BCU - how to determine locked/unlocked state?

goltho · 4th November 2018, 17:01

I need to be able to distinguish electronically between locked and unlocked states. More precisely, if the car is locked, I need to be able to ignore subsequent lock requests. Similarly, if the car is unlocked, I need to be able to ignore subsequent unlock requests.

I understand how the BCU receives its inputs in order to activate the various components included in locking and alarming (mainly via C0660). As far as I can see, the inputs are generally momentary earths.

Context
I've fitted a manual boot switch to the underside of the plinth and it works fine. When pressed, the switch closes and earths the GR wire between the interior boot switch C0221-2 and the BSU C0660-48. This then causes the BCU to send a timed 12V signal from C0660-2 to the boot actuator, opening the boot. In other words, it does exactly the same as the interior boot switch. Simples.

However, I now have to interrupt/keep the earth circuit open from the new switch to C0660-48 when the car is locked, to avoid the boot being opened/the alarm being activated/my stuff being nicked.

A mechanical latching relay would be fine if there was a guarantee that when the car's locked, no other signal could be sent to the BCU except an unlock one. (I could for example, trigger the relay from a door actuator if it was only sent power on the first Lock signal or the first Unlock signal.) This however is impossible (to guarantee) as I can press the lock button as many times as I want whilst the car is locked. So the relay would open/close/open/close to its heart's content regardless of which button was pressed.

So are there - BCU or anywhere - two outputs (going anywhere) dealing separately with lock and unlock? That would solve it easily. If not, what other methods are there to detect locked or unlocked state?

Sorry it's a long one.

Dougie.

4th November 2018, 17:01	#1
goltho Can't help myself Rover 75 CDTi 2005 Join Date: Jan 2018 Location: Lincoln Posts: 888 Thanks: 469 Thanked 150 Times in 113 Posts	BCU - how to determine locked/unlocked state? I need to be able to distinguish electronically between locked and unlocked states. More precisely, if the car is locked, I need to be able to ignore subsequent lock requests. Similarly, if the car is unlocked, I need to be able to ignore subsequent unlock requests. I understand how the BCU receives its inputs in order to activate the various components included in locking and alarming (mainly via C0660). As far as I can see, the inputs are generally momentary earths. Context I've fitted a manual boot switch to the underside of the plinth and it works fine. When pressed, the switch closes and earths the GR wire between the interior boot switch C0221-2 and the BSU C0660-48. This then causes the BCU to send a timed 12V signal from C0660-2 to the boot actuator, opening the boot. In other words, it does exactly the same as the interior boot switch. Simples. However, I now have to interrupt/keep the earth circuit open from the new switch to C0660-48 when the car is locked, to avoid the boot being opened/the alarm being activated/my stuff being nicked. A mechanical latching relay would be fine if there was a guarantee that when the car's locked, no other signal could be sent to the BCU except an unlock one. (I could for example, trigger the relay from a door actuator if it was only sent power on the first Lock signal or the first Unlock signal.) This however is impossible (to guarantee) as I can press the lock button as many times as I want whilst the car is locked. So the relay would open/close/open/close to its heart's content regardless of which button was pressed. So are there - BCU or anywhere - two outputs (going anywhere) dealing separately with lock and unlock? That would solve it easily. If not, what other methods are there to detect locked or unlocked state? Sorry it's a long one. Dougie. Last edited by goltho; 4th November 2018 at 18:21..