So how do you guys go about soldering those big wire i believe their 12AWG wire for the remote start ribbons to the ignition harness? I try to solder it but it never get hot enough to push the solder through. Or do you guys use some kind of connectors?

 

i use a weller soldering iron with a FAT 1/4 inch tip. thing gets hot enough that i was able to solder some 8 gauge wire together. tiny tiny soldering irons aren't able to transmit heat effectively enough imo for the big things

 

Walmart soldering irons don't get hot enough. You need one with power, like a weller.
Or you can always torch solder it (if you're careful enough).

 

get a soldering gun... I have a 100w/140w weller that gets hot