Master switch

I was looking at the battery in my new ride today trying to decide where to put a master switch. Anyone on here done one yet? If so where did you put it? I am concerned that next winter the battery will go dead in the cold when I leave it at the trail head. Not a whole lot of space right next to the battery and I am hesitant to cut & splice main battery cable because of possible warranty issues later on.

 

The Toyota ignition system turns the truck off almost completely. No maker goes as far as Toyota to disable power draws. I’ve left my truck up to 3 weeks when out of town for work and it’s started just fine.

 

Does the evap system require the battery to be hooked up to function?

 

You should be able to mount a battery disconnect switch in the space between the master cylinder and the under hood fuse panel . the only wire you really need to disconnect is the smaller wire on the positive terminal that goes to the fuse panel . The main cable only goes to the starter so if you disconnect the one to the fuse panel everything in the truck is off .

 

Another super easy solution would be to just get a portable battery jumper. I've used mine countless time on mostly other peoples vehicle and it works great. I keep it behind my seat and charge it up every other month or so to keep it topped off. So if your battery does die, you got a quick way to get back on the road.

 

Yes the evap system needs the battery to run its leak check

 

I imagine so. I’ve put my very sensitive DC Clamp-on meter around my battery cable to measure current draw with the truck off, and it’s less than the sensitivity of the meter, which I believe goes down to 10 milliamperes of resolution. If the evap system comes on, that would change. How often does that run?

 

I think it checks at 4 to 6 hours after the truck has been turned off. I am not exactly sure what the intervals are for its system checks.

 

it runs like 4 hours after the truck has been parked. but it also has to see the right amount of fuel in the tank, the right coolant temp. then it will run. new cars and trucks it runs more often then older ones. but it only runs the test once per key cycle . so if parked for a week it only runs 1 time

 

A quick question, what is the evap system? Is that what I possibly heard running for a few minutes when the truck was off last night?

At 40 degrees below zero it does not take long for a small draw to become a dead battery. Batteries are less efficient in the cold to begin with and once they draw down they freeze and crack. I generally leave a vehicle at a trailhead for a month or two in the dead of winter when I am out trapping. If it was not for the fact that I have cracked cables before I would just unhook the battery but I find moving cables around at those temps is not a good thing.

 

Thanks.

 

The Evap system is what the government has made into laws . the protect the planet . and it keeps the fuel fumes from escaping into the atmosphere. the other benefit is when you open the gas cap it does not have a bunch of pressure spitting gas out at you .

 

So it runs (and the computer controlling it) all the time on a 4 to 6 hour cycle? Just for some fumes? Wonder what else is running in the background.

 

About 5 hours after you turn the truck off you can hear it, kinda sounds like the fuel pump is running

 

That would be what I heard last night then. It is what got me thinking about a master switch. All my other vehicles are old enough that they don't have any computers in them.

 

No it only runs 1 time per ignition cycle so if you run your truck and turn off the key after around 4-6 hours it run the test . then if you do not use your truck it just stays off until the next time you start and drive the truck . also running in the background is your clock, radio memory, and the trucks computers all storing memorys .

 

Is anything else running besides the evap system? I know I don't have a security system but I could swear I saw some light flash in the cab when I went outside to smoke last night, but I can't figure out what it was and I never lock my truck anyway.

 

See above for list of running items. I’ve gone out of town on work/play trips and left my truck at home for weeks at a time, never had an issue with starting. I’m a paramedic and we have disconnect switches in the side of the driver seat, on the seat mount. It’s good spot, people remember to use them when they are there. But honestly, I don’t think these trucks need them unless you are leaving it for a super long time

 

If it's only going to be used occasionally, it would be much cheaper and easier to just disconnect the battery cable.