Won’t start no noise.

[aj81spider]

Something to consider if the battery is discharging when it sits. The most common replacement switches actually leave one of the switched power outputs on all the time (this happened on my car). The drain from that depletes the battery within a short period - for me it was a few days to a week - to where it won't start.

For several years I used a battery disconnect on the battery terminal in the trunk to disconnect the battery when I wasn't using the car. This year I finally put relays in the car and got everything off the switch (and drove the relays with the switched output), although I still disconnect the battery when not using the car out of habit.

[vincefiat]

Something to consider if the battery is discharging when it sits. The most common replacement switches actually leave one of the switched power outputs on all the time (this happened on my car). The drain from that depletes the battery within a short period - for me it was a few days to a week - to where it won't start.

For several years I used a battery disconnect on the battery terminal in the trunk to disconnect the battery when I wasn't using the car. This year I finally put relays in the car and got everything off the switch (and drove the relays with the switched output), although I still disconnect the battery when not using the car out of habit.

Thank You, can you give me more details. New to this stuff and not to technical but would like to look into it if possible.

[spider2081]

I agree with DieselSpider if the battery is not fully charged the alternator will not be putting out 13.8 volts at idle. Most alternators begin to function when they are rotating around 1000 rpm. This is not necessarily the same as engine RPM. A dead battery can be asking the alternator for more current than it can produce at low RPM.

Have you disconnected the battery terminals and cleaned them.
Have you checked the terminals on the starter solenoid? are they clean and tight
Have you checked the ignition switch 6 cavity connector??
Have you checked the single bullet connectors used in the brown and the red wires near the bottom of the charcoal canister behind the alternator?
Have you inspected the main chassis ground that attaches to the transmission bell housing?

All of the above are normal electrical maintenance item. Just like checking the engine oil.

[aj81spider]

Here is the type of battery disconnect I put on the car. It's the quickest, simplest solution to making sure there is no battery drain when the car is parked and it has the advantage of allowing you to quickly disconnect the battery when working on the car - pulling off the cable is enough of a pain that I'm tempted not to do it sometimes - with this there is no excuse.

https://www.amazon.com/Battery-Terminal ... s9dHJ1ZQ==

You can get these types of disconnects at auto parts stores as well.

The ignition switch I had left power on the INT output of the switch all the time. This is supposed to be switched on the Fiat ignition switch. That created about 1/2 an amp of current draw (I measured) when the car was parked - 1/2 an amp will drain a battery pretty quickly.

I agree with the comments above that 13.1 is too low for the alternator in normal conditions. I would fully charge the battery, then check the alternator output with the fully charged battery. You can also have someone rev the engine gently to see if the voltage changes when at 2 or 3000 RPM (after the battery is charged).

If it's really a new battery and it dropped enough to not be able to start the car there are only two options - the alternator isn't recharging it or you have a current draw when the car is off. If you're getting 13.1 out of the alternator then the alternator is at least powering the car when you're running, so I'd put my money on the battery being drained when you are parked. The switch above will prevent that (and buy a battery charger for the inevitable times you forget to disconnect after a ride ... ask me how I know that happens).

[SteinOnkel]

A decent way to find the mystery current draw is to set your voltmeter to amps and connect it in series to your battery negative and chassis ground. Then you pull fuses one by one until the voltmeter reads 0. Once it drops, you've found the circuit that's constantly drawing.

Won't work for unfused circuits though.

[vincefiat]

A decent way to find the mystery current draw is to set your voltmeter to amps and connect it in series to your battery negative and chassis ground. Then you pull fuses one by one until the voltmeter reads 0. Once it drops, you've found the circuit that's constantly drawing.

Won't work for unfused circuits though.

Good idea, will work on it this weekend