10 jumper from engine block to VR flange, and disconnect the IGN terminal and run a jumper direct from battery, see if the charge voltage returns to 14
 
Your regulator needs a non isolated field (one field wire) typically the round back alternators are non isolated field and have only one wire from the mechanical regulator. FYI, newer 1 field wire regulators available today are internally electronic.


You can use a square back alternator with a mechanical regulator if you ground one of the field terminals on the back of the alternator.

SOME rebulders have been known to internally ground one of the square back field terminals to make it compatable with older cars.

The alternator in your first photo has a ground wire from one of the field wires to ground.

As others have said you can use an electronic 68? and up regulator with some wiring changes.

Assuming you have the correct alt for your regulator, your old mechanical VR might have finally given up (I would suspect that the contacts are stuck closed if you are over charging)
 
67Dart273 said:
True I forgot to add. Even so the voltage to the regulator must not have any "drop" or it will also overcharge

Yet another way to check that is to run a no10 jumper from engine block to VR flange, and disconnect the IGN terminal and run a jumper direct from battery, see if the charge voltage returns to 14
Click to expand...
I've already done the voltage drop test and am using the ignition feed to trigger a relay that runs from the starter relay to the voltage regulator, reading battery voltage.
 
Dana67Dart said:
Your regulator needs a non isolated field (one field wire) typically the round back alternators are non isolated field and have only one wire from the mechanical regulator. FYI, newer 1 field wire regulators available today are internally electronic.


You can use a square back alternator with a mechanical regulator if you ground one of the field terminals on the back of the alternator.

SOME rebulders have been known to internally ground one of the square back field terminals to make it compatable with older cars.

The alternator in your first photo has a ground wire from one of the field wires to ground.

As others have said you can use an electronic 68? and up regulator with some wiring changes.

Assuming you have the correct alt for your regulator, your old mechanical VR might have finally given up (I would suspect that the contacts are stuck closed if you are over charging)
Click to expand...
From what I've seen the newer regulator still uses the two wires, field and ignition in the triangular plug. Correct?
 
BobW said:
From what I've seen the newer regulator still uses the two wires, field and ignition in the triangular plug. Correct?
Click to expand...
The difference is one wire. You UNGROUND the second field terminal of the alternator you showed in the first photo, and tie that to switched 12V "ignition run" on the key side of the ballast

Difference: Old 69/ earlier VR gets IGN run power, feeds that power to the regulator field which is grounded to control field current

New "flat" 70/ later gets ign power to power regulator. Alternator field gets full switched 12V to one terminal. Green wire now "controls the grounding" coming from VR to control field current
 
Bulk head or ignition is bad. I have just been down this road with a 68 super bee. Even after switching to a newer style charging system it sill was charging at over 15 volts . It ended up being a bad harness in the car going to the interior.

100_0150.JPG
 
Oldmanmopar said:
Bulk head or ignition is bad. I have just been down this road with a 68 super bee. Even after switching to a newer style charging system it sill was charging at over 15 volts . It ended up being a bad harness in the car going to the interior.

View attachment 1715656718
Click to expand...
I've already been through that mess. The 'welded' connection under the dash was wired with lamp cord and wire nuts!. New wire run and all soldered.
 
67Dart273 said:
The difference is one wire. You UNGROUND the second field terminal of the alternator you showed in the first photo, and tie that to switched 12V "ignition run" on the key side of the ballast

Difference: Old 69/ earlier VR gets IGN run power, feeds that power to the regulator field which is grounded to control field current

New "flat" 70/ later gets ign power to power regulator. Alternator field gets full switched 12V to one terminal. Green wire now "controls the grounding" coming from VR to control field current
Click to expand...
Ok. To verify I just need to run that field post that's grounded (green wire) to the blue wire on the top of the ballast. Thanks.
 
Oldmanmopar said:
Bulk head or ignition is bad. I have just been down this road with a 68 super bee. Even after switching to a newer style charging system it sill was charging at over 15 volts . It ended up being a bad harness in the car going to the interior.

View attachment 1715656718
Click to expand...
Yeh, Steve I've written hundreds of posts on this. It is voltage drop from the battery throught path to the VR. sometimes the ground adds to the problem The VR MUST see "true" battery voltage.
 
This thread cursed me....

Tonight while driving about 15 minutes from home the alternator quit charging altogether.

It was night so lights were on. Battery was able to supply 11.1v to the system. I knew I had enough juice to get home but to be safe I put it in park and turned off the head lights at stop lights.

5 minutes from home it all started charging again!

After Christmas I'll be running down the problem.

Merry Christmas all
 

This is likely a point of resistance.
upload_2020-12-25_10-41-54.png


Clean that, recrimp and/or solder.
Insulate it!
If there is not enough wire to take apart and redo with heat shrink tubing, use liquid electric tape with or without a wrap of electric tape.
Route the wire up when reinstalling so there is less stress on the wire where it joins the terminal.
upload_2020-12-25_10-47-13.png
 
My battery has been relocated to the trunk, and I use a cable bolted to the frame back there, as the ground. Then I picked up the ground off the body at the front, and bolted it to the engine block.
I then converted my 1968 car to 70-up electronic regulator and
this has been working flawlessly since 1999.
I bolted the regulator to the apron, up where the horn was, and run a very short fieldwire. The horns I threw into the shed, they just get me into too much trouble.
Initially I was using a DC constant voltage regulator but one day it got "stuck" at 18v, so I swapped it out for a generic jobber one that has now worked well ever since about 2002.

I guess probably any alternator could be married to any regulator.
The thing to remember is this;
the regulator "senses" the system voltage off the ignition circuit, and adjusts the alternator output in an inverse relationship to it, until it hits it's preprogrammed hi-limit.
When the regulator senses a low voltage in the ignition circuit, it cranks up the alternator output until it hits the upper limit. If it senses a hi voltage in the ignition circuit, then it cuts back to it's low limit, which could be zero-charge. That device is always targeting a specific voltage that it wants to see, based on it's programming, which is usually between one and two volts above the battery rest voltage, so 13.5 to 14.5 volts.
But if the battery itself has a high internal resistance,or is frozen, then the regulator is gonna command the alternator to work it's heart out trying to jam electrons into it.
 
Last edited:
Mattax said:
This is likely a point of resistance.
View attachment 1715657007

Clean that, recrimp and/or solder.
Insulate it!
If there is not enough wire to take apart and redo with heat shrink tubing, use liquid electric tape with or without a wrap of electric tape.
Route the wire up when reinstalling so there is less stress on the wire where it joins the terminal.
View attachment 1715657011
Click to expand...

Actually resistance in the charge line does not cause regulator / voltage problems. In fact as long as no accessories are sourced from the charge line, the only thing that causes--within reason--is heating up the wire. Of course it can become a problem in just that way.
 
AJ/FormS said:
My battery has been relocated to the trunk, and I use a cable bolted to the frame back there, as the ground. Then I picked up the ground off the body at the front, and bolted it to the engine block.
I then converted my 1968 car to 70-up electronic regulator and
this has been working flawlessly since 1999.
I bolted the regulator to the apron, up where the horn was, and run a very short fieldwire. The horns I threw into the shed, they just get me into too much trouble.
Initially I was using a DC constant voltage regulator but one day it got "stuck" at 18v, so I swapped it out for a generic jobber one that has now worked well ever since about 2002.

I guess probably any alternator could be married to any regulator.
The thing to remember is this;
the regulator "senses" the system voltage off the ignition circuit, and adjusts the alternator output in an inverse relationship to it, until it hits it's preprogrammed hi-limit.
When the regulator senses a low voltage in the ignition circuit, it cranks up the alternator output until it hits the upper limit. If it senses a hi voltage in the ignition circuit, then it cuts back to it's low limit, which could be zero-charge. That device is always targeting a specific voltage that it wants to see, based on it's programming, which is usually between one and two volts above the battery rest voltage, so 13.5 to 14.5 volts.
But if the battery itself has a high internal resistance,or is frozen, then the regulator is gonna command the alternator to work it's heart out trying to jam electrons into it.
Click to expand...

Within reason. There are two basic types of charging arrangements, a type "A" and a type "B". From a website, "A Type-A circuit has the voltage regulator on the ground side of the field coil. A Type-B circuit has the voltage regulator located on the power side of the field coil." Within each arrangement you are correct, but swapping from a 'B' to an 'A' can be problematic.
 
67Dart273 said:
Actually resistance in the charge line does not cause regulator / voltage problems. In fact as long as no accessories are sourced from the charge line, the only thing that causes--within reason--is heating up the wire. Of course it can become a problem in just that way.
Click to expand...
It shure does. We agree there is resistance.
We agree the regulator is only going to know the voltage at its 'i' connection.

Any resistance between the power source and the regulator is going to cause a voltage drop.
It doesn't matter if the drop is in the alternator output line, in the ignition switch, or the bulkhead connections.
Since the voltage reduction varies with current, resistances in the output line can cause the regulator to see much lower voltage than the alt is producing.

Now as far as the battery goes. That I agree will not see excessive voltage from resistance in the output wire. If that's what you're thinking about - battery charging - agree there.
 
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I think I see what your saying. The OP is using a relay. Then yea. if the relay is connecting the regulator Ign terminal to the battery positive terminal.
 
Safest thing might be to temporarily wire the relay so the power comes direct from the alternator output stud.
It might result in lower system voltage than ideal but should stop the battery from seeing 15.2 V and boiling it.

Del outlined testing in post 2. Seems like the right way identify the current problem.
 
Mattax said:
Safest thing might be to temporarily wire the relay so the power comes direct from the alternator output stud.
It might result in lower system voltage than ideal but should stop the battery from seeing 15.2 V and boiling it.

Del outlined testing in post 2. Seems like the right way identify the current problem.
Click to expand...
I've done the testing, found the voltage drop and installed the relay per Del's instructions.
The relay is triggered by the blue ignition wire that originally went to the regulator. the relay feeds battery voltage taken from the starter relay through the ignition triggered relay to the regulator.
The original ignition voltage signal should basically be battery voltage with minimal resistance voltage drop. The ign triggered relay eliminates the voltage drop that was in that circuit.
Doesn't the regulator respond from battery voltage to allow and maintain charging levels?
If I feed the ign triggered relay from the alternator it will see 15.2 volts constantly.
Please note the system worked properly initially, and as someone suggested, the regulator contacts are probably stuck closed.
I'm going with the late model regulator and the wiring change Del mentioned. And I will replace that terminal,thanks for pointing that out.
Happy & Merry Everything!
 
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