parasitic draw on battery

[AA-ron]

Hello everyone,
My car has been on the road for two summers and has about 6000 miles on it. Last week the battery died after the car sat for a two days. I charged it and all is good. Then the following day it was dead again. I tested it and I indeed have a parasitic draw... somewhere. I've diagnosed parasitic draws before in other cars and am familiar with the process. This one however has me baffled. Obviously it goes away when I flip the battery disconnect switch, but from there it gets really wonky. The draw is seemingly random. I'm testing at the negative terminal of the battery. Sometimes when I test it, it is at 25 milliamps-- which is good. Then I test it again and it jumps to 4.5 amps-- not good. I pull the prob away from the battery and reconnect it and it may still be at 4.5 amps but it also may go back to 25 milliamps. Then it may stay at 25 milliamps for repeated tests and then randomly jump to 4.5 amps.] It only changes when the test prob is removed from the connection and then reconnected. In other words, it is the connection and disconnection of power that is causing this random switch between current draw measurements. When it does read 4.5 amps, which is far less often, I clamped the meter in place and begin pulling fuses. I've disconnected every fuse including completely isolating the Sniper EFI, and have not found any circuit to make any difference. So looked at it differently and though ok, whats the only thing that is not fused, and it is the alternator and starter.
Do any of you know if there is something in either the alternator or starter that would draw 4-plus amps randomly? The alternator is charging as it should when the car is running.
I built this car and know the wiring inside and out, so I've chased down all the usual suspects (clean grounds, loose connections...etc)
Any help would be greatly appreciated.

Thanks!

[AA-ron]

I forgot to add that I tested it with two different meters and both read the same thing.

[Rebostar]

Ron
If you've pulled the fueses on all circuits except the starter and altinator, if you hav'nt done so already, I would suggest removing all the wires connected to the solinoid if its a remote solinoid. If it's a one wire Powermaster just disconnet the start lead and main power lead. If that dont help, try doing the same with the altinator, assuming you have a one wire unit.
Do you have any devices that required battery direct conections? Either POS or NEG. My E-Powersteeing requires a direct NEG conection to the battery. I have a master switch in my system that supplies a buss similar to an aircraft or boat. This helps prevent the "vampire" current draws.
Allyn

[Papa]

The only two things on my car that draw power when the car is off are the clock and the GPS gauge. The EFI computer may also draw power, but I'm not 100% sure on that. I wonder of the GPS gauge is doing something to refresh the data it needs to make satellite synchronization faster at random times? That might be an interesting question for SpeedHut.

[narly1]

The variability in draw could definitely be alternator related. There are diodes (aka rectifiers) inside that are used in the AC to DC voltage conversion process. If you are not familiar with these devices they act as a 1-way "check valve" to electrical current flow. So a bad (leaky) one could definitely be the cause.

Disconnect the alternator and see if the problem goes away. Note that you may have to watch your multimeter for a while to verify.

Earl

[narly1]

The only two things on my car that draw power when the car is off are the clock and the GPS gauge.

If either of those was drawing 4.5 A consistently there'd be magic smoke coming out of them. LOL!

Earl

[rich grsc]

Like Earl said, disconnect the alternator and retest.

[narly1]

Like Ear said, disconnect the alternator and retest.

The Ear is good, the Ear is wise, LOL.

Earl

[AA-ron]

Thanks for all the input. Yep, 4.5 amps is significant and it sounds as if its going to be the alternator. I'll check that tonight and report back.

[Nigel Allen]

12 volts @ 4.5 amps is nearly 60watts. Whatever is causing the draw, will likely be warm to the touch.

DC clamp meter would show the fault in no time and is non-invasive i.e. no need to disconnect any wiring.

Best of luck,

Nige

[rich grsc]

OOOPS, sorry Earl.
If I could type & spell, I'd be dangerous

[narly1]

OOOPS, sorry Earl.
If I could type & spell, I'd be dangerous

No worries you made me laugh and that's a good thing....along with the chance to yank your chain a bit LOL.

Earl

[narly1]

12 volts @ 4.5 amps is nearly 60watts. Whatever is causing the draw, will likely be warm to the touch.

DC clamp meter would show the fault in no time and is non-invasive i.e. no need to disconnect any wiring.

Best of luck,

Nige

I was thinking the same thing about the power....hence my comment about the magic smoke.

My bet stays on the alternator electronics being the culprit.

Earl

[Norm B]

Most likely the alternator. My brother’s GMC truck did the same thing. Battery kept randomly discharging. We had the battery charger hooked up overnight and went to check in the morning. Alternator was warm to the touch. New alternator fixed the issue.

[Mbufford]

Intermittent problems are the worst to troubleshoot. From your description, it sounds like you have an intermittent problem with the varying current draws.

Without putting my hands on it, the best advice I can give (as someone with many years of experience with electronic and electrical troubleshooting) is to: 1. Disconnect every system via fuse removal; let the car sit a few days and check the battery. That will tell you whether the problem lies in a fused or unfused system/component; 2. If the problem lies on the unfused end of the panel, disconnect all systems/components; 3. Once you know which side of the fuse panel the problem comes from, start reconnecting systems from that side and wait a few days between each until which one responsible for the phantom draw is found; 4. Depending on the system involved, it could be as simple as a chaffed wire or faulty internal circuit. But, until you’ve isolated the specific system at fault for the phantom drain, there’s no way for any of us to help troubleshoot beyond this type of general guidance.

[CraigS]

A reminder when you disconnect batt or alt, those cables are hot w/ full batt voltage and amperage. You might want to grab a 4-5" piece of heater hose or similar to slip over the end of the cable to assure it doesn't ground out while you are doing something else.

[narly1]

A reminder when you disconnect batt or alt, those cables are hot w/ full batt voltage and amperage. You might want to grab a 4-5" piece of heater hose or similar to slip over the end of the cable to assure it doesn't ground out while you are doing something else.

Or better (if possible) disconnect the cable connected to the suspect component/circuit at the battery end.

Earl

[MB750]

How specifically are you checking amp draw? What meter are you using, and how are you connecting it to the circuit?

I'd vote the alternator too. Back when I was putting my wiring together, I accidentally sent 12 VDC to excite the field regardless of the key position. It had a constant 3ish amp draw and took the battery out in a few days. When I figured out my snafu, that solved the problem.

Depending on your alternator, you might be able to swap out the regulator. But, test this first before throwing parts at it.

[AA-ron]

I spent some time on this last night and it figures that I couldn't get the problem to rear its ugly head. There was never more than a 25 milliamp draw. This is the problem, it's so random. This morning I reconnected the battery and tested it again and it went right to 4.5 amps-- and of course I need to go to work, so I couldn't spend any time on it. In both cases the engine was cold, so I can rule out warm versus hot variables. I might pick up a clamp on amp meter today to make testing easier-- probably should have one of those anyway.

[Nigel Allen]

If you buy a clamp meter, make sure it is for measuring DC, as some only do AC.

Cheers,

Nige

[TFary]

Unplug the alternator regulator

[MB750]

The best and most accurate amp meters are connected in series with the circuit. Voltmeters work in parallel. Inductance meters are ok, if you're out of range of a series wired meter.

[CraigS]

There may well be some but, as a dealer tech, the clamp on meters I had access to couldn't read in milliamps. You even need a fairly high end VOM to get milliamp scale.

[Nigel Allen]

There are inexpensive DC clamps that will measure to 10 mA. This is more resolution than needed for this task. It is possible to multiply the value of the reading by adding turns through the measuring clamp per video:

https://youtu.be/Zk0FyMJLio0?si=uoD6IpXWCQUPP_U7

I highlight using the DC clamp over an inline meter, as the OP mentioned breaking the circuit usually made the intermittent fault go away for some time.

Hopefully AAron is having some success.

Cheers,

Nige

[AA-ron]

Well still no luck getting the problem to show up again. I guess that is the very definition of "random". At no point during the weekend did the any draw show up in the system. Hot or cold made no difference. I'll continue to try to get it to happen and report back.

[Norm B]

Unplug the alternator.

Norm