Truck struggles to start

This seems more dangerous to me. My thinking is you need to remove the positive first as it removes the energy. If you take off the negative first and that touches metal, doesn't that complete the circuit again? Where as once you remove the positive, the circuit stays unbroken unless the wire touches the positive terminal again.

Please help me understand why my thinking is not correct

 

Are you referring to changing a battery (or disconnecting the negative terminal while you work on something) or are you referring to the jumper cable scenario?

I'll try to clarify, but it'd save time if I better understood your question.

 

both actually, I have always removed the positive first, at least I think I have.

 

If you pull the positive terminal and your wrench touches the metal body you just created an Arc Welder.

 

@shakerhood gives the short answer.

For the longer answer: let's start with the changing out a battery or working on the electrical system.

Once you remove the cable from either battery terminal you've prevented a short circuit. It really doesn't matter which from a purely electrical standpoint. The battery creates a "potential" between the two terminals, it's not like the "energy" is in one of them preferentially over the other.

The reason for disconnecting the negative terminal is purely that there's always some chance of slipping and hitting the other end of your wrench against the body or something. If you're working on the negative terminal, it's no big deal since they're already connected together by the negative battery cable. If you're wrenching the positive terminal with the negative terminal attached and hit the body or block with your wrench, things can get real exciting real quick.

Now for the jumper cables. The big risk here is that the dead battery might be venting a little bit of hydrogen (less risk of that with a charged battery). You'd really rather not have a spark right up close to the battery. So you first connect the positive lead to the dead battery, making sure the other end positive isn't shorted out or touching anything. Then connect the other positive to the good battery and it's safely out of the way. Third, connect to the good battery negative terminal. No spark since there's not a complete circuit. Finally connect the last connector to the block or body of the dead battery car away from the battery since you will likely get a spark.

Does that help?

 

Thanks. On the wrenching the positive cable, no matter where the negative cable is, if your wrench hits the truck while also touching the positive terminal, won't that create the arc?

 

Not if the negative cable is disconnected from the battery.

You'd only get spark if you make an electrical connection between the two terminals of the battery. The negative cable is what connects the body to the battery. Disconnect it and you're now much safer to work on the positive terminal since at that point contacting the body can no longer make the connection to the negative terminal.

 

its coming back to me now. Thanks?

 

OP, can you tell us what model battery you have now, and what model wasn't working that got replaced? Just curious what the inadequate one was...

 

If the Dealer replaced it then my guess is the new one is a Tru-Start

 

Yes, that'd be the brand, but which model? 24F, 27F, or something else?

Either way, stuff happens. New batteries sometimes fail prematurely. The Tacomas are specc'd for 24F or 27F batteries.

The real question is whether the truck had the correct battery and it was just defective, or for some reason had an incorrect battery.

 

Maybe the OP added some accessories that are draining the battery.

 

If so we'll find out in the morning. Doesn't seem to match the first sentence of the original post though. He described a classic weak battery scenario to a T

 

Sounds like you need to find a new tech.

 

Has it been starting ok since they replaced the Battery?