Parasitic Draw

[aeo]

I have something that is sucking the life out of my battery.

To test for this I disconnected the black terminal from the battery, put my mult-meter between the battery and the cables. It read 12v, it should read zero correct? Then I pulled all the fuses and no change. I turned on all the switches and nothing changed. Obviously I'm missing something, just not sure what to do. Not sure exactly when this started- it was at the shop so it's something since the engine replacement. My thought is that something is just wired in wrong from the swap.

This is on the 300tdi 110.

 

[jymmiejamz]

You need to be measuring amperage, not voltage. You want to see less than .02A or 20mA

Measuring voltage in the way you are is effectively performing a voltage drop test on the battery ground which is showing 12V because it is disconnected. If the cable was connected but corroded and you measured between the post and the cable you might see 3V, for example.

 

[aeo]

User error, oops.

I went to do this again measuring amperage and got .16 for the draw. I have pulled all the fuses in the center fuse panel and under the passenger seat. No change in the draw. Thoughts on where to look next.

 

[Red90]

Alternator. Anything connected by a previous owner.

You should also have a main fuse panel in the engine bay if this is a stock 300TDI truck.

 

[Uncle Douglas]

Does your truck have one of land rovers clocks ?

 

[jymmiejamz]

Always look at aftermarket stuff first, but as @Red90 said, the alternator is also a likely cause. Easy enough to disconnect...

 

[aeo]

Not a stock 300tdi. No LR clock. How is the alternator the cause?

 

[Red90]

Not a stock 300tdi. No LR clock. How is the alternator the cause?

Leaking diode allowing back feed. Disconnect it and see if the power loss goes away. If not, then there is some other unfused item connected and you will need to hunt.

 

[RBBailey]

Other than fuses, and the alternator, is there anything else that you should disconnect to see if the draw goes down?

For instance, does disconnecting a tail light constitute a part of this type of test?

 

[jymmiejamz]

Other than fuses, and the alternator, is there anything else that you should disconnect to see if the draw goes down?

For instance, does disconnecting a tail light constitute a part of this type of test?

The tail lamps are fused, so removing the fuse would eliminate them as a possible cause

 

[RBBailey]

Right, but the process might be something like: Pull a fuse, see that the draw goes away, but the fuse is for the cig lighter, tail lights, interior fan, etc.... so at that point you go to each of those items and.... disconnect the ground? or power? or does it matter?

And when there is a draw detected, is this likely to be a ground issue?

 

[def90]

Always look at aftermarket stuff first, but as @Red90 said, the alternator is also a likely cause. Easy enough to disconnect...

I had a draw from a bad alternator. Easy to diagnose easy to replace.

 

[aeo]

Sadly it wasn't the alternator. It was an aftermarket remote start for my Webasto...new thread on that mess to come, fuse was in the dash.

 

[Napalm00]

if you have jacked up wiring from the PO , id take a weekend and pull out everting that isnt connected. test each circuit and clean the fuse block , will save you so many headaches.