I’ve got one, and I have tried to track it down a couple of times with no avail. Anyone have some time this coming weekend to help a brother out?
Anyone good at tracking down parasitic drains?
- Thread starter damon
- Start date
What all have you tried? How much draw? Unfortunately I don’t have time, but I’ve tracked down quite a few over various platforms over the years.
Maybe a bit of discussion here could help?
Here are the culprits I’ve found most often in order and few odd balls.
- After market accessories, usually stereo’s (Amps), remote starts, CB, HAM etc
- Dirty filthy nasty battery/terminals
- Bad Power door lock ECU
- Bad Alternator
- Bad ABS module
Inukshuk
Rising Sun Member
What Jackson said plus:
Which truck?
I have a DC clamp meter that may help.
Which truck?
I have a DC clamp meter that may help.
Do you still have a factory alarm?
DanInDenver
Trail Ready
I've read recently to test each fuse with a volt meter to try to find the draw source. Replacing my alternator this week and if that doesn't fix my issue I'll probably also be looking for a parasite.
this is in the 80. I have tried pulling fuses and looking for a drop in the draw, pulling accessories that aren't though the main fuse box, pulled the factory alarm out, and other things at aren't coming to mind. I don't recall what the draw was, it's been a while since I last did it.
I’d start by pulling the ground cable and checking the overall draw (measuring from Batt to Ground in series). Then start one by one pulling wires that are attached to positive. That will help identify weather it’s an added circuit or a factory circuit.
As long as you don’t believe the draw to exceed the current capacity of your meter.
As long as you don’t believe the draw to exceed the current capacity of your meter.
Inukshuk
Rising Sun Member
I have an inline meter good to 10A. My clamp meter goes far higher.
Pulling fuses till draw disappears or testing each with A meter is a great idea
Pulling fuses till draw disappears or testing each with A meter is a great idea
DaveInDenver
Rising Sun Ham Guru
In judging how bad a parasitic is you first need to make sure you have a problem at all.
The normal threshold for "excessive" in anything with an ECU or electronics is 50mA constant draw. But a mid 1990s Toyota should be around half of that, say 25mA or so, before you can really say you're tracking down more than normal.
A 92 A-hr battery in absolutely new condition and starting fully charged with a 25mA load will in theory reach 0% in 3680 hours, about 150 days. But for most batteries that are in the middle of their life and not starting from 100% (Toyotas chronically under charge) it'll be much less. Plus, that's only supplying the constant load. Being able to start after a period of sitting is not nearly as long. You need something in the tank to crank the starter, so even ideal battery at 25mA you can only take so much.
So for most of us just driving and parking our truck that isn't an FJ40 or 20R mini a month is about all you can count on under perfect conditions, a week or two in the middle of winter could be a marginal battery.
Another question is whether this happens in the summer, too, or just winter? A battery at 32°F can only source 60% of the current that it can at 75°F. Then when it gets really cold, at 0°F a battery can only get you 20% of its rating.
Now taking that a step further, what criteria are you using to say you have a parasitic? Not being able to start or just battery voltage? Are you sure your battery isn't just tired?
The normal threshold for "excessive" in anything with an ECU or electronics is 50mA constant draw. But a mid 1990s Toyota should be around half of that, say 25mA or so, before you can really say you're tracking down more than normal.
A 92 A-hr battery in absolutely new condition and starting fully charged with a 25mA load will in theory reach 0% in 3680 hours, about 150 days. But for most batteries that are in the middle of their life and not starting from 100% (Toyotas chronically under charge) it'll be much less. Plus, that's only supplying the constant load. Being able to start after a period of sitting is not nearly as long. You need something in the tank to crank the starter, so even ideal battery at 25mA you can only take so much.
So for most of us just driving and parking our truck that isn't an FJ40 or 20R mini a month is about all you can count on under perfect conditions, a week or two in the middle of winter could be a marginal battery.
Another question is whether this happens in the summer, too, or just winter? A battery at 32°F can only source 60% of the current that it can at 75°F. Then when it gets really cold, at 0°F a battery can only get you 20% of its rating.
Now taking that a step further, what criteria are you using to say you have a parasitic? Not being able to start or just battery voltage? Are you sure your battery isn't just tired?
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One easy test to kinda confirm what Dave's talking about would be to disconnect your battery entirely.. like if your truck is dead 3 days after drive it, then ok go drive it and then disconnect the battery. Come back in 3 days and hook it up again...
And my experience has been 100% of the time when there's been a drain/draw/battery issue it's been something that I added, not factory. like a cig lighter plug hooked to a fridge that's not even turned on.
And my experience has been 100% of the time when there's been a drain/draw/battery issue it's been something that I added, not factory. like a cig lighter plug hooked to a fridge that's not even turned on.
I hear ya. If I trickle charge the battery back to 12.7v, it is usually down to 11.9 within a few days. Then I repeat the process. I had a battery that cratered about a year ago, replaced it 6 months later with a warranty swap (Costco Interstate), then late last week replaced with an X2 Power AGM.
I'll run outside later and get a new reading for the resting mA drain. Maybe I am just crazy?
60wag
Rising Sun Member
- Joined
- Aug 23, 2005
- Messages
- 2,476
I've got almost the same situation going on on my 80. I thought the battery was old and weak so I replaced it. Still drops to 11.9ish in a week after sitting on the charger. No AGMs involved, just flooded lead acid. Haven't had a chance to dig into it yet. My plan is to put an amp meter on it and start pulling fuses to try to locate it.
DaveInDenver
Rising Sun Ham Guru
To give context to Damon's concern this is a generalized State of Charge (SoC) chart that relates voltage to condition. It's more accurate to measure current going in and out of a battery to know but voltage is close enough and of course much easier.
For the purposes an X2 is the same as an Odyssey and most regular AGM are like flooded.
So dropping that fast from 12.7 -> 11.9 is very likely indicating a problem. But maybe not.
I will mention that X2/Odyssey are tough to charge and Toyota does them no favors (notice that most of our trucks struggle to put an Odyssey no better than 80% SoC). Doing the diode trick to bump voltage fixes one issue but creates another in over charging. I had better luck leaving things stock to prevent getting them too hot in the summer and routinely putting a good charge on them from a shore charger.
That being a PITA, I just went back to a cheap (and thus replaceable more frequently) flooded for my starter. I've had better luck using an X2 for a house battery but that sits on a Victron DC-DC charger all the time so gets better handling.
It's also important to factor in temperature. Remember I mentioned capacity is rated at 25°C. At 0°C you have about 60% of rated and at -20°C about 20%. The open circuit measurement might show 12.7V but if the battery is cold as soon as you put a load on it will drop. Some of these tests and parameters thus require that you either adjust for conditions or take the battery inside a heated space.
Also keep in mind that in the end it's about the battery's ability to source current. Voltage may not fully indicate condition. You need enough voltage to push the current that the starter and whatever electronics require. You will see a brand new battery dip to around 10V or 11V when starting and that's completely normal and Cold Cranking is based on current delivered for 30 seconds until the battery hits 7.2V.
On the flip side don't get complacent that a higher voltage automatically indicates a good battery. It's what happens under load, e.g. current and time, that matters. A battery that's in good shape but in need of a charge might show 12.5V while a battery that is at the end of its life might show 12.8V but as soon as you bleed off the surface charge it's got nuthin' left.
If you can record voltage while cranking if it begins at 11.9V but only drops relatively little then it could be just normal and the battery is OK and parasitic drains aren't taking an abnormal toll. Might benefit from being charged and conditioned with something plugged into the wall, still.
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I had a parasitic draw in my 80 for a while that I fixed. It was the factory amplifier that was used with the original head unit. I had replaced the head unit within a day of buying my 80 back in 2004, but the old factory amp was still there behind the dashboard, drawing power. It's behind the dash on the passenger (right) side. You can simply unplug it to see if it fixes the problem. I eventually completely removed it.
I pulled mine back when I put in a new headunit. Good call tho!
so you replaced your AGM with something else?
C.Gerdo
Rock Stacker
- Joined
- Feb 25, 2023
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- 34
I went back to a standard flooded lead acid.
What I have experienced is, AGM tend to instantly go from good to bad. Almost like one cell just dies. More of a chance of getting stranded. Flooded lead acid tend to get weak at the end of their life. The vehicle starts cranking slower. A good warning sign to replace.
What I have experienced is, AGM tend to instantly go from good to bad. Almost like one cell just dies. More of a chance of getting stranded. Flooded lead acid tend to get weak at the end of their life. The vehicle starts cranking slower. A good warning sign to replace.
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