Understanding Central Locking

[TheBrit]

Hello to everyone.

I have a problem on a central locking circuit which I just can't get my brain around. I am installing an alarm system into an Isuzu Truck.

The only part of the alarm I can't get working is the cental locking. I will explain my problem below and hopefully one of you clever people can help me out here.

I dismantled the central locking system and checked the circuit. There is a common +12v and then when you press the button to the right, it will LOCK and to the left it will UNLOCK. I observed the connector and +12v is put onto the wire and thus the system will lock, and +12v on the other side will unlock. Now this is where my brain has died.

If I put +12v directly onto the wire which shows +12v when you press the LOCK side of the switch, nothing happens. Also this happens when I do +12v onto the UNLOCK nothing happens. But upon pressing the button physically it will register +12v onto the said wires and work.

Now there are a few other wires in the connector block but printed on the circuit itself is the writing for which wire is un/Lock.

So I ask anyone who may have an incling to help me out here. I would appreciate it.

Thank you

The Brit

 

[fingaz]

Hello to everyone.

I dismantled the central locking system and checked the circuit. There is a common +12v and then when you press the button to the right, it will LOCK and to the left it will UNLOCK. I observed the connector and +12v is put onto the wire and thus the system will lock, and +12v on the other side will unlock. Now this is where my brain has died.

If I put +12v directly onto the wire which shows +12v when you press the LOCK side of the switch, nothing happens. Also this happens when I do +12v onto the UNLOCK nothing happens. But upon pressing the button physically it will register +12v onto the said wires and work.

Now there are a few other wires in the connector block but printed on the circuit itself is the writing for which wire is un/Lock.

So I ask anyone who may have an incling to help me out here. I would appreciate it.

Thank you

The Brit

I had similar problems when I fitted a new alarm to my car.

When you say you have tried connecting +12v to the 'lock' and 'unlock' wires, did you take a 12v from the permanent +12v wire, or did you use 12v from somewhere else? I found that +12v from anywhere else in the car did not activate the locking mechanism but it did when I took the +12v feed intended for the central locking.

If you take the 3 wires (LOCK, UNLOCK and +12V), and physically connect the 12v to the LOCK or UNLOCK, does this make the locking system lock or unlock? On my car (Ford Fiesta), I found that the lock wire went +12v when the car is locked, and the unlock wire goes 0v. The opposite happens when the car is unlocked (unlock wire = 12v, lock wire = 0v)

Neil

 

[TheBrit]

I have 3 wires that as far as I can tell are the ones to the central locking.

1 wire = +12v always
1 wire for lock
1 wire for unlock

When I press the lock button, (its a rocker switch) it shows a 1 second pulse of 12v onto the lock wire, and if i press unlock, I get a 1 second pulse of 12 onto that wire.

When I connect 12v directly from another source, nothing happens.
When I connect the 12v from what I percieve is the permanent 12v to the switch, then the fuse will blow if i hold it on for more than 5 seconds.

It is a very strange system to me. Obviously it is not voodoo magic, but something doesnt seem to fit.

Thanks

 

[JKF1000]

There is normaly a trigger cable for for lock/unlock, if it is grounded the system will lock, and if it is open circuit the system will unlock, this is normaly fed from a switched wire from the alarm system, Karl.

 

[fingaz]

There is normaly a trigger cable for for lock/unlock, if it is grounded the system will lock, and if it is open circuit the system will unlock, this is normaly fed from a switched wire from the alarm system, Karl.

This is another possibility.I have seen central systems that are locked/unlocked with a negative pulse to the lock/unlock wire. If you have this type of system you will probably find that when the door is locked, you should have 12v on the unlock wire. and when the door is unlocked you should have 12v on the lock wire.
If you have this type of system, all you have to do is 'ground' the relevant wire to lock/unlock the doors.

Neil

 

[TheBrit]

Sorry for the late reply, I am going to get some more readings and a couple of photos of the door lock system when I have time.

Thanks for the input so far, but since there are quite a few wires, I will try and get more measurements.

But there is definately 12v onto the switch wire for lock when its pressed and 12v on the unlock wire when pressed, only for 1 second though.

Thanks so far

 

[Boncuk]

The system can be overridden by connecting the external power source correctly.

As far as I could read the negative terminal of the power source wasn't mentioned and therefor disregarded for testing.

The rocker switch for locking and unlocking has normally three positions: center position, lock and unlock. In the center position neither lock nor unlock should be energized.

Leaving the switch in the neutral (off) position and using an external power source directly on the lock/unlock wires the negative terminal of this power source must be connected to the car chassis. Otherwise nothing won't work.

Boncuk

 

[fingaz]

Hiya,

I'm not sure what model Isuzu you have, but I have managed to download this wiring diagram which I think is common to a few Isuzu's.

If yours is wired like this, then applying a 12v feed to the lock/unlock wires is not the way to go. Personally, I would take the 3 wires which connect to the switch, and use these (it depends on whether you can connect to these physically ie. design of the switch)

Hope this helps.

Neil

 

[Mickster]

The 'common' symbol in Fingaz' schematic denotes a Negative (Ground) signal is required.

Assuming this schematic applies to the vehicle concerned:

A simple test....leave the switch installed and probe the Lock & Unlock wires in turn, with a standard automotive test light. You'll likely find that the central locking works as intended, since the ground path is completed through the test lamp filament.

HTH.

 

[TheBrit]

Thanks for the diagram I will work on it early next week.
I will then be able to tell if it is the same or not. Briefly looking at it, it looks good.
Thanks for finding it, I was spending a long time scouring the net looking for help.

Lets see if i can work out what I am meant to do now

Time to bring in my City and Guilds 224 qualifications.....

Thanks Again

 

[Eclipsed]

First you should determine if the lock/unlock wires you found rest at ground(ground when switch is centered).Or when you move the switch to unlock, and you have 12v at the unlock wire, check to see if you have ground at the lock wire, or vice versa.If you find one of the above to be true, you have a reverse polarity type, sometimes called 4 or 5 wire reversing/alternating, and you will need to add spdt relays.

Automotive Power Door Lock Types, Determining Switch Types

You should be able to find the proper diagram for your vehicle on that site as well

 

[squiz]

keyless entry

i have a 93 trooper citation,ive bought a remote keyless entry kit.(rightclick)..i have had the system locking and un locking...however...it doesnt do it everytime...the system will flash when i press lock but the doors dont operate,if i then press unlock the doors lock..then if i press lock the system flashes as if its working.then i press unlock and the doors unlock. also the alarm will sound when it feels like it when its locked......i have wired (negative pulse) at the C/L control box in the passenger side(left) kick panel.
any ideas where i have gone wrong? do i need to have other wires conected? the info from right click is far from helpful..and all this is before i have figured out to wired the turn signals to flash when locking and unlocking.
i hope some one can help me i feel ive wasted my money on this.

many thanks in advance

squiz

 

[fingaz]

Hi,

If you had the system working, but intermittently I would think you may have a faulty connection or a short on one of the wires. If it was me, I'd disconnect the whole thing and start again. Make sure all of the connections are clean and well insulated, and make sure there is no damage to the insulation on the wires. Don't just undo all the wires and reconnect them to where they were before, remove the whole thing and look at the diagram to see how it should be connected.

Hope this helps
Neil

Edit: whenever I have fitted alarm/central locking kits I ALWAYS connect it into the drivers side. Not sure if this would make any difference.

 

[squiz]

keyless entry

thanks neil, i will stat again i think,im now waiting on reply from phone call to right click,any ideas would i need any other wires connected to sort the the alarm out? its as if it isnt disarming but the doors are open.is it all one curcuit?as in when doors unlock the alrm is also turned off through the same wires?.

the drivers side is a tad conjested with wires etc,(unless it has to go this side to be wired in front of the anti theft system?).also the manuals for the troopers i have seen all say that the 12v constant supply is to the passenger door.

 

[TheBrit]

Wow its been almost 4 weeks since I lasted posted a thanks about the wiring diagram.

I have finally got time today to have a look at the system...

Will let you knowledgable people know if i have a problem or not.

Thanks again

TheBrit

 

[squiz]

well guys i have my keyless entry working,wires notshown on the diagram not connected,quality information supplyed!.....how ever when i unlock with the remote the alarm goes off,it turns off when i put key in lock. any ideas?

 

[taurus3]

usually memory + indicates constant +12volt supply.

 

[Eclipsed]

well guys i have my keyless entry working,wires notshown on the diagram not connected,quality information supplyed!.....how ever when i unlock with the remote the alarm goes off,it turns off when i put key in lock. any ideas?

There's a switch mounted to the back of the lock cylinder in the door.Probe the wires and find the one that switches(to ground) when you turn the key to unlock.Some keyless units will have a disarm output, which will need to be connected to the wire at key cylinder, if not, you can use the unlock wire coming from the keyless unit.You will need to use 2 diodes(1n400x) to isolate it from the vehicles door lock circuit.

 

[squiz]

hi eric,thanks for your reply...how ever...im no wizard with electronics so i have no idea how you mean to connect the diodes.......the keyless entry system is a rightclick 27b plus.....i have all the wires connected that i was instructed to and this works better than how i had it before...there is a wire that apparently connects to (horn) according to the diagram and instructions.....all my connections have been made at the central locking control box.do i really need to be inside the door?

 

[Eclipsed]

Inside the door is just the most reliable way of finding the wire you need.I'm not sure what a trooper citation is, but if it's similar to a regular trooper, you can use the Brown/Red wire in the Driver's Kick Panel or Orange/Black at the Theft Module.The correct wire will switch to ground(-) when the door key cylinder is turned to unlock.

As for the diodes, you need 2 of them.1n4001 will work fine and you should be able to find them at any electronic parts store.

First, cut the unlock wire you hooked up previously.
Then you need to connect the ends closest to the white band of each diode together and that goes to the unlock wire coming from your keyless unit.
The remaining ends(farthest from the white band) one will go to the unlock wire at the vehicles' door lock module and the other will go to the wire explained above.

Hope that isn't too confusing, wish I had an easier way of explaining it.