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Draining battery problem. Diagnosing not going as expected.
A couple of weeks ago, I came out to a dead truck. One click and done. No radio. Dim dome light. I thought I had left the dome light on, so I chalked the problem up to my mistake and bought a new battery. The truck started, and everything seemed normal again.
This is a second vehicle, so it sat for four days. I went out to start the truck again, and again the vehicle was dead. No click, no radio, no dome light.
When I got time this weekend, I took the battery back to the store and had it charged. According to the parts store guy, it charged OK and passed the test. I put it back into the truck (negative disconnected) so that I could perform a parasitic amp draw test like in this video
When I connected the DVOM to measure the amp draw, the reading was zero. Strange. I checked the volts, and the reading was 12.8. I connected the negative terminal and tried to start the truck. One click and then nothing.
Now I'm stuck. I don't know what to check or try. Could the battery read 12.8 volts but still not have the juice to turn over the engine?
I have AAA, so I could have it towed to a shop, but I'd rather try to fix it myself. Any help would be appreciated.
How are your cables and connections? Have you checked the grounds? Sounds like an issue with the solenoid or the starter. I always have a spare stater solenoid in my '72 and you can try tapping on the starter to see if she will unstick and crank over. You've got enough juice to crank.
I made the battery connections more secure, and the truck does turn over now. Now I just need to find out why I can't get any amperage reading on the two different meters I am using, so that I can figure out why two batteries drained.
I have found that using a test light works the best for me. Disconnect the negative cable as before and put the light between the negative cable and the negative battery post. The light will cone on and energize any circuits that need some current and then go out. If the light stays on, then there is a draw somewhere. You can leave the light hooked up and then start pulling fuses or disconnecting components until you get the light to go out. If you place the light were you can see it easily, you can work in the cab and lookup to check the light status.
Take your time and good luck.
Most multi-meters do not have a large enough fuse in them to actually crank the truck while you are performing a parasitic current draw test. I wasn't for sure that you disconnected the meter before trying to crank.
I use a battery disconnect from a boating supply store when I perform a current draw. I place it on the battery terminal and the battery cable. I close the switch if I want to do anything with the truck, open a door, start etc. Anything that could cause an amperage draw greater than the fuse in the meter. Once i've got everything setup, I connect the meter across the battery disconnect and then open the switch (disconnect) so all amperage runs through the meter. Remember, if I have to do anything to create an amperage draw, I close the disconnect to protect the meter's fuse.
Once I've got the meter reading, I start pulling fuses and see which circuit has the draw. If it doesn't go away with the fuses, I start looking at other things and unplugging items like the alternator, etc.
Are you sure you have your meter's connections in the correct holes for checking current?
I had the negative cable disconnected. One multi-meter lead was touched to the negative battery terminal, and the other multi-meter lead was touched to the disconnected battery cable, thus closing the open circuit.
I did not crank the truck while the multi-meter was in series. I connected the negative battery cable and cranked the truck to verify that the battery had enough charge. The truck did crank, so I determined that the battery had enough charge to successfully perform the amperage measurement. I then disconnected the negative battery cable, and placed the multi-meter in series as described in the above paragraph.
In this configuration I wasn't able to measure any current. From what I have learned, a vehicle will have a slight amount of current draw, even with the doors closed, key out, radio and lights off, etc. I didn't see even the 50 milliamps I expected to see from what had been mentioned in the demonstration videos. So that's where I stopped. I thought that maybe there was a problem with the multi-meter I was using, but I wasn't sure.
You did the test properly. Dunno why there was a suggestion of cranking the starter while connecting with an ammeter. Cranking is NOT a "parasitic" draw. You're looking for a draw that's there when you expect everything (except the PCM and radio memory) to be off. So yes, your procedure is correct. Two questions remain: Are you starting with the meter on the lowest range setting? And do you have some other way to test the DC amperes function of the meter? Another vehicle, perhaps? (Oh, and you're setting the meter to DC current, not AC current, right?)
Another "sanity check" test - connect your meter up as described, and open the door. The dome light / courtesy lights should def. show on the ammeter.
it is also possible the ampmeter side of the meter is bad.
it mat read volts and ohms, but not amps because there is a small fuse in the meter to protect it.
During a crank test we can observe the battery voltage across the terminals. A fully charged maintenance free battery at rest, surface charge removed measures 12.8 volts.
You asked if it's possible for the battery to measure 12.8 and not have enough juice to crank the engine. The answer is yes. This is the exact principle behind a "load test" and we can perform a kind of load test while cranking the engine over with the ignition disabled.
It depends on the temperature, and battery health what the exact cranking voltage is acceptable but as a general rule the cranking voltage must never drop below 9.5 volts. As a field test turning on the headlights is a practical way to see if the battery can provide current. Also observe whether the lights go out during cranking or stay bright.
After all this, it's often usually a matter of loose, missing, or corroded cables and connections at block, frame, and firewall.
to measure the amps drawn by a starter during crank, can't do it with a basic DVOM.
Measure parasitic draw in series yea but not the amperage drawn during engine crank, as stated if try it with it connected in "series" it would instantly display "OL" giving no result. If it didn't the little probe leads would melt down!
If everything as it should be, system in good working order, starter would draw around 50amps give or take a couple for the brief moment it'd take to start one.
I had the negative cable disconnected. One multi-meter lead was touched to the negative battery terminal, and the other multi-meter lead was touched to the disconnected battery cable, thus closing the open circuit.
In this configuration I wasn't able to measure any current. From what I have learned, a vehicle will have a slight amount of current draw, even with the doors closed, key out, radio and lights off, etc. I didn't see even the 50 milliamps I expected to see from what had been mentioned in the demonstration videos. So that's where I stopped. I thought that maybe there was a problem with the multi-meter I was using, but I wasn't sure.
I meant that most multi-meters have a separate port you have to put one of the leads in to do current measurement. Make sure you had the leads in the correct ports.
Most meters I've seen have a separate port for the POSITIVE lead for DC current up to 10 amperes. But they typically also will read up to 100 mA on the "main" positive lead.
The OP does not want to measure current draw while cranking. When the battery is charged, the starter cranks and starts the engine just fine. The OP is looking for a PARASITIC draw, one that is draining the battery while it's parked.
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Draining battery problem. Diagnosing not going as expected.
