rear defroster info

I dont really understand the whole rear defroster thing. I know you can turn the rear defroster on with different remote starters. But what is the typically way on how to find the correct rear defroster wire? Then I read something in the program settings about pulsed and latched. What does that mean? Also, on the DEI units.....it says (-) output. I tested the defroster wires. Found one wire that rests at ground, press the switch and it switches to 12V. Is this the right wire? Do I need a relay to switch the (-) polarity output to positive. Im a little confused. I never really bothered to hook up the rear defroster switch, but would like to learn how its done.

Thanks.

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hi,
finding the right wire is dependent on the system used to control the defroster relay. some have the defroster relay incorporated in the switch, others the relay is external.
if the relay is internal, the output is probably positive. this requires a relay on the output to invert polarity of the remote start output.
if the relay is external, the control signal maybe positive or negative.
the output of the remote start might be able to be connected directly to the defroster switch if negative...checking the current of the control circuit is advisable.
the pulse or latching depends on the switch and relay control of the defroster circuit.
an internal relay defroster switch would use a latched output, i.e. defroster activates for set period of time.
an external control could use either. the switch might mechanically latch on requiring a latched output, or be a momentary contact requiring a pulse. the momentary pulse external relay style usually incorporates a timer as described above.
the defroster output (aux output) of most remote starters are typically 200 to 500 mA... not able to connect to a high current circuit, such as a defroster directly.
hope this helps.
mark

The "only one size fits all" method is to take the hot wire window feed itself which is the wire going to the rear which goes to 12v+ when you turn on the HRW (=heated rear window). The front end on a modern vehicle especially with climate control has too much to go expensively wrong if you interfere with it.
Take an aux output, through the bitwriter programme it for 10 minutes timed output then;
aux to relay 85
fused at 20amps to 86 and 87
front side of car to 87a and window side to 30.
Diode 1N4004 across 85 and 86, band to 86.
This doesn't affect ANY of the other vehicle systems, nor will it feed back to any processors.


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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.