Alternator

[Plum Crazy 67]

I purchased my 1967 Barracuda two years ago and have been working my way through the list of items that need to be addressed to complete the car to where I want it to be. There is a rather long list of items that I have completed on the car but it is too long to include in this post.
I have tracked down three of the previous owners and the first owner had quite a list of work carried out before he sold the car. Among the list that he completed was the front disc brake conversion, torsion and sway bars, interior and transplanting a mid 1970's 440 CID from a motor home. At the same time long tube headers were installed as well as MSD ignition.
Which brings me to my question. As you can see in the photos it has a large alternator which I believe is a 200 Amp (??) unit from what I can tell. It is charging at 15+ volts which is way above what I am used to on 12 volt system. I have tried two brand new regulators to see if that lowered the charging voltage but without success. I am keeping a close watch on the level in the battery as the over charging would likely cause a low electrolyte level.
My friend who has a 383 with a stock alternator on a run in stand and we compared the attachment set up for his alternator to mine and the brackets are different as are the mounting points to the engine. His 1970 440 6 barrel GTX was not available for comparison as it is the process for body and paint but he says that it is the same as his 383.
So has anyone come across a similar issue of overcharging and/or if necessary replacing the 200 amp(??) alternator?

 

[slantsixdan]

That's the large-frame Chrysler-built 100A alternator, offered starting in '74. Key question is how the PO swapped it into this car. Did they just fetch the alternator and brackets and toss 'em on with the stock wiring? If so…that's a fire just waiting to happen, as described here.

What kind of regulator does this car have? Is there a field-loads relay installed? (info here) What's the configuration/specification of the wire(s) attached to this alternator's output stud, and how is this main charge wire routed/connected?

 

[George Jets]

Reminds me of the 1 wire Alternator conversion I did on my '89 D100 to eliminate the failed computer run voltage regulator.

I used a 60 amp 85 Ford double pulley alternator from Autozone with a 1 wire regulator conversion kit that mounts to back of Alternator.

Puts out 14.3 volts when charging, works great.

Item number
388400976177

I put a 20 amp fuse inline where the charge wire meets the battery.

Mopar Alternator wiring and mopar regulator were eliminated.


☆☆☆☆☆

 

[Mattax]

. As you can see in the photos it has a large alternator which I believe is a 200 Amp (??) unit from what I can tell. It is charging at 15+ volts which is way above what I am used to on 12 volt system. I have tried two brand new regulators to see if that lowered the charging voltage but without success. I am keeping a close watch on the level in the battery as the over charging would likely cause a low electrolyte level.

Dan has identified this as the mid 70s 100 amp alternator.

100 amps is its 'rating'.
Since the engine came out of a motorhome, that would explain why it has the 100 amp alternator on it. it was probably paired with a large battery, maybe two.
In general, the rating is usually near the maximum power it can produce at driving speeds.
In reality it will provide the current (amps) the electrical items want. Not 100 amps, not 50 amps, maybe 35 amps if the lights and heater fan are on with wipers and your foot on the brakes. The wild card is the battery. A very low battery will suck more power than a slightly discharged battery.
If you allow a 100 amp alternator to recharge a very low battery, it could quickly overheat the wiring and/or the battery. Optional heavy duty wiring was available even in the 60s, but you still have to manage the current or the battery will be ruined or worse.

Now lets see if we can figure out why its producing power at higher voltage than it should.
Take a look at how the alternator has been wired up.
According to the master technicians conference, it should have a ground in addition to the two field wires and the output wire.

Browse MTSC by Model Year – 1975 – MyMopar

mymopar.com

Additionally it must have the newer isolated field regulator that can handle the field current it draws.
Finally, the field current should go through a relay, not the ignition switch. The ignition switch and ignition run wires on the car will be overloaded carrying current for the field as well as the ignition. In fact that may be what you are observing with your voltage reading.

^^^^^^^^^^^^^
That may be a lot of info to digest.
Remember voltage is excitement level, and current is electrons flowing (like water molecules that create a stream).
When current has trouble passing through something, it loses some energy (voltage).
If the regulator senses low voltage, it tells the alternator to produce at a higher voltage.

First thing to do is look at the wiring on the back of the alternator and at the regulator to see what is there, how its been connected, etc. See if the regulator is the later version described in the master tech book. See if a relay has been added.

Take and share photos and ask questions.

 

[RustyRatRod]

What I would recommend FIRST would be to put a slow charge on the batree overnight. Mattax alluded to it. If the batree is low, it can cause the alternator to charge more than normal. An overnight charge is free, quick and can eliminate if the problem is the batree. If it charges normally after an overnight charge, you have effectively diagnosed a bad batree. A handheld batree tester can also be useful here.

 

[Dana67Dart]

An overnight charge is free

RRR, now you sound like an EV driver, turn in your Mopar card

 

[slantsixdan]

Optional heavy duty wiring was available even in the 60s

To clarify: you couldn't order heavy-duty charging system wiring as an option. If you ordered a high-output alternator (whichever kind was offered for the year/model being bought), or you ordered a package that included a high-output alternator, such as the grid-type backglass defogger on A-bodies starting in '73, you also got the HD charging system wiring.

 

[RustyRatRod]

RRR, now you sound like an EV driver, turn in your Mopar card

 

[RustyRatRod]

To clarify: you couldn't order heavy-duty charging system wiring as an option. If you ordered a high-output alternator (whichever kind was offered for the year/model being bought), or you ordered a package that included a high-output alternator, such as the grid-type backglass defogger on A-bodies starting in '73, you also got the HD charging system wiring.

So you had to get something like a whole package, like a taxi cab or some such? Some kinda fleet vehicle?

 

[MadScientistMat]

I have a video of what to check if the alternator is putting out too much voltage. This can also be voltage drops or ground issues:

 

[Ricks70Duster340]

What I would recommend FIRST would be to put a slow charge on the batree overnight. Mattax alluded to it. If the batree is low, it can cause the alternator to charge more than normal. An overnight charge is free, quick and can eliminate if the problem is the batree. If it charges normally after an overnight charge, you have effectively diagnosed a bad batree. A handheld batree tester can also be useful here.

They must have them elusive batrees down there in Georgia!

 

[dr dodge]

since those alt are rubber mounted, they need a separate ground
on the conversions I've done, I run a wire the size of the output wire or bigger to the battery ground
just a jumper to the engine can cause problems.
and also charge/test the battery and cable ends for corrosion

(same alt I will be putting on my dart)

 

[nm9stheham]

OP, is there anything in the car that is an unusually large electrical load, that would make it necessary to keep the heavy duty alternator? Or is this car pretty standard as far as electrical parts? If just standard, then an alternator change makes sense to get past these issues.

 

[RustyRatRod]

OP, is there anything in the car that is an unusually large electrical load, that would make it necessary to keep the heavy duty alternator? Or is this car pretty standard as far as electrical parts? If just standard, then an alternator change makes sense to get past these issues.

...and lessen the chances of a burned to the ground car.

 

[Mattax]

To clarify: you couldn't order heavy-duty charging system wiring as an option. If you ordered a high-output alternator (whichever kind was offered for the year/model being bought), or you ordered a package that included a high-output alternator, such as the grid-type backglass defogger on A-bodies starting in '73, you also got the HD charging system wiring.

True. My point was that even with beefed up wiring there are still risks to be aware of.

Rusty's explicit recommendation to slowy charge the battery goes a long way to reducing the dangers of overcharging.

OP, is there anything in the car that is an unusually large electrical load, that would make it necessary to keep the heavy duty alternator? Or is this car pretty standard as far as electrical parts? If just standard, then an alternator change makes sense to get past these issues.

...and lessen the chances of a burned to the ground car.

I agree with your thinking but I thought it would be best to first see how its been wired. A simple change could get past the current hump or maybe the whole thing is a mess (poorly executed) and needs a bunch of work.

Then there is the whole, simple for me, but maybe overwhelming for the OP.

In the photo is at least one pusher fan in addition to the mechanical fan. So there is an additional electrical load. Probably one that can be eliminated with a shroud, and maybe better pulley ratio and/or mechanical fan.

 

[dr dodge]

True. My point was that even with beefed up wiring there are still risks to be aware of.

Rusty's explicit recommendation to slowy charge the battery goes a long way to reducing the dangers of overcharging.





I agree with your thinking but I thought it would be best to first see how its been wired. A simple change could get past the current hump or maybe the whole thing is a mess (poorly executed) and needs a bunch of work.

Then there is the whole, simple for me, but maybe overwhelming for the OP.

In the photo is at least one pusher fan in addition to the mechanical fan. So there is an additional electrical load. Probably one that can be eliminated with a shroud, and maybe better pulley ratio and/or mechanical fan.

or the fan is not relayed
dragging the ignition circuit down

 

[RustyRatRod]

True. My point was that even with beefed up wiring there are still risks to be aware of.

Rusty's explicit recommendation to slowy charge the battery goes a long way to reducing the dangers of overcharging.





I agree with your thinking but I thought it would be best to first see how its been wired. A simple change could get past the current hump or maybe the whole thing is a mess (poorly executed) and needs a bunch of work.

Then there is the whole, simple for me, but maybe overwhelming for the OP.

In the photo is at least one pusher fan in addition to the mechanical fan. So there is an additional electrical load. Probably one that can be eliminated with a shroud, and maybe better pulley ratio and/or mechanical fan.

Oh yeah. I'm not recommending he change anything yet. Looks like another hit & run so far, so we have no way to know how it's wired.

 

[slantsixdan]

So you had to get something like a whole package, like a taxi cab or some such? Some kinda fleet vehicle?

If you bought a heavy-duty package (such as trailer-tow), or you bought certain options that included a 60-or-higher-amp alternator (such as heated backglass), you got heavier-duty charging system wiring. Taxis and cop cars, for sure, but they weren't the only ones.

 

[Mattax]

That's why Del would often call them a "fleet" option but as Dan wrote, versions came with some other options. The electrically heated back glass we've seen a fair number of examples posted here.

For example in this '68 Fleet buyers guide, the optional wiring would have come if the fleet buyer wanted 60 Amp Chrysler or 65 Amp Leece Neville alternators. A 70 amp-hour battery was a requirement with either.

The 1970 Hamtramck Registry - 1968 Canadian Fleet Buyers' Informational Manual - Valiant

I've never seen one in from the 60s in real life and I can't recall anyone posting pictures of one here.

According to the 70s fleet buyers guide, they show a 50 amp alternator but the 71 buyers guide again lists the 60 Chrysler and 65 amp Leece Neville.

The 1970 Hamtramck Registry - 1971 Fleet Buyer's Data Book - Police & Taxi

 

[RustyRatRod]

Got it. So it could also have depended on the options. Thanks yall.

 

[Plum Crazy 67]

Thanks everyone for your input. I will try the simple stuff first such as checking the battery, putting it on a slow charge and seeing if that makes a difference on the alternator output. Then I will check all of the connections, in particular the grounds. When I first purchased the car it would quit and then it would start. What I found was that the ground from the battery had been attached to the inner fender well and was loose. I cleaned it and tightened and it worked until I had the care in for some servicing and had the shop attach a proper ground cable to the engine block. I know that there are some vehicles that add a ground cable from the engine block connection to the frame as well so that may bean additional option. So I think that I will check all of the connections for cleanliness and and add dielectric grease to them as well. Will keep updating as I proceed.

 

[Dana67Dart]

Typically the ground from the battery first goes to the block then secondarily goes to the body and / or core support.

 

[Plum Crazy 67]

I will add the second ground cable from the block to the frame and clean the connections. The specific gravity on the battery is great and it shows 12.7 volts on my charger but I have put on a low 3 amp charge and see what that does to the alternator output when I start the car.

 

[dr dodge]

I will add the second ground cable from the block to the frame and clean the connections. The specific gravity on the battery is great and it shows 12.7 volts on my charger but I have put on a low 3 amp charge and see what that does to the alternator output when I start the car.

the circled stud is for the ground of the alternator
because it's rubber isolated it won't touch ground normally

good luck!

 

[Plum Crazy 67]

In one of the attachments from SlantSixDan it gave part numbers for different regulators. I will see if I can track one of them down