multiple relays share same common output

phonymike, thanks a lot! I actually thought of using a setup similar to the one you drew there, but like you said, I thought it would be a waste of the on-board relays. And yes, I also realised that the diodes would nullify the grounding capabilities of the other relays. All that's left to do know is to execute the master plan... F R A N S

1985 Mercedes-Benz 230E

320 000 km / 199 000 miles

Full MB Service History

I took another look at my diagram, as well as the one of phonymike's and came to the conclusion that neither my original diagram, nor the one that he proposes, is going to work. The reason is that the switch supplies a negative trigger, whereas the 712T's on-board relays supply a positive 12V. I'm not too familiar yet with relays, but I'm almost certain a relay can't be triggered by a positive and negative trigger at the same time, can it? I concluded that the positive 12V of the 712T's output first has to be converted to a negative trigger. Only then will I be able to use both the switch and relay's output to trigger the relays. This is the diagram that I came up with: F R A N S

1985 Mercedes-Benz 230E

320 000 km / 199 000 miles

Full MB Service History

again this is an assumption since you cannot provide me with more information on the module, but I assume the 'driver's unlock' is actually +unlock, -lock, while the 'all doors lock' is actually -unlock, +lock. what you should do is hook the module up. then read the two outputs with a multi meter. they should both show ground. then trigger it to unlock, one of them should show 12+. then trigger it to lock, the other should show 12+. if this is the case then my diagram will work.

phonymike, here's the wiring harness from the 712T installation manual: I'm almost certain that the common output terminals deliver positive 12V voltage.F R A N S

1985 Mercedes-Benz 230E

320 000 km / 199 000 miles

Full MB Service History

boom that's what I'm talkin bout! now all you need is one relay for the second unlock and you're done, you just treat internal relays like you would normal ones.

phonymike, what about my door lock switch then? Surely I'll have to incorporate at least three additional relays, considering that I'd like priority door unlocking. That last post of yours was a bit vague...what did you mean by it exactly?F R A N S

1985 Mercedes-Benz 230E

320 000 km / 199 000 miles

Full MB Service History

That makes sense, yes! Am I correct when I say that in the normally closed state, the modules on-board door lock relays should then rest at open, i.e. both terminals #87a (H1/6 and H1/17) will then not be used at all? (I only see know that Directed made a printing error with the description of wire H1/6 .) When the coils of the on-board relays are energised, it will switch to normally open, thereby supplying the ground pulse to the other relays, right?F R A N S

1985 Mercedes-Benz 230E

320 000 km / 199 000 miles

Full MB Service History