2nd starter general knowledge

thanks. just trying to gather info for future use. IF an alarm or RS has a second output that is cofigured for 2nd starter and is same polarity as the vehicle...then no relay right just hook up and go? I keep seeing a relay for like toyota etc. is that only if module has primary starter only.The RIGHT way is the ONLY way.

Many times the 2nd starter output is a low current (-) output. If so, a relay will be required.Kevin Pierson

most units on the market have the following (+) outputs on its primary (larger gauge harness)

start 

ignaccparking light5th relay (can be configurable for acc, ign, or start)and two 12v (+) inputs.

the toyota requires a relay onlybecause it is a postive start wire, whereas the unit outputs a negative. Therefor you must use a relay to convert the polarity.

if the car has a negative start, as KP mentioned, it is often 250ma up to 500ma depending on brand. You should always rather be safe than sorry, so just wire up a relay even if it is a low current system. If using a relay,  remember to use a diode across the terminals to prevent backfeed on the unit which might damage the output.

Ted

2nd Year Tier 1 Medical School

Still installing as a hobby...pays for groceries

Compustar Expert

tedmond wrote: If using a relay,  remember to use a diode across the terminals to prevent backfeed on the unit which might damage the output.

All reputable manufactures include the diode assuming the low current output will drive a relay. I've never seen a unit (even cheap ones) that don't have the diode built in. The typical output section of a remote start / alarm contains a driver chip that has multiple Darlington transistor arrays with all required resistors and diodes built in. Here is a datasheet for a very common driver chip: http://focus.ti.com/lit/ds/symlink/ulq2004a.pdf and the schematic is on page 3.Kevin Pierson

Yes Kevin but for how long it takes to install and its cost I'd rather add one, I blew out an older G4 Clifford once by being lazy. Also NEVER parallel out to the two starter wires, always adjust your outputs as above or relay it.

time is not a concern for me. I have a unique experience, because I am firefighter/medic and work at a restoration shop on time off. kinda boutique work. the job takes whatever it takes. i get to solder evrything and heatshrink. BUT it's mostly pre computer stuff. I have been getting more late-model stuff after a couple installs made it around to some shows. so i have to try and catch up with everybody. thanks for the help evrybodyThe RIGHT way is the ONLY way.