Calling PMP experts - explain this

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NerdyMate

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The set up: DR900S-2CH and PMP (installed by local garage who normally installs DashCams in October 2018) in a XC60 Mark II (new 2018)

The weird behaviour:

1 . If the PMP Voltage cut off is set to 12 V, the DashCam starts (i.e gets power) when the doors are unlocked and starts recording. With the PMP is OFF, it powers down a few minutes after the car is locked as expected (my normal set up)

2. Now, I changed the Voltage cut off to 12.5V on the PMP. So now the DashCam does not start on unlocking the door, but does so when the engine is started and powers down a few minutes after locking the car with PMP OFF as in 12V mode as expected. I have further checked that the Voltage of the battery is 12.66 and the DashCam does go into parking mode as expected when PMP is set to ON.

I like how it works in in the 12.5V mode ( i.e Dashcam starts with engine start rather than door), but surely something is not quite right with the PMP ?Voltage leak when set to 12V?
 
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Are you saying it's weird that the dash cam is turning off only after a couple of minutes after car is shut off, even when PMP is set to off?

If so, your vehicle must have standby timers for ACC fuses so that they only turn off after a little while when the car is off. This is common for BMWs.
 
NO. The weird behaviour is different start up when the PMP cut off is set to 12.5 and 12V - that is on door unlocking at 12V and engine start at 12.5V

NB I have edited my OP to make it clearer
 
Not weird at all. For the PMP to switch on, it needs a voltage of about 0.25V higher than the set cut off point. So with 12.5V set, it needs about 12.75V to switch on, and your reported 'door unlock' voltage of 12.66V is below this threshold. Simples. :)
Read all about it
 
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Ah ... So if my battery voltage is say 12.8, then it would start on door unlock even if the cut off voltage is 12.5V. Correct?

Why would power delivery to the DashCam depend on the cut off voltage though?
 
1. Correct.
2 Why wouldn't it?
If you have the cutoff voltage set to (say) 12.5V then you want the cam to switch off when the yellow wire (permanent 12V) drops to 12.5V. So it should be pretty obvious that if the voltage is at or below 12.5V the PMP should not start the BV and discharge the battery even more.

The design of the PMP is such that the yellow lead has to be about 0.25V above the cut off before a nominal 12V applied to the red lead will switch it on (it's called hysteresis).

You will need to ask BV why they decided on this design philosophy. But it seems pretty sensible to me
 
I guess I need to ask why you would tie into power supply that only goes active when the doors unlock? Is not the intent of the PMP to have an always on source that is monitored for time or voltage.. as well as an "on" only when the ACC circuit is active.
 
Correct.
But the OP obviously has the Red wire connected to a supply that becomes live when the doors unlock rather than the 'conventional' ACC ignition switched supply. Providing the Yellow wire is connected to a permanent 12V supply, it will work properly as designed, except it will switch on when the doors unlock rather than when the ignition is switched on.
But I don't think that the difference really passes the 'so what' test, which is why I didn't question it. :)
 
I would like it that way, but I think this how it works on Volvo's. A few others have told me (power on door unlock)
 
Does the ignition come on when door unlocks? I doubt it.
So find yourself a 12V point that comes on with the ignition (there must be one somewhere) and connect the Red wire to that instead of to where you have it currently connected.
 
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