Alarm Controlled Power Lock

Hi,

I am new here, and need some urgent help. I own an 1996 Alfa Romeo 33 and has Positive door lock triggers. I've connected the Lock and Unlock wires to two seperate relays which are used to reverse the polarity of the alarm pulse. The pulse is negative and so I had to change polarity. The wires are connected to the passengers door locking wires.

Problem is that I've fused both the Lock and Unlock Wires coming from the relay to the passanger door and used 20A as the Central Lock Control is Rated at 30A. Problem is that the fuses keep blowing and I don't want any extra current to reach the central lock control as I already blew it once by mistake.

I didn't use any diodes and used common relays for both the Lock and the Unlock wires. The Image is the one below;

Does anyone know why the fuse is blowing, a 25A works OK but I have a feeling that current is coming back to the relay or that a spike is being produced since I didn't put any diodes. Can anyone Help Please !!

Hi,

Thanks for your quick reply. Infact the wires are quite thin maybe 1mm core wire. There is indeed the central lock control and each time you lock or unlock the doors you hear clicking sounds. I opened the one I blew once and it had like 2 relays inside and the unit which was rated 30A had 5 wires and a ground wire. I guess that this same control is the relay for all the doors. I don't have any lock or unlock switch, if you lock any door all are locked. I don't know why the fuses are blowing though.

Thanks

Keith

Hi,

Thanks for your post, I checked the wires there are 2 in each door, one locks the other unlocks. They are grouped together into one Central Lock Control however its the lock itself that acts as a switch. The central lock weirdly enough works when I give it a positive signal via the alarm system but blows a fuse very often. I used a 20 A fuse on Lock and Unlock wires and used the alarm remote to lock and unlock. The fuses don't blow, however if I forget to close a door right leaving it 1/2 open its blows.  Also my system locks the car 10 seconds after ignition as soon as it locks the doors, the Lock Fuse Blows. I used a 25A and worked fine then ! The vehicle manual has specifically set 20A for the Central Lock in the Fusebox, I am confused however as it could be reverse polarity. It has no lock switch except the lock itself. The control box has 2 relays inside which tick each time you lock and unlock. The control box infact has 5 wires though and a ground. Since by accident I ruined my central lock control unit, I don't want to ruin my brand new central lock mechanism also. Any suggestions ? If it happened to be a negative trigger system how come its working with a positive pulse ?! Another strange thing is that the Fusebox fuse never blows only the in-line fuse connected to the lock/unlock wire blows. This thing has been on my mind for ages as I think I've blown about 30 fuses by trial and error, even blew my Multimeter fuse one time!  I think now I know why Alfa Romeo's are headache's to some! Oh and the central lock mechanism isn't keyless, it still needed someone to rotate the key to open the doors, but any door !

Keith

This is an illustration of the Central Lock Control. The small connection is the Ground the others are harnessed in the car and can't see where they lead however there is a + an M2 an M3 and an M4 at the connection next to it.

Hope its of any use or help.

Keith 

Hi there,

Thanks again for your quick reply. The Alarm triggers the locking and unlocking upon engine run so it can be isolated as its coming from the same wire. The only wires that come out of the locking mechanism are 2 which are blue and blue/black, they are the same for each door. The kickpanel to be honest I don't recall the colours, that I'll check tonight. It could be that the central lock unit is infact the thing that is changing polarity. I'll let you know.

Thanks and Regards,

Keith

Good Mediterranean Afternoon,

I found the wiring and these are what what is coming in the central lock unit.

There is a Constant 12v + voltage (Red Wire) , there are a pair of (Brown) wires which are coming from the doors but register no voltage except when locking, there is another pair of wires (Violet) which are also coming from the doors which registers voltage when unlocking. There is also another pair of yellow wires (Probably for the rear locks) and then there is a thick Blue Wire which Register a + 12 v always when locking or unlocking.

I connected the relays for the 5-wire system but ended up with the locks going up and down constantly, and tried again by connecting them directly to the alarm which ended up in not giving enough power to actualy lock the doors. I rewired the relays to the 2 Blue and Blue/Black wires I found inside the door (Lock / Unlock) these somehow dont exit the door. I connected an SPDT Relay to both the Lock and Unlock Pulse wire and changed the Central Lock Fuse which I realized was incorrectly Protected with a 10A fuse rather than a 20A. Now the fuses aren't blowing anymore and are protected by a 25A fuse. It seems that the locking mechanism on the front doors make a contact with a common + 12V inside the door for each time you lock or unlock, I'll see how long the fuses hold.

Can anyone help and explain how this is happening ? I am literally confused now !

Thanks & Regards,

Keith