Searching for battery drain

Hello everyone. Thanks to members here I learned to successfully pull out my driveshaft and replace the u-joints and carrier bearing. This community is a great resource and I'm grateful to those who contribute! Now I'm on to the next issue:

It seems that something is draining my battery while the truck is parked and off, which led to some slow starts and finally jump starting. As a stopgap solution I began disconnecting the positive cable from the battery when parked. At the time my battery was 8 years old so I went ahead and replaced it. The issue is still there with the brand new battery, so I can eliminate that. I am familiar with troubleshooting and repairing appliances with a multi-meter, so I thought I'd try testing circuits in the fusebox for continuity.

With the ignition OFF and the battery disconnected, I removed fuses one at a time and checked for continuity by touching a probe to each female contact for the removed fuse. There was no continuity in any circuit until I got to the headlights. When I remove a headlight fuse and touch the probes to the female connections there IS continuity. When I touch one probe to one female headlight connection and the other probe to the engine block there is also continuity; this is the case no matter which one of the two female contacts I touch. All light controls in the cab are turned off as well.

Is there a reason why there should be continuity in the headlight circuit or is this an indication of a short?

 

Try a parasitic drain test

https://www.youtube.com/watch?v=iNEpCqcxImU

 

Thanks! I'll check that out. -B

 

It’s going to be virtually impossible to find a power drain with no power. Start by reinstalling all the fuses, and connecting the battery. You will need a DVOM with the a fused, 10 amp function.

start by connecting the DVOM to you battery on the negative side and measuring the draw. Now, with aid of a helper, do all the easy stuff. Start by ensuring EVERYTHING Is off. Turn things on and off, open and close doors, etc, making sure each time that you return each control to the off position. The helper will monitor the meter a d let you know if it returns to the same valise as before.

Assuming it’s nothing easy, next start removing the fuses one by one. Note which one eliminates the current draw and concentrate on that circuit.

 

https://youtu.be/6xFo_oHFF48 This guy is a great teacher . I always use the old faithful method.

 

How long a time period 8to 10 hours less then or more 48 hours ??

 

I watched both videos you guys posted; thank you. I connected my multimeter in-line, on the negative side of the battery, on the 10amp test setting as described in both videos:




With the ignition switch off, the doors closed and all other switches turned off, there was a steady reading of .14 on the multimeter:




I then went through the interior fuse box, removing each fuse one at a time and the meter stayed at .14.

Then I went through the fuse box in the engine compartment removing each fuse one by one. The only fuse that made a difference in the reading was the dome light fuse. When I remove that fuse the draw drops to .00 on the meter. Yes, the dome light was set to OFF and the door was closed. I tried it multiple times and got the same result, so I appear to be making progress:



Since the sun just set I removed the dome light fuse for now. I need to do a little research into that circuit to figure out how I'll find the short. In the meantime, I'll wait and see if this makes a difference with my slow start problem in the morning. I'll add more to this thread when I make more progress. Thanks again for any and all advice that's been offered! -B

 

Dome light fuse is also used for the radio presets and the clock it will always have a current draw

Disconnect the radio and clock see what happens.

 

Sounds like a bad cell in your battery .
Even though your battery shows over 12 volts , its the cranking amps that will create a slow start in the morning .
A lot of places will load test for free .
May I suggest a battery load test ?

 

Except that he put a brand new battery in it with same result, and testing (posted above) seems to indicate a dome light circuit issue.

 

You are correct . I missed the new battery statement somehow LOL
Not the first time I have seen a new battery with a bad cell mind you .

 

totally. or there's an issue like a short or something that ruins a new battery.

 

Any luck?

 

I did this once and found similar results.. about a 150mA parasitic draw when the truck was off. It's high by modern standards, but a good battery should be able to go a couple weeks and still start your truck.

I would consider your starter and/or the wiring to it. Sounds like a little voltage boost is all it takes to get it going.

 

Agree. Dirty contacts in starter solonoid. That’s peanuts for voltage draw on a battery that large. Sure, sooner or later it will be dead but certainly not overnight

 

While 140mA is high enough to count as 'something's wrong' it won't kill your battery overnight. In fact it should still be able to start the car after 2 weeks of sitting. Most modern cars, and the 1st gen taco ain't, will have 60-100mA as a normal parasitic load. On older cars like the 1st gen taco you should see parasitic draw around 20-30mA.

 

140mA draw for 24 hours would only be 3.36 Amp-Hours, and for 2 weeks would be 47.04 Amp-Hours. A new battery should have at least 50 Amp-Hours and probably more, so yeah, it shouldn't drain the battery in just a day or 2.

Instead of concluding the battery is dead based on cranking the engine you should measure the voltage directly at the battery posts. Maybe you just have a corroded start cable or bad connection somewhere.

Is it possible something is turning on or left on? Interior light? The brake lights can get stuck on if the rubber cushion on the brake pedal breaks apart. Maybe the radio comes on. Or do you have a scan gauge that you leave plugged in or something plugged into the cigarette lighter?

 

My trucks battery was being drained after doing a redneck sub install. I fixed it, but check anything you may have installed in radio wise, as someone else said your radio is for some reason interacting with the dome light fuse.

 

Op have you pulled the dome light bulb yet? start with the easy stuff first so many times have I seen a car roll in(never a taco) with a parasitic draw and ended up being blown bulb that was out for so long that it began shorting and causing the draw.

 

Having this same issue. Since COVID started and we got my wife a Jeep, we have not been using the truck as a DD - only about 3000 miles in 12 months only. if it sits for a week or more the battery is stone dead. I replaced the battery - same issue. Today after jumping it, I pulled the fuse on the heated seats (aftermarket) to see if that might be it. The only other "mods" are the upgraded head unit, remote starter, and the towing package with brake. But all those things were there long before the problem started. I am flummoxed as to why this is happening now. I guess i need to get an ampmeter and start pulling fuses to see what is causing it.