Clutch versus brake safety switch question

[TXJosh]

Hello all
I am building a mkiv with a BPE347 / TKX, with internal TOB.
My wilwood pedal box originally came with a clutch quadrant but i have swapped out for a hydraulic set up.

I am using the two plunger style switches supplied by FFR and have them mounted in the specified bracketed locations per the wilwood instructions.

My question relates to the switch activations. Obviously for a clutch we want the plunger to be largely springed out (extended) prior to the circuit being activated and with the brake we want it just barely extended so that the lights go on as soon as braking pressure begins.

I get that these switches have grooves and can be screwed deeper or less deeper in the bracket, but still am having trouble making sense of the clutch.

Any advice is greatly appreciated.

Thank you

[edwardb]

The clutch and brake switch are actually mounted and actuated similarly with the button pushed in when the pedals are in their resting position. When the brake pedal is pushed the button extends closing the switch which completes the brake light circuit and lights the brake lights. When the clutch pedal is pushed, again the button extends closing the switch which completes the Ron Francis start circuit (the blue wire) and actuates the solenoid on the starter. Don't overcomplicate with other factors you've listed, e.g. internal TOB, hydraulic vs. cable clutch, BPE347, TKX, etc. None of those change the standard setup. The slight downside to this setup (my opinion) is you don't have to push the clutch all the way down to close the circuit and allow the engine to start. In practice, I doubt you would do that. Normally you would just push it all the way down every time. But just saying... One thing to watch, and I don't know if the manual has been corrected, but some have reported the wrong connection terminals are shown in the manual. The switch has two pairs of terminals. Normally open (NO) and normally closed (NC). You want the pair that opens when the button is in and closed when the button is out.

Not to confuse the answer, but a Coyote installation has it's own clutch safety switch and wiring. So you don't use the kit provided switch or blue start wire.

[TXJosh]

Fantastically clear , and thank you.
I suppose my confusion stemmed from the fact that with this set up, the car can be started with the clutch pedal only minimally depressed. I agree, practically speaking, this is not a big deal as any conscious effort would eliminate this middle state ignition. But, that's the inconsistency my brain was attaching to. So just set both switches up the same way and let the electronics take care of the rest?

Appreciate it.

[rickster991]

The TKX has a neutral switch available. I opted to use that instead of the clutch. This allows you to start the car without sitting in it if you need to.

[Mike.Bray]

The TKX has a neutral switch available. I opted to use that instead of the clutch. This allows you to start the car without sitting in it if you need to.

I started out using the clutch as a safety switch but changed to the neutral switch in the TKX like Rickster. Like that setup a lot better.

[eljessup65]

I started out using the clutch as a safety switch but changed to the neutral switch in the TKX like Rickster. Like that setup a lot better.

Has anyone used both and run them in parallel? Any downside to using both?

[rich grsc]

EVERY car manufacturer uses a manual clutch safety switch. Why is that? :rolleyes:

[edwardb]

Has anyone used both and run them in parallel? Any downside to using both?

That's what I'm doing with my Mk5 build. No downside that I'm aware of.

[Presdough]

'm using the neutral switch also. The only downside was breaking the clutch cable and not being able to start the car in gear...

[Dgc333]

Has anyone used both and run them in parallel? Any downside to using both?

The down side is you have added another point of failure with zero added functionality. From a statistical standpoint assuming both switches have the same reliability you have doubled the probability that one other the other fails and you can't start the car.

[OB6]

The down side is you have added another point of failure with zero added functionality. From a statistical standpoint assuming both switches have the same reliability you have doubled the probability that one other the other fails and you can't start the car.

This is why I chose to use a CSS instead of the TKX neutral safety switch, which is known to fail with very little amp draw. You could insert a relay into the circuit, but then there's another potential point of failure. I also installed an override switch primarily so I could start from outside the car, but I guess it also serves as redundancy in case the CSS fails (unlikely).

[edwardb]

Point of clarification about my post #8 where I stated I'm using both a clutch and neutral switch from the TKX in my Mk5 build. Wired in parallel so either would allow the engine to start. The build is an Aluminator (aka Coyote) with a Coyote control pack. Two things: (1) The clutch switch is the Ford Performance switch which only actuates when the clutch is pushed all the way in. Unlike the standard setup. (2) The control pack only uses the switch(s) as a signal to the computer to initiate the start. Even though it's relatively low, the actual current to the starter solenoid is through another dedicated wire in the control pack harness. So neither switch is seeing any appreciable current.

Theoretically both switches have some kind of MTBF rating and together the rating might be technically lower. But wired this way, neither switch failure would prevent a start. They would both have to fail. Unlikely IMO. I like the idea of having the usual clutch down safety aspect and in practice would be the most common. But I also like the idea of occasionally, e.g. when working on the car or whatever, not having to sit in the seat and press the pedal. Just make sure it's in neutral.

Ok, a lot of words. But why I answered I don't see any downside. At least for the build I'm working on. :rolleyes:

[Dgc333]

Having them wired in parallel increases the reliability of the safety function. I assumed you had them in series.

[JMD]

The TKX has a neutral switch available. I opted to use that instead of the clutch. This allows you to start the car without sitting in it if you need to.

I did the opposite. Used only the clutch safety, wired the neutral safety wires together. Having both is redundant and superfluous, in my opinion. Pick the one you prefer.

[JMD]

Having them wired in parallel increases the reliability of the safety function. I assumed you had them in series.

I believe parallel allows either one to provide the 12v power to the starter relay that it needs to crank. Doesn't require both. Great idea.

[Waterman]

I feel compelled to comment for 2 reasons. Neutral switch is a must for me. I use it ALL the time as we are constantly tweaking the Cobra and you know it is a bit of a pain to get in and out quickly. I used a relay and not too concerned with failure as we all know the screwdriver trick at the starter, plus I always check it is in neutral as habit. As far as the brake switch I did NOT like how touchy it was to set actuation early in the travel. I moved the sw mounting location lower so that I can just touch the pedal and lights(including a 3rd) come on to warn tailgaters. See https://thefactoryfiveforum.com/showthread.php?49630-Watermans-MKIV-Build-Kit-207937 Post #20

[PMD24]

EVERY car manufacturer uses a manual clutch safety switch. Why is that? :rolleyes:

Cheaper?:)

[PMD24]

I don't want to hyjack TXJosh's thread since it has shifted from his question about the brake and clutch switch actuations, so I will post a separate thread with the question of clutch vs neutral vs both. I've been kicking it around in my head because I'm at that point in my wiring and would like to hear everyone's thoughts on the topic.

[rich grsc]

Cheaper?:)

No, safety & liability concerns

[Jeff Kleiner]

Clutch switch for sure.

So, my sister was taught (like me) to park the car in gear always depress the clutch to start it. My brother in law was taught to always park in neutral and not to depress the clutch to start. Many years ago shortly after they were married and before the manufacturers started making cars idiot proof they were visiting me and my sister parked their car. When they got ready to leave my b.i.l. got in, started their old Mazda without depressing the clutch and ran through my garage door. True story.

Jeff

[OB6]

You'll need a clutch switch anyway if you want to install cruise control.

[PMD24]

Clutch switch for sure.

So, my sister was taught (like me) to park the car in gear always depress the clutch to start it. My brother in law was taught to always park in neutral and not to depress the clutch to start. Many years ago shortly after they were married and before the manufacturers started making cars idiot proof they were visiting me and my sister parked their car. When they got ready to leave my b.i.l. got in, started their old Mazda without depressing the clutch and ran through my garage door. True story.

Jeff

I learned that way as well. That's why my emergency brake was always froze up when I needed it (never used it):)

But, what you describe is what got me thinking initially. If that old Mazda had a neutral interlock the door would be saved.

So far, between this thread and the other one I started, clutch switch seems to be winning the race, but I keep thinking neutral interlock is safer. Is there something I'm not considering?