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Hello I have a 65 2 door falcon, did an engine swap to a 302 5.0. Engine rebuilt and alternator, battery, starter, ignitions switch arte all new. Problem is I trickle charge the red top battery and the car fires right up at home everytime, but after driving it, it gets harder and harder to turn everytime I turn it off, to the point that it wont turn and has to be jumped. Had battery and alternator checked (autozone), they said the alternator was good and the battery was 100% but it wouldnt start unless I jumped it with a portable jumper, car sounded like the battery was dead. My car has a new starter solenoid but the wire coming from the key ignition switch looks pretty thin, its original, not sure if that could be the culprit. Any ideas?
 

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When the car is running,what is the voltage out put? If the voltage is ok you may have a heat sink problem with the starter.Also make sure you have a good quality cable from the relay to the starter.The thin wire you are talking about does not need to carry a heavy load.Is the starter new or rebuilt? Roger
 

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Hello I have a 65 2 door falcon, did an engine swap to a 302 5.0. Engine rebuilt and alternator, battery, starter, ignitions switch arte all new. Problem is I trickle charge the red top battery and the car fires right up at home everytime, but after driving it, it gets harder and harder to turn everytime I turn it off, to the point that it wont turn and has to be jumped. Had battery and alternator checked (autozone), they said the alternator was good and the battery was 100% but it wouldnt start unless I jumped it with a portable jumper, car sounded like the battery was dead. My car has a new starter solenoid but the wire coming from the key ignition switch looks pretty thin, its original, not sure if that could be the culprit. Any ideas?
You need a volt meter to diagnose this. Go buy a cheap digital meter. If the alternator is charging on the vehicle, close to 14.2 volts, then you have something creating resistance as it gets hot. The "only" way to find where the resistance is located on a large amperage circuit like a starter is to do a voltage drop test. You mar have a battery cable that is failing inside or a connector corroded on the cable or any number of spots where resistance could be hiding. Go on YouTube and look for videos on "voltage drop testing". You will need to understand the relationship between the voltage, resistance and amperage. This is actually a fun test to do and you will learn a lot. Its cheaper to go buy a meter than than replace perfectly good parts. Another thing you Cando is turn the headlights on when you crank it. If the battery is dead the headlights will go out. If there is excessive resistance blocking the amperage flow to the starter there will not be that much draw on the battery and the headlights will stay on. That is a quick way of determining if you have a battery problem or a starter problem when you don't have the meters to test the he different systems. I'm a retired ASE (double) Master Tech with 40-year's of experience, and I'm a vintage Ford guy. I have Mustangs, Falcons and hot rods...
 

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Hello I have a 65 2 door falcon, did an engine swap to a 302 5.0. Engine rebuilt and alternator, battery, starter, ignitions switch arte all new. Problem is I trickle charge the red top battery and the car fires right up at home everytime, but after driving it, it gets harder and harder to turn everytime I turn it off, to the point that it wont turn and has to be jumped. Had battery and alternator checked (autozone), they said the alternator was good and the battery was 100% but it wouldnt start unless I jumped it with a portable jumper, car sounded like the battery was dead. My car has a new starter solenoid but the wire coming from the key ignition switch looks pretty thin, its original, not sure if that could be the culprit. Any ideas?

When I bought my 65 Merc cyclone, I had a similar problem. Not as bad but my battery wouldn't hold a charge. I started poking around under the dash and found a wire connector that was always hot. It was one of those factory Ford female butt connections. Even though the plastic was intact it was leaking a little bit. I think they call this the parasitic drain.


If your engine still has factory wiring, you might have this same problem. Also, my oem style voltate regulator didn't work either. I got an electronic one and haven't had a battery problem since.
 

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Thank you for the reply. So I think we have it figured out. Red top battery swapped out for warranty and new starter cable. Seems to be working just fine now.
 
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