Hi Guys

I need some help understanding this circuit. By the looks of it, its a simple relay driver with a timer. But for some reason the actual relay does not work when power is applied to the appropriate pins.

This is from a wiring diagram of a Mazda Protege car. The timer is used (i believe) to time the amount of power given to the door lock motors and to reverse their polarity depending on the lock/unlock action.

 

Sorry friend, I dont see a timer at all.

This is a simple DPDT relay circuit the wavy lines are fuses, and the zigzag lines are resistors.

It may help to redraw it with out all of the >> connector codes and such to see it

It only contains 4 items besides fuses.

Battery, lock up/down switch, relay, and the lock motor.

Depending on the position of the lock switch, the relay operates the corresponding switch to operate the motor in a positive or negative biased operation (up or down-clockwise or counterclockwise)

 

The power door lock timer relay box contains, 2 transistors, a couple of resistors, 2 capacitors and 2 diodes.

I'll try to get the values for these compoments from the actual relay box.

Its a timer because the door lock motors can not be given continuos power. It requires a momentory power to lock/unlock with reversed polarity.

 

See the switch in the power door lock motor? Looks like a mechanical limit switch. Quite a clever circuit.

 

mustu is right the box contains of simple delay circuit , it depends on the value of capacitor and resistor inside of it. when one of the transistor is on (when capacitor is fully charged) the other turns off (capacitor is dis-charged).

 

Guys in order to understand the circuit better I build one!... virtually.

I was able to understand a little bit more on the circuit after i built it online on a virtual simulator. To see it working goto http://www.falstad.com/circuit/

In the Java applet that pops up goto File->Import and copy and paste the following info. (copy the lines between the ***Begin*** and ***End***)

***Begin***
$ 1 5.0E-6 19.056626845863 75 5.0 50
r 496 192 608 192 0 7500.0
c 496 256 608 256 0 2.2E-5 0.6515777830983401
c 496 304 608 304 0 2.2E-5 9.590836246272403
r 496 368 608 368 0 7500.0
r 496 192 496 256 0 5100.0
r 496 304 496 368 0 5100.0
r 400 80 400 144 0 680.0
w 480 464 480 432 0
r 448 512 448 464 0 680.0
w 448 464 480 464 0
w 400 80 480 80 0
w 400 144 480 144 0
w 448 512 480 512 0
w 448 512 368 512 0
d 368 512 368 432 1 0.805904783
w 400 80 352 80 0
d 352 80 352 176 1 0.805904783
r 368 432 368 384 0 1000.0
r 352 176 352 224 0 1000.0
w 352 224 496 304 0
w 368 384 496 256 0
w 608 192 608 256 0
w 608 256 608 304 0
w 608 304 608 368 0
g 608 480 608 512 0
w 352 80 272 80 0
w 368 512 288 512 0
R 128 304 128 208 0 0 40.0 12.0 0.0 0.0 0.5
w 512 144 608 144 0
w 608 192 608 144 0
w 608 368 608 432 0
w 608 432 608 480 0
w 512 432 608 432 0
178 480 464 576 464 0 1 0.2 4.571087518520204E-18 0.05 1000000.0 0.02 20.0
w 480 464 480 496 0
178 512 80 528 80 0 1 0.2 5.337625497454221E-7 0.05 1000000.0 0.02 20.0
w 480 144 512 128 0
w 480 80 512 112 0
S 128 304 272 304 0 0 false 0
w 272 80 272 288 0
w 288 512 288 304 0
t 496 368 496 432 1 1 0.6054650082891723 0.6057137665604939 100.0
t 496 192 496 144 1 1 -11.61216779733556 0.38782750546328265 100.0
w 288 304 272 320 0
x 131 109 181 115 0 24 NPN
***End***

When running the circuit and toggling the switch you will see that the relay energizes for about 250ma and de energizers... (exactly what is required)