500ma output

is this enough to trigger the dome light or is a relay needed? i know -500ma is normally enough for trunk release...

If you are connecting to a low current wire it will be fine. 95% of the time, if a car has 4 seperate door trigger wires going to the BCM you can just connect the 500ma output directly to the wire. The BCM is actually what will be providing the power to the domelight. GM cars are usually like this.

On cars with a single door trigger wire, the wire is usually leading directly to the domelight. 500ma will not be enough and you will usually need a relay. Exampes include older Hondas and Subarus.

If you are connecting to a (+) domelight wire, obviously you will need a relay.

You can learn which car needs what by experimenting, and hopefully remembering next time you do another one. If you don't add a relay when one is needed, the domelight will either not turn on, or it will be very dim. There is a slim chance you could burn out the output, but I have never had it happen.

If you want to know about a specific car, post away and I can tell you.

06 cobalt i have to install a alarm on tomarrow and it is - domelight @BCM. do u know on this ride if the trunk will pop without a relay too on a 500ma - output? i have had some cars and some not normally just try it first but if u know off hand that will save time for install, thanx...

You can connect the domelight supervision wire directly to the gray/black LF door trigger wire at the BCM. You will have to diode isolate the 4 door trigger inputs, so make sure you put your domelight supervision output on the BCM side of the diode going to the LF door trigger.

You shouldn't need a relay on the trunk release. The wire you are tagging is just triggering the factory relay inside the BCM, so it will be low current.

Corey, you still installing Ultra? You know me from Sounddomain under a different name.

yea, who is this? i am installing a ultra640 in like 10 mins. i am lucky though it is a 2 door and i have the harness preped already to hook up,thanx for the input...

car is done. only thing i didnt like was i didnt see the C4 plug for the ignition wire so it took a few mins i went to the ign harness.  u are correct on the dome suprevision the gray - BCM,C3 pin A10 tested - even with the doors shut and i waited the delay and light to go out and it reads 12v-...