99 MX-5 passenger central locking problem - won't lock

[Okibi]

As mentioned in another thread i'm also have a problem with the central locking on our 99 NB MX-5.

The central locking will unlock but won't lock the passenger door.

Here's some photos I took pulling things apart.

A small thin screw driver will pop the middle part of the plastic clip outward


The entire clip will pull out


2 more clips on the inside of the door


There's a philips head screw in the middle of the door latch


The outer plastic part can be removed if you pull the latch open






There's a philips head bolt at the top of the door handle


Another on the flat section as the handle meets the door






To adjust the rod you can carefully pop the top of the clip at the latch then adjust the rod, it has ribs on it so it won't slip in the clip


This is the central locking unit removed from inside the door (sorry no photos of removal it's too hard to get a camera in there).










There are 3 wires on the plug in the door and 2 from the plug to the locking mechanism (the black earth wire isn't used).

The difference between lock/unlock is 12volts + or - (Can't remember which way around it is)

The locking mechanism is controlled by a motor and a set of gears that lock/unlock depending on the direction the motor is spinning.

So in my case (it unlocks but doesn't lock) I don't think it can be a wiring fault at the connector because it obviously completes a circuit to spin one direction.

I hooked the lock up to a 12v battery and it locks/unlocks fine, but once connected to my car (free from the door without any connecting rods etc) it will only unlock.

Perhaps in my MX-5 there's a strong enough current to unlock but not to unlock the door. Perhaps it's a dud relay?

[Okibi]

Ok, apparently that electronic component is a "coil" and not "capacitor" because it working in line (series) and not across the motor (parallel).

I think the next step is to look at the amount of amps being sent and check under the dash to see if it's using a relay or the voltage is managed on the central locking circuit board.

[Wuey]

Gee that actuator certainly looks much more complicated than the no-frill J-car cylindrical job.

Two possibilities re your problem:

1. The relay that sends the current to the actuator is faulty, or
2. It could still be a broken circuit in which the locking pulse isn't sent to the relay in the first place. It could also be a faulty triggering alarm/controlling module that sends that signal. A quick check with a multimeter will tell you soon enough.

[Okibi]

Yup as stated it's sending the +-12v to the plug but even when the motor was out of the actuator it didn't spin in the "lock" direction. I'm guessing it has the volts but not the amps to turn over

[crzymx]

Ive got a trouble free fix. Buy a jaycar actuator for the master, and bypass the limit switch. If u dont have the time or resource to fix it this will solve your problem as it bypasses the faulty limit switch and sends current directly to the passenger actuator. You will find this works as the problem is between the lock switch and the plug. So if you bypass it by running the actoator directly into the female socket it will work everytime. Only disadvantage is you lose control of the passenger lock mechanism through key use, however there was no control to begin with as it didnt work!

Furthermore you will probably need some sort of keyless entry to compliment it because the key mechanism isnt setup to send currect into the actuator!

I managed to achieve all this with my alarm install which turned out really good!

[crzymx]

viewtopic.php?f=55&t=34264

check that out for more info.
(dont wanna hijack, but this might help you even)

[Okibi]

Cheers, my next step was going to be testing the lock mechanism in the passenger door with a battery to double check it's nothing in the mechanics of the lock while it's all back together then look at the drivers lock and any relays that it may use.

[Okibi]

Quick question for any NB8A owners with the factory central locking (I can't remember exactly how mine worked before it died).

If you lock the drivers door from the inside, does it lock the passenger one as well?

If you unlock the drivers door from the inside, does it unlock the passenger one as well?

[crzymx]

Cheers, my next step was going to be testing the lock mechanism in the passenger door with a battery to double check it's nothing in the mechanics of the lock while it's all back together then look at the drivers lock and any relays that it may use.

What you can do, is get access to the plug on the drivers door, and test it that way. It is a greay plug and you need to seperate the two halves. Use a test light and poke the terminals on the end that goes straight into the body to the passenger side. By providing a ground, you should be able to activate the lock (lock and unlock). Try this first, if it doesnt work then go onto plan be. I cant tell you 100% how it works because iwas watching my mechanic do it and thats how he explained to me. All i know is that he was poking a test light in it and it was triggering the system.

Quick question for any NB8A owners with the factory central locking (I can't remember exactly how mine worked before it died).

If you lock the drivers door from the inside, does it lock the passenger one as well?

If you unlock the drivers door from the inside, does it unlock the passenger one as well?

Ok simple, yes yes and yes. Regardless of whether u use a key or the switch, it will always lock and unlock the passenger door providing it works in the first place. The only difference is that you cant activate the drivers door from the passenger side!

[Okibi]

Status update,

Pulled apart the drivers door, it actually had a standard "slave" actuator wired in and connected to the rod on the door latch.

There's a separate "switch" built into the door lock that sends a message back to the central locking control box, when I lock/unlock the door I can hear a relay clicking under the dash.

Does that mean the limit switch is working? OR can it still send a signal back and still not be working properly?

As stated previously there were 3 wires in the passenger door but the actuator was only using 2 wires, there's the same 3 wire plug in the drivers door. (I suspect the extra wire in the passenger door is added so that the same loom works on LHD and RHD cars).

[Okibi]

I tried what crzymx said about using a wire to bridge the connector and emulate the door being locked/unlocked, the relay clicked but the passenger door still didn't lock, I temporarily wired up a master actuator to do the same, with the same results.

I suspect the issue is in the drivers door or the pulse strength from the relay.

So why is it all so confusing and different to a standard master (drivers door) slave (passenger door) setup? Because the 99 MX-5 central locking has a separate button to unlock the passenger door, a bit of an "anti car-jacker" feature.

Click the top button and both doors lock.
Click the middle button and the drivers door unlocks, click the middle button again and the passenger door unlocks as well.
Click the middle button and the lights flash (to find your car in a carpark) or in my case it pops the boot (trunk to those Americans who may be reading).

[Abyss]

I am very interested in what you can find because mine does exactly what yours is doing Okibi, it's a 99 and all. Only difference I think is mine also has the Mazda alarm so I am using that fob but it still has all the same problems.

[Okibi]

I have the factory alarm too.

[crzymx]

Have you used a test light to ground the lock and unlock function to see if they work? This is very important, as it will straight away point out how far along your problem is. In the drivers door, theres the plug which im sure your aware of that connects the limit switch setup to the passenger door. There should be a red, blue and black wire i think. Basically one is going to thelimit switch in the drivers door, and the other goes back into the car via the gromet. Now unplug it, and poke a well grounded test light into the ports (red, blue). If your passenger lock is working, each poke will lock and or unlock the passenger door, this means that the problem is the limit switch in the drivers door. Meaning you can do what i did to rectify it.

[mmx005]

i had the same problem, there is a small switch in the drivers door (i think its at the bottom but not sure cos i did it a while ago). i replaced that with an item from jay car and its been fine since.