--This is the new style battery disconnect switch I have been using.
Works much better than the green knob.
Bob
On 7/6/2025 10:09 AM, 'dave mason' via Chrysler 300 Club International wrote:
I believe I watched a Bob Merritt video wherein he mentions finding a better type of disconnect and swapping out the green knob type for a different type. I like Hank’s simple method of pulling the negative cable as it doesn’t take long if you have a half inch wrench at the ready, and one less thing to go wrong…
Sent from my iPhone
On Jul 6, 2025, at 09:43, 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 etcBMW 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 placeCars / 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 relayThere are two sizes smaller one ok for our cars , like 10$ . Other for LincolnAlso 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 destructionAmmeter 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 picturehope 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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