Undercharging- Alternator Pulley swap?

[Daniel Romero]

So, since these C-body Mopars are reportedly notorious for undercharging I've been researching and have found some information on doing an alternator pulley swap. Has anyone done a pulley swap? Any recommendations on a quality alternator that addresses this issue? I have a 1973 Fury with a 400. I still have my original alternator but I can't find anyone around here that is willing to rebuild it. I did find a resource about the pulley swap but I don't know what pulley would be correct and I don't want to end up with an overcharging problem.

Alternator Pulley Size How it Affects the Charging

 

[Big_John]

Rebuilding an alternator is pretty easy. The pulley has to be pressed off to change the front bearing but that's not all that hard with a good puller. But if the bearing is good, there's no reason to replace it.

But usually it's the brushes and/or the diodes that are the cause of the problems and both of those are easy to change in a square back alternator.

 

[Davea Lux]

I would suggest doing an output check on the alternator, see how much load it takes to move the ammeter into negative territory. A pulley change will not help if there are bad brushes or a bad diode. The FSM shows how to disassemble the alternator without damaging it. Also check the ground to the regulator as a bad ground can cause the regulator to go dormant and not properly charge the battery. If your car does not have an ammeter, you can install an off the shelf one at the output lead from the alternator as a test device. As the load is increased, the alternator output should also increase up to it max rating, probably 42 amps.

Dave

 

[CBODY67]

If you're talking about "undercharging" being the negative deflection of the needle at base idle, at night, I don't think anything you can do will change that. My '66 did that when new (we bought it when it had 7000 miles on it). NOT specific to fuselage cars, per se.

Do a charging system check, FIRST. See what it's really putting out at idle. I seem to believe that the production pulley is the smaller one, anyway. I have seen larger ones, but not smaller ones that I know of. Police/taxi units had larger alternators anyway.

Find an "old, embedded" electrical shop. One that was around when the Chrysler alternator systems were on normal, used Mopars. The person running such a shop should know how to rebuild and test them, AND probably do it more reasonably than one of the "modern" shops you might have inquired at. I concur, things are easy to change in them, other than the front bearing. Brushes are a normal rebuild part. Diodes only if they fail (let juice go the wrong way in the circuit), which could require a soldering iron.

The other side of the deal is that for the price of a refurbished alternator repair, you could purchase a reman unit from an auto supply chain, or RockAuto, or similar. With a warranty, except it'll probably be one of the newer versions, with better cooling and such. Maybe even a few more amps?

Find that "old shop", as I mentioned, and you'll probably find somebody that can do a decent job of rebuilding what you have. It'll take some looking, as they will probably be "off the beaten path" somewhat, many times. AND look for an older, embedded auto supply while you're at it, who might be able to refer you to somebody that's been around for a long time, in the vehicle electrical business. Maybe even an auto supply where they still have real books! Using the computer for inventory controls rather than parts look-ups on the older vehicles.

Remember, too, that Chryslers were not designed by GM or Ford, so there will be some quirks they have that the others do not. And vice versa. Some things that Chryslers do that GMs did not do, or not in the same way. Each manufacturer had their own design orientations and priorities back then.

By the way, check the bulkhead connector for the "10 gauge red wire) that goes from the engine compartment to the ignition switch. Check for corrosion at this point. ALSO, make sure that both the battery terminals and the cable ends (+ and ground cables) are clean and bright. On a modern system, a little corrosion at that point can drop effective alternator output by 10%. In other words, make sure that all charging system connections are clean and tight! AND that the hot base idle speed is to spec.

Happy hunting!
CBODY67

 

[Gerald Morris]

A GOOD voltage regulator and good alternator will help you out the best here. If you're not running anything fancy, a 60 A roundback should do you well. Check your battery too. After a hot summer, my old one finally just withered away. It was a big Mopar battery, only 18 months past its dead date, so I have no complaints there. Replaced my regulator too, just to be safe, and it does just as well as the previous one, which I'm keeping as a spare. Bought a big Exide Size 49, modded my tray to hold it and all is swell with my electrical system.

 

[Ross Wooldridge]

Back in the day to address this problem they made an adjustible voltage regulator which one can adjust up a tad to minimze or eliminate idle brown-out like one can experience at night when you've got your AC and lights on etc.

They are found on eBay - I just bought two NOS ones.

Search eBay (like this):

mopar adjustible voltage regulator in eBay Motors | eBay

 

[Daniel Romero]

That’s awesome!

I had no idea such a thing existed. Thanks! I’ll have to read into it and figure out how to properly adjust it but that sounds like that would do the trick. Anything a novice should be aware of when installing one of these?

 

[CBODY67]

The adjustable voltage regulators were usually put on cars that saw lots of short trips where the engine didn't really run long enough to re-charge the battery after the car started. So the charge settings could be changed to let the alternator charge more than normal in such situations. If you were going on a long trip, you'd need to dial it back to normal so as to not over-charge the battery, affecting it's ultimate service life ("cooking-out" the electrolyte, so to speak). I found a NOS one about 20 years ago. Genuine Chrysler Parts, but not "production" Chrysler parts.

CBODY67

 

[Gerald Morris]

Here are some modern, heavy duty adjustable V regs from the same folks who ran the article on pulley size. I like the high current stators they're selling too. IFF I ever need more than the 60A my Duralast provides, I'll likely go get a junkyard core, maybe a squareback, rebuild it to higher current and roll with one of these modern adjustable regs. Another possibility would be to pop a good pot into the circuitryof a regular solid state V reg.

Alternator Voltage Regulator Kit, Chrysler Dodge Jeep

 

[CBODY67]

Here are some modern, heavy duty adjustable V regs from the same folks who ran the article on pulley size. I like the high current stators they're selling too. IFF I ever need more than the 60A my Duralast provides, I'll likely go get a junkyard core, maybe a squareback, rebuild it to higher current and roll with one of these modern adjustable regs. Another possibility would be to pop a good pot into the circuitryof a regular solid state V reg.

Alternator Voltage Regulator Kit, Chrysler Dodge Jeep

The reason those are termed "external" is that the kits convert a late model Chrysler Corp charging system to what it was BEFORE the voltage regulator function became a part of the body control module. Hence the notation about keeping the Check Engine light off. Daniel Stern Lighting has had instructions of how to do this on his website for about 10 years, using the voltage regulator from a '68 Dodge Dart, as he mentions. Only thing I saw that might work on a vintage Mopar was the factory electronic regulator (non-adj) that was claimed to be "adjustable".

Regards,
CBODY67

 

[Gerald Morris]

The reason those are termed "external" is that the kits convert a late model Chrysler Corp charging system to what it was BEFORE the voltage regulator function became a part of the body control module. Hence the notation about keeping the Check Engine light off. Daniel Stern Lighting has had instructions of how to do this on his website for about 10 years, using the voltage regulator from a '68 Dodge Dart, as he mentions. Only thing I saw that might work on a vintage Mopar was the factory electronic regulator (non-adj) that was claimed to be "adjustable".

Regards,
CBODY67

Yes, I read the caveat that these "external" regs were such as a means of bypassing the compu-crap controller. I also read these have an adjustment knob. I suspect its a high power pot, as voltage regulation is a feedback loop, be it electro-mech as the original crude heater coil regs from Ma Par were, or as the nice little power FET sorts now ubiquitous on eBay.

 

[CBODY67]

There is another method, computer-controlled, of "voltage regulating". It's done by varying the amount of "ON" time of the alternator output. Not unlike what the old points did, but fully electronic. No resistors or otherwise involved.

When GM went to "volt meters" rather than "amperage gauges", I thought it was a little flaky not to be able to see if the charging circuit was working. Over time, I came to like the "volt meter" orientation which, as GM claimed back then, can give a better display of how the system is operating. Bad cell would equal lower voltage in that system, but in an "amp gauge" system, it could indicate a charge condition continuously.

In about 2014, their light truck clusters have a Volt meter that has a scale going from about 12v to about 14.5v. This expanded section can vary with vehicle operation. Seems there's a different method of electronic regulation of the system. As long as the battery stays charged is all many people are concerned with.

CBODY67