34 replies to this topic

[ChrisA]

Why not just use the Alt Excite wire method Drago recommends? And, if you are really set on using two switches, use the Wheeler method for the switch closest to the Alt. and the Drago method for the switch closest to the Batt & Alt Excite wire.  I think that would work...?

[john mueller]

Why not just use the Alt Excite wire method Drago recommends? And, if you are really set on using two switches, use the Wheeler method for the switch closest to the Alt. and the Drago method for the switch closest to the Batt & Alt Excite wire.  I think that would work...?

 

Mmmmmm, I like the logic but hate the italicized 'think' word...  Corroboration anyone?

[davew]

Mmmmmm, I like the logic but hate the italicized 'think' word...  Corroboration anyone?

I also hate thinking, either in italics or bold

[Tom Hampton]

Schematic for two switches, wired using Wheeler method.  Both switches must be in the ON position, either switch will kill the car.  Alternator B-terminal is always connected positive terminal on battery. 

 

The only thing I don't like about two switches is the extra connections and switch...more wires, connectors, and switches to fail, and kill the car.  

 

Personally, I added a cable pull from my dash to the single switch mounted on the passenger side of the main hoop (wired using the wheeler method).

 

 

 

 

Attached Files

•  killswitch.png   10.72KB   41 downloads

[john mueller]

Thanks Tom !

[Juan Pineda]

I've been puzzling over the technique of intercepting the grey/red wire (in the packet shelf) to shut the alternator down, and I'm not sure I understand how it could work. From the schematic (attached) it appears that the grey wire is the direct signal that enables current to the exciter. The grey/red signal appears to be only a sense voltage that would be used for the alternator warning light.

 

So my question is why would interrupting the grey/red signal disable the alternator?

 

Following the logic, if the regulator (in the PCM) sees no voltage on the grey/red wire then it should enable current to the exciter to start charging. Presumably this is what is needed when you first start the car. So I would expect disconnecting the grey/red should have the opposite of the desired effect.

 

[Jim Drago]

When you break that wire, the ALT stops charging. So if you break the battery cable and the ALT doesnt put out any volts, car dies.

 

I also sent you a PM Juan

 

Jim

[Juan Pineda]

Jim, what's not adding up is why interrupting the grey/red would stop charging? (It would certainly illuminate the charging failure lamp.) The wire that enables the exciter coil is the grey one according to the schematic, not the grey/red. Is there some non-obvious trick here about why this works?

[Tom Hampton]

Juan-

By my read, the gy/r wire is the sense wire for the pcm. When the pcm senses the generator voltage has failed it disables the exciter (gy wire) and lights the light in the dash.

So, breaking the gy/r wire tells the pcm the generator has failed and the pcm does the rest of the work.

[Juan Pineda]

So this is the best explanation I have heard so far: the GY/R wire is actually used to sense the revolution of the alternator. That's why its connected to only one of the three stator windings. So if the PCM does not see any pulses, that means the alternator is not turning, and so no need to supply current to the exciter. Hence interrupting the GY/R wire disables the alternator. I like this explanation.

[Adax]

Very revelvant thread today.

 

I'm wiring up the cut-off switch in my '03 today and there is not grey/red in the harness at the package shelf. It looks like the harness changed. the Gr/R wire now runs from the alternator, does a little loop toward the rear along the + battery cable, then goes to the PCM. The loop is taped from the factory as shown below, you will need to strip off the tape/covering. I've spliced it to my 4-pole switch as Drago describes. not sure how to check it yet but just wanted to let everyone know where it now lives in the '01 vintage.

 

[miata4me]

I am installing a 4 post kill switch in my son's car tomorrow.  Can someone please clarify where on our 99 Miata we will find the gray wire with red tracer?  I'd look for it, but the car is temporarily in another shop.  I know there is a wire harness in with a plastic wrap under the gas tank cover.  Is that where I will find it?

 

I've summarized the 4 post emergency cutoff for a 99 Miata below.  Am I on track?

• Take the positive cable off the battery
• Cut the lead clamp off the positive cable and replace it with a "lug" large enough to fit on one of the large posts on the cutoff switch
• Run that positive lug to the cutoff switch
• Attach a ~40" long battery cable to the remaining large terminal on the cutoff switch
• Find the gray wire with a red tracer line in the wiring harness in front of the gas tank
• Cut the gray with red trace wire and splice in a 10 gauge wire long enough to go to one of the small terminals on the cut off switch
• Run another wire from the other end of the gray red wire to the remaining small terminal
• Attach new positive cable on the battery
• Start the car
• Turning the emergency cutoff switch should now cause the car to stall

[Caveman-kwebb99]

It is under the rear deck hood on passenger side normally right behind where your kill switch is, when you life the pannel there will be a white plug this is where you will find said wire.

[ChrisA]

 

I am installing a 4 post kill switch in my son's car tomorrow.  Can someone please clarify where on our 99 Miata we will find the gray wire with red tracer?  I'd look for it, but the car is temporarily in another shop.  I know there is a wire harness in with a plastic wrap under the gas tank cover.  Is that where I will find it?

 

I've summarized the 4 post emergency cutoff for a 99 Miata below.  Am I on track?

• Take the positive cable off the battery
• Cut the lead clamp off the positive cable and replace it with a "lug" large enough to fit on one of the large posts on the cutoff switch
• Run that positive lug to the cutoff switch
• Attach a ~40" long battery cable to the remaining large terminal on the cutoff switch
• Find the gray wire with a red tracer line in the wiring harness in front of the gas tank
• Cut the gray with red trace wire and splice in a 10 gauge wire long enough to go to one of the small terminals on the cut off switch
• Run another wire from the other end of the gray red wire to the remaining small terminal
• Attach new positive cable on the battery
• Start the car
• Turning the emergency cutoff switch should now cause the car to stall

 

A 10 awg wire is too large for the Gr/Rd wire. It is only a signal wire, approx. 20-18 awg. Incase you want to tap into the line elsewhere. The line runs form the package shelf to the front of the car within the Pos. Battery wire bundle that is clipped to the PPF.

[bones240z]

I have a 2001 VVT car and am working on wiring the 4-post battery kill switch. I have wired the main cable like Dave Wheeler and Jim Drago have suggested. As ADAX wrote above, the alternator excite wire is not in the harness at the package shelf. I am unable to see the picture he posted and was hoping to get some advice/confirmation of my plan to wire the switch. I have 2 - 18 ga. wires from the switch running to the alternator connections in the engine bay. Would this be the correct location to tie in to? Any suggestions for a different way to wire this? Any images you have would be great!

Thanks in advance.