So I disconnected the neg battery lead … put my digital multi on amps .. touched pos lead to neg battery post and it’s zero-d out … I must be doing something wrong bec I do have some drain happening.
Parasitic battery drain test
- Thread starter Kschep
- Start date
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With the negative meter lead on the earth cable, and the meter leads in the correct holes in the meter presumably?
Have you checked that your ammmeter fuse isn't blown?
It's quite a common thing to accidentally leave it on amps and blow the fuse by testing for volts...
Have you checked that your ammmeter fuse isn't blown?
It's quite a common thing to accidentally leave it on amps and blow the fuse by testing for volts...
DeskJock
SILVER Star
Batteries will always have some discharge even if not connected or in use.
If you have disconnected your battery can test and then retest in 24 hours - if the voltage change is significant- you have a bad battery.
If you have disconnected your battery can test and then retest in 24 hours - if the voltage change is significant- you have a bad battery.
pb4ugo
SILVER Star
I usually do that test using volts. Check batt voltage, then test red lead to neg cable blk lead to neg batt post and compare the two. If there's a draw then start pulling fuses until it stops.
DeskJock
SILVER Star
I still have the factory amp meter. If is on - I know it.
- Thread starter
- #6
That’s exactly what I was trying to do
- Thread starter
- #7
Ya the fuse is good - let me take a pic of exactly what I’m doing
This may not always be true depending on your specific vehicle. I had a paratisitc drain after installing a NOS 80 amp fj40 alternator on my 40 a couple years back. The diode on the NOS alternator was bad and there was a very minor intermittent parasitic drain that I couldnt track down through any of the fused circuits. It drove me nuts until I replaced the alternator on a hunch - that was the fix for me. Because the new alt was internally regulated and connected straight to the battery, chasing down amperage through each fused circuit didnt reveal the issue.
- Thread starter
- #9
Ok here is the set up of what I’m doing. Again I’m just trying to ID where the parasitic drain is. If any (but there has to be bec if I leave it in the garage for one full day & night, it’s drained).
- Thread starter
- #10
Oh s*** - when I switch it to mAMPs and touch to neg post - a fricken noise happens down by my starter I think? I dunno but I didn’t wanna do it again for fear of messing something up.
Here’s the set up when I did that..
Here’s the set up when I did that..
Does it start properly ? Have you looked at the back of starter to see if wires are loose/whatever ? Next up would be the ign switch as IIRC all main power goes thru it so if something is still hot it may not be disconnecting the circuit.
The pos lead at 10A and the dial to 10 is the correct config for testing like you are - in line testing. In this pic you have it set for testing across the individual fuses.
Did you do a voltage test or fully charge your battery before trying this? If the battery checks out and is fully charged but is draining within a day, you should definitely see something on your multimeter.
Did you test your multimeter? Set it to OHMs and cross short the leads. You should see like .1 or .2. Def not 1.
There are a bunch of circuits which should have power without the ignition on.
Weird that you're reading zero though if you're draining a battery at maybe 2A.
Your mA fuse is only 200mA, so if this is still intact then seems strange.
Maybe you're ignition switch has an internal weak short at the start position - try unplugging it overnight?
Or.. hook up the battery for 20 mins and feel to see if the solenoid gets warm
Weird that you're reading zero though if you're draining a battery at maybe 2A.
Your mA fuse is only 200mA, so if this is still intact then seems strange.
Maybe you're ignition switch has an internal weak short at the start position - try unplugging it overnight?
Or.. hook up the battery for 20 mins and feel to see if the solenoid gets warm
- Thread starter
- #14
pb4ugo
SILVER Star
Is that reading with the batt disconnected? What's the voltage with the meters red lead on the disconnected neg batt cable and the black lead on the neg batt post?
brooklyn
SILVER Star
My first question to myself when things like this happens is what did I touch just before the problem started! For next steps, I would get the battery tested. Also, I had Optima batteries for years and always had problems with dead or low charge. Finally bought the best battery I could from auto zone and never had a problem since. If you have another car, swap the battery out and leave it in overnight to see if the battery is an issue.
- Thread starter
- #17
Ah s*** am I supposed to have the key forward! … of course …
Ok lemme retry this stuff now - what a dumb mistake. But yes with no key there should still be a couple things getting power and I think when i dis-attach the neg battery cable they don’t get power even if positive cable is hooked up. Is that incorrect?
But is that strange that when I put 5the meter on 200mAmp - touch black to ground cable and red probe to negative post (with positive post connected, my starter reacts? Is that because by touching the two leads to ground post and cable it completes the ground circuit and fires the starter!? - by the way that was all with zero key in ignition at all.
Ok lemme retry this stuff now - what a dumb mistake. But yes with no key there should still be a couple things getting power and I think when i dis-attach the neg battery cable they don’t get power even if positive cable is hooked up. Is that incorrect?
But is that strange that when I put 5the meter on 200mAmp - touch black to ground cable and red probe to negative post (with positive post connected, my starter reacts? Is that because by touching the two leads to ground post and cable it completes the ground circuit and fires the starter!? - by the way that was all with zero key in ignition at all.
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- Thread starter
- #18
Wait no I’m testing for parasitic battery drain when car sits all night - that’s key off … so my epiphany was misplaced lol. Ok I’m gunna try that volt test instead of amps.
You say that your starter reacts - what exactly does that mean?
You have a 200mA fuse in line with your battery, so if it's cranking the engine then there's something very odd!!
Maybe a relay was just chattering somewhere?
Didn't you bypass the ignition switch previously to get it started? Did you leave the carb solenoid connected directly across the battery perhaps?
You have a 200mA fuse in line with your battery, so if it's cranking the engine then there's something very odd!!
Maybe a relay was just chattering somewhere?
Didn't you bypass the ignition switch previously to get it started? Did you leave the carb solenoid connected directly across the battery perhaps?
- Thread starter
- #20
I mean right when i touch the probe to the neg battery post while other probe is securely connected to disconnected battery ground cable, there’s an immediate noise down by the starter. Like I’m completing a circuit by doing that or something. Could be a relay - but it’s not a clicking it’s a churn sound if I can describe it.
No I did not bypass - I was able to hook everything in correct. I was waiting for a new ignition switch in the mail for my other column that I’m gunna use. But I attached my other column which has a different ign switch that works. I just got the other ign switch in the mail so once I install that I’ll let you know how it works out.
