Replace Clutch Start Prevent with Neutral Start Allow
 

1999 with cruise control and MS3-Basic. Manual Transmission

Would like to replace the clutch start prevent safety switch with a relay that is activated by the neutral detection switch on the tranny.

Best I can tell, I could do this by
1) Disconnecting the neutral switch form the ECU
2) Running hot from the Clutch switch to both the coil and one contact of the relay.
3) Running the other relay lead to the the neutral detect switch.
4) Connecting the other clutch switch lead (the one that goes to the solenoid) to the second contact of the relay.

Now clutch and be left out, but XMSN must be in neutral to start.

3 (4) Questions:

Any reason this won't work?
Will the MS3 miss the signal from the neutral switch? If so, what features will be killed?
Will the Cruise still work OK?

It's a lot simpler to just override the clutch switch so you can engage the starter at any time, and then just not turn the key when it's in gear unless you really want to.

--Ian

In the future, just "clutch switch" will do.

For the title?

I want to let others drive the car, and the fewer special instructions, the better.

Neither of these functions will be affected in any way.

Not sure if you're aware (I'm slightly drunk, and didn't entirely follow your description) but to be clear: There are two clutch switches. One small switch is up at the top of the shaft under the dashboard, which detects when the pedal has just started to be depressed. This is the one which feeds the cruise control system and the ECU. Then, there is a second, much larger clutch switch mounted to the firewall, which is engaged only when the clutch pedal is fully depressed. It is this switch which is inline with the path between the ignition switch and the starter solenoid.


So, disconnect the neutral switch from the ECU (the MS isn't using it) and use that to drive the relay. Put +12 from the W/B wire on one side of the relay coil and the "C" contect, and connect the other side of the coil to the violet wire coming off the neutral switch at ECU 1V. I can't remember off-hand whether the neutral switch is open or closed when in neutral, so unless someone else had that data readily at hand, but a SPDT relay and experiment to find the right one to connect to the B/R wire.

You'll need a fairly stout relay, as solenoid current passes directly through that path. Example: NTE R51-5D40-12F 50A 12 VDC SPDT Automotive Relay | 075-138



Also, for reference:

https://www.miataturbo.net/attachmen...1&d=1394888911


https://www.miataturbo.net/attachmen...1&d=1394889378




That said, in my own cars I simply jumper across the lower clutch switch and call it a day. Nobody stupid enough to try and start it with the transmission in gear is allowed to drive. (Note that this philosophy usually bites me in the ass the first time I get into the car after it's been parked by a valet or the guy at the smog-check station, as they always seem to park it in gear...)

Joe, Thanks.

You understood my request perfectly. I can determine action of neutral switch with ohmmeter and get the appropriate relay action.

Yes, lots of current, hence the relay and not the switch (assuming it closes in neutral) directly.

Oh, and thank you for the honest, "That said" paragraph at the end. Indeed, sometimes that 'other guy' turns out to be 'us', creatures of habit that we are.

Case Closed