multiple relays share same common output

it'll only create a short circuit if + touched - in which case your fuse (should have a fuse) will blow. why use 2 relays? I've seen it done before, basically if you need more power. each relay can typically handle 30amps, so if you put 2 relays side by side (parallel not series!) they can handle 60amps together. I don't know if this is recommended though, as they have solenoids (big relays, not door poppers) that can handle like 100 and mor eamps.

if both relays having the same output terminal, and also have the same input terminal (12 volts) then basically either relay can power the device, which is redundant, unless one relay is triggered with a - pulse, and the other relay is triggered with a + pulse.

did any of that make any sense? maybe I'll whip up a drawing if it helps.

looking at your diagram, neither door will unlock, only the passenger will lock, there's no ground path in either direction for the driver's door cause you're blocking it with diodes. I don't like the idea of diodes running anything more than a signal, like to a relay either. anyone else have any qualms about designing a circuit that assumes that the lock and unlock state will never happen at the same time? also I don't see enough information. is the switch an aftermarket switch that could possibly be rewired to 12+? are there any factory relays that could help assist this situation? because looking at this, ignore your switch, I just figure hook up the driver's side actuator to both "driver's unlock" and "all doors lock" as normal. then using a relay, have 87 and 85 at 12+, 87a at ground. 30 would go to one side of the passenger actuator, and the other side of the actuator would go with "all doors unlock" assuming this output on the 712T rests at ground.

can you post the instructions for this module? because as is it looks like a silly bitch to wire in an external switch. as is it looks like it'll power the driver's side door no problem, and adding 1 relay will add the passenger's door no problem, no diodes. maybe someone else can help but I don't see enough information.

take a look at your diagram. when the unlock is pressed from your switch, it it triggers the first relay giving the driver's door a nice 12+ on the blue wire on the left. where does the driver's actuator get a ground? the third relay is resting at ground, however a diode there blocks the ground (the cross line that the arrow points to is the cathode of a diode, ground can pass through the cross line) as well does the other diode coming from the 712t module. see it?

again based on the information you've given, I think the easiest way to do this would be with three relays, no diodes. if this is anything like my alarm, we will use the 'driver unlock' as a ground output to unlock a new driver relay. the passenger unlock output will be the ground for a new passenger unlock relay. then the 'lock all doors' will be used as a ground output to lock them both.

all relays have 87 and 85 going to 12+. all relays have 87a going to ground. 30 on the first relay goes to driver's actuator, 30 on the 2nd relay goes to passenger actuator, and 30 on the third relay goes to the other side on both actuators. at which point your unlock switch and 'driver's lock' on the module get tied together and go to 86 on the first relay. your 'passenger's unlock' on the module go to the second relay. then the lock switch and "lock all" go to the third relay.

the two door relays rest at ground, so when the lock both doors relay gets energized, it sends the 12+ to the acuators to lock them both. otherwise the lock both doors relays rests at ground, so when you energize the driver or passenger relay, they send 12+ to unlock the actuator. it's just a waste of the built in relays in the 712t module but oh well.

ain't it pretty? you do need 1 diode to isolate the driver's and passenger unlock, while still allowing the switch to do both. or leave it out it's up to you. there's no need to worry about 'feedback' or blowing fuses. if you somehow unlock the doors while locking them, the relays stay in a rested state at ground or 12+ so it does no damage.