Battery Disconnect Switch Question

[hala514]

Hello,

I was planning on putting in a battery disconnect switch with my roadster for its safety benefit. Specifically, this one:

http://www.summitracing.com/parts/FLA-FR1002/

Then I started thinking it would be a nice additional security feature as well if I got a keyed one, BUT, if I used it that way I would be turning off keep-alive as well.
Has anyone out there cut into the harness to do this? Circuit diagram shows it might be easy - bring a separate 12V into pin62 on the 70 way PCM connector.

Thoughts? Wanted to get some feedback before I do something potentially stupid.

Second more minor questions is: what are the purple and pink wires that are "hank-taped" to the gas pedal loom? (proper usage of hank-taped?)

Thanks,
Ted

[Jester]

I used the same set-up as per FFR install instructions and used a master cut-off switch in line between the battery and starter. I do not use any keep alive functions - no need to cut into the harness. The added safety with the battery disconnect outweighs any keep alive functionality (IMHO).

[hala514]

yikes i wouldn't do that if you use the cutoff for more than just the safety aspect... your adaptive fuel trims, learned cam offset, etc potentially all get erased on every loss of power. They are not supposed to as they are written into NVRAM, but they can get corrupted and reset - depends on what the state of the PCM is when the cutoff gets pulled. (How do I know this? I am an engine calibrator at the big F.)

The end result of this is basically that you might have a rough feeling cold start after each KAM clear. There are cal features in place which will prevent the engine to stall, but you will feel it stumble a little.


I am planning on hiding the disconnect behind the dash, accessible from underneath. It will kind of be in the middle of the dash area near the FP, this worked out pretty well as a spot where the RF 12v leads terminate because of their short length. Also this is where I am sticking the PDB. I ran 12V like this: Battery --> Starter Post --> Master Cutoff --> everything else. So the hot feed to the starter doesn't get cut off, but if I pull the disconnect, the PCM and the ignition feed to the starter would get cut. Should be OK?

[Jester]

Interesting - I was advised that this set up will not interfeer with ECU memory?

So far no issues with using the cut-off switch as I have discribed.

If you have details on your set-up, please pass along.

Thx

[skullandbones]

There is a low voltage circuit that will allow you to cross over the two cutoff switch posts to keep power to all circuits but mainly to the PCM. There is a resistor or whatever device that prevents the full 14 volts from crossing so it would still prevent a startup. Therefore, no messing with the harness wiring. If I can find that website, I will send it to you. Sorry. WEK.

[Jeff Kleiner]

I simply use a 10 amp self resetting circuit breaker across the two poles of the cutoff. It powers the KAM but will not allow a start or large current draw such as might occur with an alternator malfunction. If you inadvertantly forget to turn the master power on (only done it twice in 14,000 miles) the breaker pops but comes back in a couple of seconds---beats using a fuse that would have to be changed.

Jeff

[JeepFlyer]

hala,

I was thinking the same thing as you. The keep-alive sounds like it serves some purpose, and it wouldn't be built into the system if it didn't serve some kind of purpose. You can always solder two wires back together. Like you, I'm not there yet either, so I'm sure it's easier said than done.

Here is what I was planning... a battery disconnect switch in an easily accessible (and visible) location, purely for safety reasons. Then a switch tucked up under the dash wired in series with the starter switch to the solenoid. Safety for the occasional track day, and security from the random parking lot opportunist. I'm also leaning towards hotwiring my electric-hydro power steering switch to either an accessory switch or it's own, for times when i need to move the car without starting it up. Haven't decided if that will be completely necessary or just "nice" and not worth the extra work.

I have no idea if the Coyote could be push started, and/or what kind of damage it could do, but I doubt someone looking to make a quick getaway would try that hard.