Re: {Chrysler 300} Generator smoking, alternator conversion?

On Sun, Jul 6, 2025 at 8:36 AM John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:

yes alternators have diodes that pass current in only one direction , it cannot run back into it . Diodes are generally extremely reliable things, and usually they fail by going open, “ bond wire “ inside it melts.
One could add a big 50 A diode in series with the A terminal of a generator , but where does this end.? fusible link is easy , protects harness too

Thinking more about the first post—- , why do the reverse current relays not open ? first thought is the pulloff spring was set up too weak at the factory . The new VR itself is probably good but quality control of adjusting is just not there . Remote possibility contact points welded shut if made of junk . Old ones are silver alloy , ($ but wont weld) would still be welded if you look .

Overseas knock off ? = keep your real one … moderate wavering of ammeter needle is normal with a mechanical VR , depending on battery state of charge . Will come and go. How it works as the points move on and off .
One could measure the spring length on the defective cutout relay with a caliper ,( to ID it , it has two windings and an open contact at rest) bend lower mount tab to make spring 7-10 % longer ? Stronger more positive action . Check it closes ok at start up after. . the design worked ,on millions of cars, they do not burn up .

That and add the fusible link, just in case . Fusible link protects harness too from shorts , Burned harness almost totals the car , it did total it in the day— more likely by a short to ground than VR
I have seen two 57-60 300 / mopar with completely burned harness , not pretty . Both had shorted at the upper left kick panel inner fender where the heavy main wire goes into the kick panel over a very sharp punched metal hole edge, to feed breakers in there , I slit vacuum hose and snap over that edge with WS cement If it rests there , vibration can cause cut through .
fyi jkg

On Jul 6, 2025, at 9:54 AM, michael johnson <mikeljgt350@xxxxxxxxx> wrote:

I find it interesting that bI have had classic cars (almost 20) for over 25 years and had disconnects on all of them, but this F is the first I have had that had a generator, all the rest are alternators. I had never shut off the batteries on the alternator cars except for short periods and to qualify for entry into indoor shows and judging. I have never had this happen to my alternator cars over all those years and all those cars. I guess this is just a generator car issue?
Mike

On Sun, Jul 6, 2025 at 7:43 AM Tom Wilburn <tomwilburn1@xxxxxxxxx> wrote:
Don, John and all,

Very grateful for this thread.

I am almost as old as my F, and worked in my dad’s Texaco station in the 70’s - but had no idea about this fire risk.

I see the emails about disconnects that did not work well - is there a particular brand or type that works well? Must they be removed to show the car?

Tom
Sent from my iPhone

On Jul 5, 2025, at 7:05 PM, John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:

one thing on battery disconnect , or removing batt leads .—
If you ever do that switching off by accident, or someone “ helping you out” say accidentally , while the car is running , on alternator or generator, the voltage can leap to 20 + volts, with no battery to load it, — that will blow up your radio and any electronics you may have in the car . Later 300 that includes electric VR or orange box.
This was a huge problem when FI and emissions computers first came , as 2000$ PCU was gone in seconds. Ideas show up like , “see if it runs without battery — means charging is ok “ ( really!!)
It is obvious to warrantee returns if CPU is overvolted when they look inside , so no warrantee . Also idiots in airport garages have 24 or 12 , some think 24 “starts it faster” I lost a bunch of MB $ electronic stuff that way at Logan airport I SAW him do it , later denial , of course

This no battery and running was called “ load dump “ , note that loose battery cables (or back yard battery swap, “leaving it run “) can do it too .

Motorola came out with a load dump protector for cars essentially a huge Zener diode that clamped volts on main lead to 16 max or so . Cheaper than changing radio , FI etc
BMW has 90 computers on CAN bus now … sometimes two batteries , it still goes dead in three weeks . This is progress? 300 looks pretty good. My slant dart always starts in spring , I do nothing . Toyotas too , they get 8 years on battery.

Maintainers boil battery dry … especially fancy automatic ones

Any way , maybe a lock on the switch or think twice before doing switch in first place
Cars / RV burn due to homeowner “ tapping battery “ for 12 v stuff he added no fuse

Note that even this gen burn ( and / or harness ) would have been prevented by Ford type fusible link where the main harness wire connects to battery at start relay
There are two sizes smaller one ok for our cars , like 10$ . Other for Lincoln
Also I have used 60 A electrician type fuse there , on custom restoration like old Packards ( can put 35 to 60 A fuse in the 60 holder)

Ymmv , just sayin … heads up .
jkg

On Jul 5, 2025, at 5:02 PM, John Nowosacki <jsnowosacki@xxxxxxxxx> wrote:

Totally agree with Don.
While I no longer have my 55 or 57 generator equipped 300's, I still have alternator equipped G and Hurst cars. The batteries are only connected when the cars are in use. While I love driving the cars, having more than one (also have a 2006 Magnum SRT-8 for use in some cruise nights that cater to newer toys) means often times hours turn into days, and days can turn into a week or more in between drives on one or the other of the 300's. I even disconnect the batteries while parked at the car show or cruise night, especially if trunk lid or hood are propped open for display purposes.
My sister and brother-in-law had two of their previous camper/RV vehicles go up in smoke, burned to the ground, while just sitting still a few days after returning from trips. Better safe than sorry.
True confessions from a cheapskate- At an earlier stage in life when I had too many 57-74 Chrysler powered vehicles using Group 27 batteries, I made the decision to only have two batteries, since I could only drive one car at a time. Why have 6 or 7 batteries to maintain/replace in the fleet? That one battery that got moved from car to car lasted over 8 years, maybe partly because it wasn't just sitting doing nothing for prolonged periods?

On Sat, Jul 5, 2025 at 3:25 PM don petty <donlpetty2@xxxxxxxxx> wrote:
Always disconnect battery when parked. Lost too many 300 s this way

On Sat, Jul 5, 2025, 1:21 PM Dyke Ridgley <ridgleyracing65@xxxxxxxxx> wrote:
Joh Grady has done a great job in explaining what has happened. I had the same thing happen to me on another car about four weeks ago. Luckily, I was in the car, turned the engine off and saw the Amp gauge peg on discharge. I ran around the car and turned off the battery switch, so no damage. A new regulator and was good to go.

I would also vote for staying with the original style generator. You may very well find a good electrical rebuilder who can source an new armature, if needed, or have the old one rewound.

Dyke Ridgley

On Saturday, July 5, 2025 at 3:12:38 PM UTC-5 jkg wrote:
hi Mike most likely your voltage regulator reverse current relay failed to open which disconnects the generator from the battery when you stop the engine .

Otherwise , battery current will run into the generator and try to drive it as a motor . As it is held by the fan belt , cannot turn it will burn up .
.So likely nothing was wrong with your generator but it is burned up ( likely armature ) now .
Has anybody been inside your regulator lately ? Normally that function is very reliable . This usually happens if someone presses down on one of the relays , the reverse current one, it locks in if you do . Only way to release it , if it happens is disconnect battery . Of course it is possible the relay spring fell off / broke or the fine wire coil corroded open . There are two windings on the reverse current , or “cut out “ relay one for voltage ( fine wire) one for current ( heavy wire ) —- when the current reverses in heavy wire ( = discharge at engine stop ) it fights the voltage coil magnetism and it pops open ; when you start the car it is open still , but gen volts quickly build up , pull it closed , charge current adds to volts magnetism pulls it even more closed . Until you stop .
So Get new VR , dont just replace gen , as a new one will burn up too . Check harness wires for melt too . You are lucky you went out …
Can lead to harness destruction

Ammeter tells you all this .

I would get a used gen , keep F stock, Murray Park etc , just get new brushes , you are good to go Many if not most 35 A dodge Plymouth chrysler 57 60 non AC have same parts inside , watch number of grooves , — of course best to get one the same , they can be clocked differently for F mount , send him a picture
hope this helps ,
John

On Jul 5, 2025, at 3:43 PM, michael johnson <mikel...@xxxxxxxxx> wrote:

I returned from a cars and coffee event this morning, parked my 300F in my garage, and it was running fine. About 30 minutes later I went back to the garage to get something I left in the car, and the garage was full of a whitish gray smoke. I opened the hood of the F and the generator was smoking heavily. I checked the battery and it was at 10 volts and would not start the car, I put a battery pack on and the car started but the amp gauge pegged discharge, so I shut it off an disconnected the battery.
I am assuming the generator shorted out and is probably toast. I am thinking about getting a new generator but then am wondering if converting to an alternator system might be better. Has anyone done this and how difficult is it? Thanks for any ideas.
Mike

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