Building a body control module for door locks and lamp control.

#1
I am building a "Custom" Body Control Module for my 67 C10 truck. I am using an aftermarket keyless remote relay with a simple two states, "On" or "Off".
I’m a retired ASE Master Tech, I wish to keep parasitic drain low when the vehicle is locked and shut off. The keyless relay “On” tested at 30mA, while the control side is capable of 15A.
Function #1; Lock signal on 1 sec, then off. With keyless relay off, Un-lock signal 1 sec, then off. Using circuits I’ve seen on this forum have given me ideas for a 100uf to pin 2 with 10k resistor to ground, thus on, then off. I am using one relay for power to lock, while the other is “NC” to ground.
Question? When the supply power is off, how do I trigger second 555 to operate relay #2 to provide un-lock signal. The time off is anyone’s guess as the vehicle sits. With a 555, can it be triggered by sinking to power? I have seen where and LED to LRD could be used to trigger when the light is lost. I am concerned about overheating a 555 depending on its state of trigger.
Function #2; I want to trigger certain lamps “On” and blink twice, then shut off.
I have seen the suggestion of using a “Off delay time delay relay”. My light control circuit is using a 555 with a n-channel MOSFET and diodes in series with each lamp circuit to prevent back feed when normal light functions on vehicle are used.
I enjoy the challenge as the brain is a muscle the needs exercise. It is boring doing the same thing each day.
I have strong electrical diagnostics skills, but this is first time building electronics. Fortunately, I inherited my Grandfathers small part bin with hundreds of components including “And”, “Nand”, “Or” gates, quad drivers and many more as he got his Masters Electrical in 1932, then was in the Army Corp of Engineers and spent 7 years in the 60’s as chief electrical inspector for the Meck Island minute-man missile site in the Marshall islands.
Any suggestions welcome. We can tackle one thing at a time. Thanks!
 
#2
Question? When the supply power is off, how do I trigger second 555 to operate relay #2 [...]
If you mean that the power to the 555 is off, then you can't of course.


With a 555, can it be triggered by sinking to power? I have seen where and LED to LRD could be used to trigger when the light is lost.
"Sinking to power"??
Wild-guessing here, but do you mean to ask, if the 555 can be triggered by having pin2 pulled to Vcc?
If so, no, but a small signal transistor can be used to "translate"


I am concerned about overheating a 555 depending on its state of trigger.
As long as you stay within its operating parameters, you shouldn't be.

I'm not sure I got it right, but I think that you want to make a sort of interface between receiver and relay(s) and flashing your turns flashers or similar twice at each actuation - and consuming the least amount of power while idle?
If that's the general idea, you'd be better off with a small microcontroller (eg the size of a 555). They can spend most of the time in a sleep state consuming next to no current and it'd be easy to have different flashing patterns on open and close.