MG TF strange sound from new door locks?

HI

I'm a new TF owner and when I got mine it used to have an issue with door lock, when locking with the remote. After pressing the remote it would honk, but then after unlocking and locking again, I would get the 3 blinks. From time to time it would make the 'grrrrr' sound, which after dismantaling one of the lock I found was the deadlock part being broken inside of the lock.

I decided to get new locks for both doors. After replacing then and locking couple of times, I still got the grrr sound right after it tries to lock. When I took one of the locks out, and tried to lock (i have pushed the latch in, so the car would think, the door is closed) it made the sound and then I could not push the door opening lever (white one). I think that somehow the motor doesnt know where it is and it tries to lock/unlock twice. Could this be the case? and does anyone know what could be the solution?

I got the lock from rimmerbros, so they should not be damaged, could they?

Here is the issue in video format ( the grrr sound can be heard from 00:15):

I've had this on my TF also with a brand new lock but it only does it when the car has been stood out in the sun for some unaccountable reason . It locks and unlocks so I'm going to leave it .
John

Does it always lock and unlock from the first time?

Because for the when it starts making that strange sound it get into a state where I have to lock/unlock multiple times until it stats working again.

Well yes it locks fine . I initially thought that there was a fault with the latch so , I removed it and took it apart to check for the dreaded broken plastic pin but it was fine so I just think it's part of the F , TF ' thing ' with the locks .

I did some more digging and decided to check the SCU, since I read that there are usually issues with it. After opening it, I think I might have identified the issue or some other issue.

Did anyone experience this issue before, where the red thing would blow up? and anyone know what the red things are and if they have any new version of it, that I could buy? since i tried googling the model but didnt find anything except couple ebay listings

You need to contact Paul Brown ( Technozen ) who is a master at repairing the Pectron bcu . Just Google Technozen and contact him in Brighton .
or go to www.technozen-electronics.co.uk

Hi there,
the red thing is a Varistor -its job is to offer protection to excessive transient voltages by offering itself up and sacrificing itself by becoming short circuit.
There are 2 relays either side of both varistors -the most likely cause of the rattling is the inside one (super lock relay) -the edge one is the Central Locking relay.
They are notorious for going open circuit across the relay coils -but first they go intermittent and arc over -this causes the relay to bounce on it contacts and effect the super lock motor in the door lock.
I believe that many door locks have been replaced for the wrong reasons
The PEKTRON devices are the bad ones and need to be replaced with the more modern units.
If all your relays are original get them all replaced in one lot -you will eventually get more going faulty.

link to relays--https://www.highliftmedia.com/mg-rover-scu-pektron-bcu-relay-faults-and-replacement-locations/

I have not seen the Varistors go like that -so its one to watch for ..

Mike

Thanks for that explanation, Mike. :clap:
That's a new one on me...

Incidentally David, the super lock internal motor is very fragile compared to the door lock internal motor ( inside the door lock assy)

The super lock motor is partly a printed circuit mounting -this part fails and the super lock is stuck on (probably a safety feature)
The superlock motor is fed by 2 wires and an earth -these 2 wires are fed by 12volts which is reversed by the SCU relays depending on whether you are locking or unlocking .This leads to the possibility of firing 12 volts up the superlock side of the door lock to unlock a failed door lock, I did that- it was awkward getting the passenger door internal s off while the passenger door is locked --but doable without damaging the door cards.

Mike

www.technozen-electronics.co.uk