NB Central Locking not functioning

My central locking was working fine yesterday, but today when I went out the lights flash when I press the button on the key fob but there’s nothing happening with the central locking - not even a sound!

The central locking works fine with the key - so I don’t think its the actutator.

We did have a lot of heavy rain early this morning - it woke me up - & I had some coolant boil over out of the expansion tank yesterday so I’m wondering if its gotten a circuit wet??? The central locking was working normally after the coolant boil over.

Central locking is with the Cobra alarm system.

Any idea what to check?

I’m kind of thinking maybe a fuse or a relay???

Is it a 1.8is it will be if it has abs brakes.

I have a 2005 NB 2.5 1.8

My fob stopped communicating with the keyless entry for no reason. I replaced the battery in the fob and then re-programmed the fob as per the instructions below.

Everything started working again and has been fine since.

Simples !!!

To Registering Keyless Entry Transmitters NB & NC

  1. Shut all doors and remove key from the ignition switch
  2. Open drivers side door
  3. Insert key into ignition, switch ignition on, then off then remove key 3 times.
  4. Close then open drivers door 3 times (all doors should lock then unlock)
  5. Press unlock button twice on the transmitter (doors lock then unlock to confirm)
  6. Press unlock button twice on all other transmitters to be registered to the car (doors should lock and unlock to conform each transmitter registered)
  7. Switch ignition on to cancel set-up mode.

Check the 10A ROOM and 15A METER fuses for starters (Fusebox in the dash) and see if they are O/K.These feed the keyless unit, though if the fob boot release works then presumably at least one fuse is O/K. That should indicate the keyless unit is O/K, but not certain at this point.

The door lock timer unit works off the 10A LOCK fuse, but if you can lock and unlock the door locks with the key, then I have to assume that’s O/K. Also the ROOM fuse is involved, but if that was O/K then don’t worry about that.Then there’s the 15A ENGINE fuse, offhand I can’t remember where that is - sorry.

No relays involved AFAIK, so if the fuses are O/K then either part of the Keyless Unit, or the Door Lock Timer may be faulty, but on wiring diagrams these are empty boxes, so no idea how to check them, they either work, or the don’t.

Thanks guys - I’ll have a look at the fuses but probably not till tomorrow - feeling a bit delicate after last night.

Yes its a 1.8 l

Mike - I omitted the obvious - the battery in the fob, but you can easily check that if the boot release button opens it. ( assuming it’s not stuck, like mine is!) I can hear the solenoid working anyway, I need to treat the rubber seal, when I get a roundtuit.

Pretty sure the battery in the fob is OK as the alarm turns on & off - just nothing happens with the central locking.

Checked the fuses - all OK

Took door card off nothing there that looks out of place, no breaks in wires.


So looks like its the re-registering of the key fob next as Dipstick suggests - might wait & get anotehr key fob & register that one as well - 2 keys & only one fob - so makes sense (to me at least)

Replacement fob £60. Decided I would stick with one.




They’re trying to rob you !


Cobra one http://cobracartech.co.uk/cobra-replacement-key-fobs-cases/147-key-fob-replacement.html

There’s a few similar to the one you lineked to on ebay http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1311.R4.TR4.TRC1.A0.H1.Xmx5+key+.TRS0&_nkw=mx5+key+fob&_sacat=0


Cobra ones on ebay http://www.ebay.co.uk/sch/i.html?_odkw=mx5+key+fob&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xmx5+cobra+key+fob.TRS0&_nkw=mx5+cobra+key+fob&_sacat=0


Think I’m just about to spend a couple of quid on ebay - but non Chinese ones !

May work on your model. Don’t work on 2.5 with rolling codes.

Rolling codes on the MK2 special editions - well so the owners manual says :slight_smile:


Might just splash the £39.99 & get the genuine one from Cobra though, only £10 more than the ebay ones, £10 not much for peace of mind IMO

The self same thing happened the other day with my Mk2. The central locking failed to open when I used the key fob. I’ve a Cobra 7777 alarm fitted. Fitted a new battery, no difference. Tried to open driver’s door, alarm activated. Fitted another new battery, alarm activated. Took a closer look at the key fob and found what resembled a grain of black rice. It was one of the minute locating pins. SuperGlued back, replaced the gubbins, no difference. Alarm activated. By now I must be really irritated the elderly nextdoorneighbour. Perhaps I could disconnect the alarm. Unfortunately the thick wiring harness doesn’t plug in. Sent off for a replacement key fob casing. If that fails, it’s another key fob. If that fails…?

(Next day) Replacement key fob shells arrived, I swopped the gubbins over to the new shell and…zilch. Next step is to order a completely new key fob, damn!!!

(The next day) Nope, she turns over but won’t start. Now where’s the number of thet mobile mechanic?

I sent off for a new key fob - about £49 - and read the re-programming instructions in the Cobra handbook. I just KNEW that things wouldn’t go right, and they haven’t. I insert the key into the driver’s door lock, open the door, and the alarm activates. Then it stops. I quickly enter the car, insert the key into the ignition lock, switch the ignition on and off three times (following the instructions, and the the alarm goes off. Then it stops. I repeat all these steps and the alarm activates. This must be driving my neighbours NUTS, it certainly driving me nuts. CobraCarTech doesn’t have a telephone number so I cannot speak to a human being so I’ve emailed them to discover what I’m doing wrong. If there are any MX-5 owners local to be (Bearsted, Kent) who could advise me or even pop around, I’d really appreciate it. My car has now been off the road for a week now and my patience has it’s limits.

(Later) I received a reply from CobraCarTech who advised me that they are retailers only of Cobra alarms and advised me to telephone Vodaphone Automotive on 03331-222-222, Press Option 2 for Customer Support, then Option 1 for Vodaphone Automotive Tracking, then Option 4 to speak to Technical. This I did (eventually) and the advise was “Ignore the constantly irritation of the alarm going off and carry on switching the ignition key on and off, then the miniscule red LED dot on the key fob as described in the handbook and using the PIN number”. Oh well that’s tomorrow morning’s job. I’d better waiting until the old lady next door goes out.

(Much later) Well this sorry saga continues. I went outside this morning with the ignition key, zapper and instruction book, bouyed up with the advice from Vodaphone. The old lady had gone out so I slavishly followed the handbook instructions only the miniscule LED failed to light up and yes, the alarm woke any sleeping neighbours. Another phonecall to Vodaphone. “Do you have a touch key in a recepticle to disarm the alarm. You cannot reset the alarm until you’ve DISARMED it first. I recommend you get an auto electrician to take a look. The Cobra 7915 alarm is an old one and it may have a wiring fault”. So that’s the next step, call out an auto electrician. Car off the road for about ten days now :frowning:

(Even later still) The auto electrician arrived and baffled me with jargon. Basically there could be a fault with the alarm/immobiliser itself as these were installed by the original dealers. The new ‘Zapper’ failed to operate as the system needed to be de-activated before re-activating it. It still failed to function. In the end he entirely removed the alarm system and immobilser so the car has reverted to a simple key to unlock/lock the doors. The car won’t now start and he recommended giving the battery a thorough charge to see if it will spring into life. Let’s see if I can get a refund on the £49 zapper. Of the bill with the call out charge, removal of the alarm/immobiliser and system check is an eye-watering £366. Jeez! Why do I think she won’t start once the recharging is complete?

(Later) I was right, she won’t start. Mobile mechanic then?

So with the car being off the road for about three weeks and it failing to start after the auto electrician had removed the alarm I went out the other day and low and behold, she started. What a relief. I can only assume that the fuel injectors were flooded (I’m a carburettor person). So off to a drive to Dungeness yesterday and once again she is as sweet as a nut. phew!