1974 Plymouth Duster Electrical Problems when hot

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J

Juan Fuentes

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Hey Guys, I have a 1974 Plymouth Duster with a 318 and 904 Automatic Transmission. I acquired it in February and have been getting it road worthy since. Yesterday I went for a 'shake down' on the car before taking it to get the car inspected and while accelerating and got to about 30 MPH the car just died on me. I pulled over and tried to crank but the battery was completely dead. I waited about 10-15 Mins and then the engine cranked over and started (the cranking was slower than usual). I was limping it back home and not pressing on the gas much just letting it coast but it would still die and I would have to wait again to try and crank. The temperature was reading at 180 during this time. When I finally got it back home, I let the car sit for 30 mins and while cranking I was checking the battery and it was dropping to 6-7 Volts. Also the positive battery cable was super hot. All wiring is original and the distributor is electronic not points. If anyone has experience with this issue or can help in anyway, it would be greatly appreciated!
P.S I did not see a ground strap from engine to frame or on the heater box so I will try there
 
Either the alternator or voltage regulator are going south with the voltage reading you got. Like you said, get the engine to body/chassis ground done and have the alternator tested. Personally for peace of mind I'd change them both, but one at a time to see which one was the culprit.
 
You have either a bad battery or starter. Cranking voltage should never be below 10 volts. Check battery first. Charge battery fully. Load test battery, this simulates how the battery reacts to the starter running. If the voltage drops below 10v then the battery is failing under load. If the battery passes, then the starter is drawing too much.
 
Honestly, check your grounds. Everything else might be OK. Grounds are cheap to fix and you need them anyway. Start there.

Cley
 
Murray said:
You have either a bad battery or starter. Cranking voltage should never be below 10 volts. Check battery first. Charge battery fully. Load test battery, this simulates how the battery reacts to the starter running. If the voltage drops below 10v then the battery is failing under load. If the battery passes, then the starter is drawing too much.
Click to expand...
What he said.
With the positive cable getting hot, I would lean towards a bad starter. A normal starter will pull around 90-100 amps (if I remember right). When they start going bad internally, they can pull a LOT more, and that will cause the cable to get hot. It's like this. Plug a small fan into a cheap, thin extension cord, and the extension cord will not be hot. Plug a 1500 watt space heater (12.5 amps) into that same extension cord, and the extension cord will get hot. It was not designed to carry that much of a load. I would drive it to a parts store where they do free electric system tests and see what they have to say. Hook a charger up to the battery for a while first. You have a voltmeter, so start it and see what the voltage is at the battery. With the engine running, you will have about 13.5 - 14 volts if your charging system is working. Less than 12 volts will not charge the battery.
That being said, a bad starter won't cause your car to stall. That would lead me to guess perhaps a bad (or weak) starter, battery and alternator. Without seeing in person, it is hard to tell. With what you told us, it could be all three things or any combination. It could even be a bad ground like @Clelan said. Please let us know what you find.
 
Check your other thread. Please do not start more than one threads on the same subject
 
Update: Put a ground wire from the K-Frame to the engine. The alternator was bad, and the voltage regulator, so replaced both (luckily already had them in stock) and now it is running fine, Thank Y'all for the help!
 
I never want to just "throw" new parts at an old car of mine that has a problem, because many ore sometimes the "new" parts are bad or go South quickly. I always want to diagnose the problem. But...... IF you want a dependable old car to enjoy, realize until or unless you replace old and wore out or just inadequate parts, you will be one the the RoadKill type guys! Maybe why I carry a box of spare parts and tools when I leave the house in that 60 year old car!

Remember, old and bad wiring can set any old car on fire. ie.... Fire extenguisher!!!
 
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