so I have a short circuit in my 94 pickup and do not have an idea where it might be .. it occurs during the rainy season and somewhere a wire short circuits resulting in a full-time draw of around 3A if I remember correctly. I have tried pulling all the fuses and the drain still remains.

I have a manual screw positive terminal disconnect now, but would rather not have to pop the hood every time after parking, not to mention the possibility of forgetting. Got the idea of putting a solenoid/relay between the negative terminal and chassis ground. Then hard wire the battery to the solenoid coil lead with a momentary switch in the cab between. Additionally the 12V ACC lead from the ignition/stereo harness connected to the coil lead would kick on and stay on until the car is turned off at which point the solenoid would open.

Anyway, this is all more tangible and clear in a wiring diagram -->

 

Have you done a parasitic draw test?

 

Indeed, an ammeter between the positive battery post and the bracket during the wet season reads a steady 3A. I have already killed one battery over a winter while unaware of the drain.

 

And you havent tracked it down by pulling fuses?
the draw has to be somewhere.
any aftermarket wires?

 

I cant quite follow your work around. Whats the new path to the main fuse box?
how is the relay going to cut the draw?
Im just trying to understand. These phantom draws are the worst.

 

I have tried pulling out the stereo but don't have much hope finding the draw that could be anywhere on an older truck ..

essentially breaking the circuit at the negative lead

 

The flaw in your plan, you've got a multi ground system. The head connects to the body, the ECU connects to the head thru the intake, the alternator connects to the block which is connected to.the body, and there is an in the cab ground on both sides of the cabin....


So with all your ATC fuses out you've still got a draw those means your parasite is directly connected to the distribution block via one of the primary fusible links...

3 amps, possibility a bad alternator rectifier. (That 3amps seems to ring a bell!)

 

If pulling fuses doesn't change anything, the short is between the battery and the fuse box. Physically a short distance, through there are plenty of opportunities for disappointment on the underside of the under-hood fuse box.

 

not sure what you mean by a multi-ground system .. my understanding is that the block/body/cab is all connected to the negative terminal of the battery.

 

I would bet your alternator has an internal short. Unhook the alternator and see if your draw goes away.

 

cool I'll remember to get the lead off the alternator the next rainy season .. would the water somehow trigger a short in the alternator though?

I'm still wondering what people think about the feasibility of this automatic open circuit to disconnect the battery ..
could be a good anti-theft mechanism, even without a parasitic drain?

 

Look at your battery negative post, it should have a medium sized wire that goes to the fender, it also has a larger sized wire that goes the the motor mount.

Now look at the (sticky?) Thread about ground points.. All of these grounds are semi redundant (IE interconnected). I'll go over them again. You have the big battery negative connected to the engine block near the right hand motor mount, this is electrically connected to all the other ground points, one on the lower intake (path to ground ->lower intake -> engine block -> big battery cable). Now suppose you put a big ass Ford style starter solenoid on the big ground wire.. You have an alternative path lower intake to head to rear of head ground to fender ground. If you trigger the starter the braided ground strap will probably handle the current but the battery to fender wire is going to most likely melt..

You following now about the multipath ground? I only illustrated three wires here and there are two more on the engine and two more on the body not counting the ignition system which if you fry is not replaceable out side of a salvage yard..


TL;Dr test your alternator diodes!

*summons one of the electrical engineering GUYS*@RAD4Runner

~50 WATTS is a lot of parasitic draw, that's going to drain the ~20 amp hour reserve of the battery in under 12 hours.

What non factory wiring do you have, you mentioned an aftermarket stereo I recall.

 

Flawed

 

Second that. For same amount of time and materials, I'm sure you can properly fix the problem.

So you did not remove the fuses one at a time as suggested?
OR remove each fuse, insert your current measuring set up where you removed that fuse.

If it's a bad alternator rectifier as mentioned above, your workaround will not work.
It takes less time and energy to disconnect thick "B" wire from alternator and measure resistance from terminal to ground stud than "wondering".

Yes, and that could give you your 3A drain like a bad rectifier could.

 

You following now about the multipath ground? I only illustrated three wires here and there are two more on the engine and two more on the body not counting the ignition system which if you fry is not replaceable out side of a salvage yard..
[/QUOTE]

So by multi-ground you essentially are referring to multiple attachment points to the same ground ..

Problem is the drain does not exist currently as it has been dry so I don't believe it can be readily isolated.

What is flawed about putting a solenoid between the negative post and the two wires that connect to it making sure the amperage rating is equal or greater than the largest wire (to the engine block)?

 

you idiots say the proposed circuit is flawed because it would be preferable finding the short --
the original post was about the feasibility of the relay circuit not about finding the drain.

 

Don't forget to do your math for starter draw and stall current..

 

Play nice, keep it up or you get a vacation. you came here looking for advice, you have received advice that is sound advice from an electrical stand point.
Bypassing your electrical issue is a bad idea, take these guys advice

 

1.4kW starter / 12V = 117 Cranking Amps...

 

I've forgotten the duty cycle for the starter from the owners manual. I'm fairly certain about 30 seconds out of "some" minutes where "some" is either 2/5/10.

125 amp continuous current solenoids seem reasonable priced and let's you use the clutch start cancel (starter crawl) untill the primaries and starter cry for mercy and start to fail.