Where me with problems

[MaicoDoug]

Momo,
The best way to test any circuit in a vehicle of the age we are discussing for a battery being drawn down is to first disconnect the battery alone and watch it over night. Don't leave the meter connected. Often the battery will have a shorted cell and draw itself down disconnected. Once that test, issue has ruled out a good or bad battery, you can proceed.....

On your meter, leave the black wire where it is (COM) on your digital multimeter (DMM), and plug in the red probe to (10A) hole. Disconnect your battery's negative cable. Connect each meter probe (doesn't matter which wire goes where), one probe to the neg battery post & the other one to the neg cable you just took off. Connect them well enough to not have any intermittent connections. DON'T start the motor, Don't turn anything on. The meter is now showing your parasitic draw. If you have any. If you see something, it will be for sure the dome (door) light if the door is open. I would pull that light and get past that issue first. Then you can start pulling fuses one at a time.

If it shows any value displayed, then you have something still connected and potentially drawing down the battery. Start unplugging the fuses if a value is displayed. One at a time. Remember, do not turn ANYTHING on. You will likely blow the internal 10A fuse inside your meter. Plus the probe wires will not pass 10A for very long. Pull one fuse at a time while taking a video, pictures for a record of what fuse goes where. Do not replace the fuses with the battery's negative cable replaced and connected, or when the meter still connected during this test. Funny things sometimes happen like the ECM restarting. Stuff restarts when the key is in the OFF position. Do yourself a favor and replace the fuses one at a time with the battery/ meter fully disconnected. Pull one of the meter probe wires off each time to replace each fuse, having a friend helps. This way the ECM can't know anything except that the battery was disconnected, and the fuses will know where they came from. Cycling those connections also helps keep old connections healthy.

Good luck & let us know how it went.

Remember were attempting to discover any unexpected parallel loading across the (+) & (-) wires, not bad or intermittent series connections. Those won't draw down a battery. They simply don't deliver voltage well when turned on & energized.

 

[Momohenri]

Thanks for the advice; I've already done the test with all the fuses under the dashboard and there was nothing wrong. There are no fuses in the engine compartment, only fusible links, so if it's at the engine level, I don't know how to test it.

 

[MaicoDoug]

Do the battery test disconnected. I believe you have a bad battery, and also look for 13.8v when running at the battery posts, more than the 12.6 resting when the motor is off. That fusible link (one of a few) may be responsible for the charging problem.

Fusible links are for a series connection. If your battery is being drawn down, 99% it's not from a bad connection. It's something turned on. Do the test with the battery disconnected and left alone.

12.6v should be 12.6v after 8 hours. Know the difference of a parallel & series circuit. A fusible link delivers voltage, (serries) only when that system is turned on. Never when it's turned off. The charging system is where I believe your issue may indeed be. Look for that higher voltage when the engine is running.

 

[Momohenri]

Every day, I disconnect the battery, I have no choice otherwise I no longer have enough energy to start, if I disconnect it it has the same voltage as when I stop it, it does not come from the battery which is only two months old

 

[MaicoDoug]

What is your charging voltage, battery terminal voltage when it's running?

>The battery is 2 months old.
>You must disconnect the battery each night to have enough to start each morning.
>The truck passed the parasitic draw test with no current being drawn.
Q: With the motor running, what is the battery terminal voltage?

 

[Momohenri]

when the engine is running I have about 14.5 V, when stopped about 12.6 V

 

[Mechrick]

You could have a shorted diode in the alternator. Look for a tiny spark when disconnecting/reconnecting the battery, then disconnect and tape the B+ wire at the alternator (the big wire) and see if the spark goes away at the battery terminal.

 

[Momohenri]

ok, i'll try that tomorrow, it's getting late here

 

[MaicoDoug]

With the pot metal quality battery connectors these days, current draw required from the starter will be passed, but because of the quality of metal may be dropping that extra volt needed to charge the battery. I have a habit of checking the post voltage & then the battery lug voltage looking for a bad connection. Like Meckrick says, I'm also interested to know that your alternator is operating properly.

With charging issues, it is very common to suspect everything. Cables, battery, charging systems including fusible links. Voltage drops across small (charging) wires only when current is drawn. I can show you a case study where a resistor drops no voltage until you start pulling current from it. Then the voltage plummets and then you got no charging voltage.

 

[Momohenri]

Some news, I tested by disconnecting the ground cable from the battery, put a friend's multimeter between this wire and the negative terminal of the battery and I get between 7.3 and 7.6 V which seems enormous to me for a loss, my multimeter gave nothing so it is not good.
Then I reconnected the negative wire and started the engine, at first I had 13.7 at the battery which is low and it started to drop by a tenth at a time, after about 1 minute I was only at 12.9 V so I think my alternator is dead. Before the engine started running, I did the KOEO test and it gave me 10 and 11 so it was ok, once the engine was running I did the KOER test, it gave me 6 (that's for the number of cylinders) and then nothing, the little square on the tester stopped flashing!!
Any ideas?

 

[MaicoDoug]

Momo, wrong test. You're measuring voltage. YOU NEED to measure current, as I said, use the "10 A" hole on the multimeter to measure CURRENT, not VOLTAGE. That is a (cut the connection & insert a current passing device such as a current meter) series test. You need to also test for current drain like you did with the negative cable removed, but you did not have the meter in the "10A" mode. Try it again exactly as I described. That is the only way I can help you. Sorry to repeat myself. Good luck. & remember I mentioned to educate yourself regarding "parallel & series" circuits. Series for current, parallel for voltage.

12.6 volts is charged by a 13.8volt supply causing power to flow from the 13.8v alternator to the 12.6v battery. You must insert a current meter measuring AMPS in series between those two components to see that flow but that is not the drain test, this is another "current test. The typical battery charging current if everything is ok just before shutting off a fully charged battery is apx 4 amps. A couple minutes just after starting is about 8-10 amps, FYI.

Most people that have these symptoms simply throw parts at the problem like I mentioned before. Knowing exactly what is happening such as the drain test needs to be done looking at current using a current meter. The voltage test as I have already mentioned is preformed by looking for the differential voltage (12.6/13.8). It is assumed that that difference in those voltages is using a working system (and related components, cables & connections) to send the current to the battery as with any charging system. Just because the alternator has a higher voltage does not mean it will make it to the battery posts of a new battery. Good luck.

 

[Momohenri]

Thanks for the replies. I understood that you had to look for amperes and not voltage, but for some reason, the ampere test doesn't work on my multimeter or my friend's.
Another weird thing, a few days ago when I was doing a voltage test with the engine running, I had 14.5 V, now at the beginning I have 13.7 and after a minute 12.9.
As I said, I have a loss between 7.3 and 7.6 V with the battery disconnected at the negative and multimeter between wire and negative terminal, if I disconnect the B/Orange wire the multimeter no longer indicates anything.

 

[Mechrick]

Multimeters have a very high input resistance on the V setting, and a very low input resistance on the current setting. The vehicle's normal voltage draw to power up the PCM's backup circuits will cause a DVOM to read volts with the test you performed even when there is nothing wrong.

By orange wire, do you mean at the alternator?

 

[Momohenri]

yes the Black/orange who come from the alternator

 

[Mechrick]

With the key off, there should be no current flow through that wire. If there is, the alternator is bad...