Electrical question

[overandunder]

so my car(89 camry all trac) has a really bad parasitic draw and im too lazy to try to find it lol, so i want to use this as a little exercise with what i've learned so far. I drew up this schematic, just need it proof read before I electrocute myself lol.

Its a battery cut off switch, having a manual one is no fun. the 1st pic is painless performances starter cut off solenoids so i know its rated for this amperage/application. In the 2nd pic is the relay i'd be using. the relay is rated for 500 amps and a 700 surge and is typically used in sounds systems/isolator for a dual battery set up. if i set each ground straight back to the battery it wouldnt draw as much has chassis ground when the system is off (especially the relay ground, switch doesnt matter).

let me know what you think.

 

[mk378]

The way you have it drawn will not work because there is no path out of the battery when the relay is open. So turning the switch on will not energize the relay. The switch needs to return to battery minus, not chassis ground.

Also consider that disconnecting the battery while the car is running is prone to cause a severe voltage surge which can damage things.

If you want to learn about electricity I'd suggest finding the problem with the car would be a good exercise.

 

[atikovi]

In the time it took to come up with that idea and draw it all up, you could have found the lol draw by now.

 

[Silver]

I'm betting you don't care, but each time you cut power the memory of the pcm, etc will be lost. You'll theoretically get worse mileage, etc.

 

[overandunder]

The way you have it drawn will not work because there is no path out of the battery when the relay is open. So turning the switch on will not energize the relay. The switch needs to return to battery minus, not chassis ground.

Also consider that disconnecting the battery while the car is running is prone to cause a severe voltage surge which can damage things.

If you want to learn about electricity I'd suggest finding the problem with the car would be a good exercise.

I should have put a symbol that my bad. when the relay is open, i would allow the negative to flow through the car, powering the car.

I should have also added that i only drive this thing maybe once a month. i live in MN so its only really used when it snows really bad and the plows arent very effective. i searched everything i could without taking out the dash and I cant find the draw. when it get swapped is when ill actually find it and fix it.

Ive gotten heated/cooled seats to work in a buddies EG hatch, and a bunch more small things. I want to make sure this will work, because of the amperage. get it wrong, and it'll fry car, or worse.

 

[atikovi]

Maybe just disconnect the battery cable when you don't plan to drive it?

 

[overandunder]

Maybe just disconnect the battery cable when you don't plan to drive it?

did you even read the post? or just skim it over.

 

[overandunder]

Maybe just disconnect the battery cable when you don't plan to drive it?

Not to come off as an ahole, but ive answered both of your questions in op.

 

[fsdork]

Which fuse did you trace the draw to before you determined the problem was buried in the dash?

 

[KJSmith]

Not to come off as an ahole, but ive answered both of your questions in op.

Too late.
A guy took the time to respond.
If you don't like the response just pass it by, no need to dog him.

 

[ollie]

so my car(89 camry all trac) has a really bad parasitic draw and im too lazy to try to find it

If that's the case then you need to purchase an Amp Hound. This slick tool has saved me hours finding odd electrical draws. After you find it most times it ends up being a bad ground to the chassis.

 

[overandunder]

Which fuse did you trace the draw to before you determined the problem was buried in the dash?

Automatic seat belt retractor, cig lighter, and the radio, and a third that has it label warn out. i pulled out as much has I could and they were all drawing. Actual parts were powered on. there is either a chaff in one harnesses, grounding them, or something with the seat belt (stuck on open) causing the ECU to think there is still a passenger.

 

[eljefino]

The coil draw for a 500 amp relay is itself going to be substantial. I have a 100 amp relay in my RV for charging the second battery and it's 500 mA.

You might want to sequester your circuits slightly more, so some aren't involved in this relay. Does the alternator have its own 100 amp fuse? That's a contender for your draw-- shorted diode. The starter, obviously, shouldn't need to be involved in this-- it's already isolated via its own relay.

Edit, I would really, really look at that automatic seat belt system. Maybe convert the passenger side to manual by unplugging its motor.

 

[overandunder]

If that's the case then you need to purchase an Amp Hound. This slick tool has saved me hours finding odd electrical draws. After you find it most times it ends up being a bad ground to the chassis.

I was really debating it, but it would be the only time i used it. I know this is a dumb project, but one that would be fun to get done if it works.

 

[overandunder]

The coil draw for a 500 amp relay is itself going to be substantial. I have a 100 amp relay in my RV for charging the second battery and it's 500 mA.

You might want to sequester your circuits slightly more, so some aren't involved in this relay. Does the alternator have its own 100 amp fuse? That's a contender for your draw-- shorted diode. The starter, obviously, shouldn't need to be involved in this-- it's already isolated via its own relay.

All the fuses are fine expect for the ones listed, im confidant its under the dash. If you were to make some changes to the schematic, what changes would you make? its crude for sure, and the coil draw is one thing I was nervous about.

 

[eljefino]

There are some mega fuses under the hood that feed the ignition switch and or internal accessories. I'd yank them individually and put an ammeter across them to find the one with the high rest current. Then relay that one.

You'll probably have some LOLs as the power seat belts boot up when you flip the switch on. The natural end of all this would be rigging it to your ignition switch.

 

[benjy]

a simple + cheep battery disconnect can be used. turn the knob all is OFF!!! of course newer cars can be a PITA with resets. my rarely driven TT roadster looses radio pesets, NO biggie turn the knob ON + you have a pretty fully charged battery!!! samo on my classic 56 belair!!

 

[overandunder]

There are some mega fuses under the hood that feed the ignition switch and or internal accessories. I'd yank them individually and put an ammeter across them to find the one with the high rest current. Then relay that one.

You'll probably have some LOLs as the power seat belts boot up when you flip the switch on. The natural end of all this would be rigging it to your ignition switch.

Sounds good ill give it a check when i get some time here soon. since they're only a 100 amp I dont have to run that big nasty solenoid/relay so thatll help a lot. my prediction is that the interior fuse is gonna pull the most, would make the most since to relay that one given the situation. might even add a 2nd switch for the other fuse.

 

[JHZR2]

I should have put a symbol that my bad. when the relay is open, i would allow the negative to flow through the car, powering the car.

I should have also added that i only drive this thing maybe once a month. i live in MN so its only really used when it snows really bad and the plows arent very effective. i searched everything i could without taking out the dash and I cant find the draw. when it get swapped is when ill actually find it and fix it.

Ive gotten heated/cooled seats to work in a buddies EG hatch, and a bunch more small things. I want to make sure this will work, because of the amperage. get it wrong, and it'll fry car, or worse.

Then redo the drawings if you want a sanity check.

I’m not seeing a path to complete the circuit around the relay coil / manual switch, and can’t really conceptualize what you left out. Re-creating a path on the negative side would let the parasitics still work.

My suspicion is that you need to switch the car positive, possibly by switching the relay ground. This way you completely isolate all the power to the car’s loads, but you can keep the grounds in tact including to switch the relay coil.

I had to deal with parasitic on my 93 MB 300SD. Millivolt method across fuses only work but so well. It took strategically pulling fuses, but I isolated it to one sticking relay.