Factory Five Racing Forum banner
1 - 20 of 32 Posts

·
FFR Master Builder
Joined
·
4,170 Posts
Discussion Starter · #1 ·
the main reason for me putting a battery cutoff switch in was a photo i saw on the forum about 1 year ago. this photo was of a FFR cobra that caught on fire in the garage and destroyed the car and the house. i am rewiring the car myself and even though i am doing a good job, a electrical fire is always a concern. after reading and learning how EFI works i realized the computer must have power all the time to maintain memory. i have seen the jumpers on the cutoff switch with the fuses in them. this is so the computer can get power, but the rest of the car can get power to and if there were a short there could be a problem. i suppose i could put a very small fuse in the jumper but what size is needed to maintain powere to the computer
 

·
Justa Member
Joined
·
1,225 Posts
I have a 5amp self resetting circuit breaker as my jumper. Allows power for comp and accesories but if tried to start without cutoff key breaker blows. It self resets once it cools down. Since I don't have to get to Breaker to replace it like I would have to with a fuse, it can be tucked away and hidden.
OJ
 

·
Charter Member
Joined
·
625 Posts
While I'm not close to this part of the installation I purchased the bypass kit(s), to keep the computer hot, from Mark Reynolds at Breeze. I say "kit(s)" because an additional cut-off in a hidden location is going to be part of my theft deterrent system.

You might check it out to see if this won't take care of your issue.

Hank J.
 

·
Orbiting FFCobra.com
Joined
·
778 Posts
I was thinking about putting a hidden cutoff switch on the fuel pump relay for my EFI 5.0. No gas, no go
 

·
Registered
Joined
·
1,207 Posts
You can find the fuses the re-set automatically at PepBoys. I've had trouble finding them anywhere else, but PepBoys always has them.
 

·
Justa Member
Joined
·
1,225 Posts
I bought my circuit breaker at Nappa, but check out what PAB says you might be able to pull it out of your donor.
oj
 

·
Charter Member
Joined
·
972 Posts
I put a 5 amp fuse straight off the battery and ran it directly to the +12V supply on the computer. If I try to start the engine without the cutoff switch made, the fuse doesn't blow, the car just refuses to start. This is the best solution in my opinion.

Dennis B.
 

·
Charter Member
Joined
·
3,487 Posts
Dennis,
I hope you fused it before the computer, I'd hate to see you fry that puter.

That does sound like a good way to go.
Rob Baker
 

·
Charter Member
Joined
·
972 Posts
Yep, that's exactly how I did it. 2,000 miles and no problems.
 

·
Junior Charter Member
Joined
·
121 Posts
I want to put in cut-off switch, just not sure what wire powers the puter. Had the wire diet done for me, so I am not sure what wire supplys the power. Is it one of the wires going into the very large conector on the computer itself, or is it one in the small plug that also goes to puter? Any help would be appreciated sm55
 

·
Charter Member
Joined
·
505 Posts
What about putting the cut off switch on the ground and running a ground directly to the battery from the computer? I thought that a cut off on the ground was a safer bet anyway?

Earl
 

·
Premium Member
Joined
·
18,462 Posts
Every time this topic comes up...I feel that another option should be presented.

Anyway, people who bury the battery under the trunk floor need a battery cut off switch so it can be quickly disconnected for safety.

There are a dozen other ways to disable the car for security besides that battery switch.

I chose to make tha battery accessible and NO cut off switch...just like Ford would have done had they re-created this car.

If I had a hidden battery, the cut-off switch would be accessible if the car rolled. I would not bypass it for the computer and the clock. It would be for emergencies only.

But, hey, that's just me. And I guarantee no strange circuits will get into my electrical system either. Clone Ford's design that are successful on over 1,000,000 Mustangs, and sleep at night. But, hey, that's just me.

Back to how to wire around the cut off switch...sorry. (The
made me say this)
 

·
FFR Driver
Joined
·
2,154 Posts
My take:

I installed a battery cutoff switch so I could screw around all day building the car and sleep well directly over the garage by simply turning it off when I was done. The car was completed 3 years ago and I do remove the key a few dozen times a year for various reasons when I am out driving.

I installed a 3 Amp pushbutton circuit breaker for the dozen or so times I forget to re-install the key prior to starting the car. I am glad its not a fuse mounted in the trunk. It is mounted under the dash in the EM flasher bracket. Z-Racing sells a simple kit.

I will replace the 3 Amp breaker with a 10 Amp breaker as there are times the fan is running when I park. If I remove the cutoff key the fan trips the smaller 3 amp breaker in about 5 seconds.

Wait until you get to the "Which line do I break, the positive or negative?" threads. Much more fun than this!

Good luck.
 

·
Justa Member
Joined
·
1,225 Posts
Scanman55, got breaker at Nappa
OJ
 

·
Senior Charter Member
Joined
·
1,406 Posts
Scanman, you don't need to worry about finding the wire for the computer. Just jump the terminals of the cut-off switch with the small fuse/breaker. That way, when the car is shut down and the switch is open, your fuse/breaker will only allow enough power through to operate the computer. If a short occurs anywhere in the car, the fuse/breaker blows and all power is cut off.

Earl, if the switch is wired into the ground cable to the battery, it will not be able to interrupt the ground to the alternator. So if the car is already running, the battery cut-off won't do anything wired this way. You need to connect one terminal of the cut-off switch to both the battery and the alternator. The other terminal feeds the rest of the electrical system.
 

·
FFCobra Master Craftsman
Joined
·
2,042 Posts
Cobra 3657
I disagree. The alternator is getting ground from the battery. If the ground side of the battery is disconnected the alternator has no ground. On the flip side a alternator after it is energized will continue to make power.
Jeff Hamilton
 
1 - 20 of 32 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top