I have a 2001 4.0 6 cyl and a few days ago I fixed my radio after finding out the antenna was unplugged on the back which is why all my stations were just static, I also should mention the lights on the screen starting to become dimmer and I had to give it a little love tap to brighten them up, and about two days later I go out in the morning to start my truck and it won’t start, nothing comes on, not a single light and there’s no noise, no ticking from the starter or anything… I get a jump and then replace my battery, everything is all good until the next morning and the truck won’t start again. This time, I have to give it some gas as well as the other guy trying to jump me in order for it to start up… I went to go get my battery, starter, and alternator tested today everything was good on the first test and then I did it again about 20min later with everything running, the ac and headlights on, and then the alternator tested a little low…

I’m being told it could be the alternator because the radio might have a short which is draining the alternator but I can’t afford a new alternator right now… I was advised to take out the radio for the day and try starting it up tonight and if it starts it means it’s the radio but if it doesn’t it means the alternator has gone bad…

I’m looking to sell the truck soon anyways as I’m moving across country and don’t have the finances to replace the alternator now as well, anyone have any financial friendly advice?

 

Clean the battery terminals, BOTH of them

Unhook battery when parked

 

Both terminals are clean and when I unhooked the battery when I’m parked with the truck running, it stayed on… that’s what confused my buddy even more, he said it has to be the radio which is why he had me uninstall it for the day and then told me to try starting it again later this evening, he said if it starts it’s the radio shorted out and if it doesn’t then it’s the alternator… this sound right?

 

No, it doesn't

And NEVER unhook battery with engine running, that was a VERY VERY old test used before electronics in cars and electronic voltage regulators
So do not do that on any vehicle made after 1980
Use a Volt meter
engine off battery should read 12.3v to 12.8v
engine running battery should read 13.5v to 14.8v, under 13.5v is bad alternator wiring or bad alternator

If Radio is draining battery then if you unhook one battery cable when parked, the battery won't be drained, so will start when you need it to
If battery still drains and no start then battery is bad, period, no other reason


Just to make it clear
Battery provides ALL voltage when engine is off, MAX voltage is 12.8v
Alternator provides ALL voltage when engine is running, 13.5v is MIN voltage

So Radio can not "drain alternator", it, or another electrical device, can drain Battery when key is OFF, unless battery is unhooked

Car battery's ONLY purpose is to start the engine................but it also acts as a buffer to absorb voltage SPIKES from alternator, spikes are very bad for new electronics(1980+), so if you unhook the battery with engine running and there is a SPIKE(which you can cause by unhooking the battery and hooking it back up) then say goodbye to some of your electrics, like the expensive engine computer
So just don't do it, a $10 volt meter is way cheaper, lol

 

That’s how my buddy tried testing it, hopefully it didn’t do too much damage for the short time he did it and only once at that…

And okay so in that case, like I put in the og post, he did run a test on it with a volt meter, with the engine off the battery was a little low, but mind you, I just replaced that a few days ago and I guess if the alternator is bad, it would drain it a little bit too… But with the engine running the alternator read about 13 and the battery was a little low and so is my guess, then when I turned the lights and ac on the voltage on alternator dropped to 10

 

Alternators minimum voltage, engine running, should be 13.5v, so its not working

You have a volt meter, I assume

So engine off, key OFF
Test battery volts, lets say 12.1v, because you said its low, but what ever it is REMEMBER IT

Now use volt meter to test alternator wires
On the back of alternator is a stud/nut terminal, called B+
Test it for voltage, should be Battery Volts<<<<what you remembered
If not then Fusible links are blown, need to be replaced

Unplug 3 wire connector on alternator
Test the Yellow wire, should be Battery Volts
If not more than 1 fusible link is blown, replace them

If B+ and Yellow wire are both OK, Battery volts
Then plug back in the 3 wire connector, and make sure the White wire jumper is also plugged in to its single terminal connector on alternator

Turn on key
Battery Light on dash should be ON, if not check and replace fuse 11 in cab fuse box, its blown, 7.5amp fuse
Battery light is the ON/OFF switch for alternator

If battery light comes on, start engine
Test battery volts, should be 13.5v to 14.8v
If under 13.5v then alternator is bad, period



Fusible links are short wires that are made of a softer metal and insulation that melts without catching fire, they are in essence "slow blow fuses" but cheaper, lol
These will be located on the battery connection for the alternator wiring harness, NOT at the alternator end of the wires
They will be inside the harness's wrapping so you will need to unwrap the wires to get too them, if they need to be replaced
Examples of fusible links seen here: https://ceautoelectricsupply.com/product/fusible-links/

Any auto parts stores have these
2001 Ranger uses 2 12gauge and 1 18gauge link