Where does the logicon power wire originate from?
 

On the 13 pin plug on the back of the logicon, there is a light green w/black stripe (LG/B) wire. The FSM trouble "heater" shooting section says to check for 12V at this wire and that it feeds everything from the logicon to the blower and the mode selector motors. Right now, no part of my heater system works and I'm using a logicon that Icemark reworked for me. I test the wire and I get 0V, so it has to be unplugged. I doubt its broken cause its not blowing the fuse. When I plugged it back in and using a jumper wire, applied 12V to it right at the plug to the logicon, everything started working. I had A/C but I removed it, I've swapped out the auto tranny for a manual one, and I removed the engine harness and I'm using a Haltech. I must have removed or unplugged its power source at some point in time.

So where does this wire start from? I can't find the other end of the harness, and none of the schematics or diagrams that I looked at show where it comes from.

I'm not for flip on logicon, but I see two sources. One is from the Illumination fuse and the other the CIGAR fuse. Anybody can feel free to correct me. Have at it.

What part of the thing isn't working? Or shall we make a shorter list and list the things that work?

Nothing works. The logicon lights up when I turn the dash lights on, thats it. But if I give the LG/B wire power, everything works as advertised. I can't just hook it up to any power source, or it starts making crazy noises like the air-recirculate door motor is trying to drive beyond the full open or full close position. If I give it power from a source that has power when the key is in the run position, it doesn't make any strange noises. I got enough of it figured out that I'll be able to wire it in to the proper power source so it will work.

Logicons always puzzled me. It seems anytime I turn the key to ON, I hear some motor going open/shut. Happens every time. Not interested enough to find out why since everything works on the logicon.

On the wiring diagram, the power wires SEEM to me to be the Blue/Black from the Acc and the White/Green from the Batt. I'd pull the plug and turn the key ON and see if those two wires have 12vdc or not. They go to the two fuses I mentioned earlier.

Frankly I remember that skinney ass light green/black wire from my past. My heater motor wouldn't work right and I jumpered 12v to it so the motor would run faster, if I remember right. The light green black that is located somewhere around the heater motor area. In the long run after a couple of years, my problem was fixed by replacing the box the fan is bolted in. It had some kind of resistor mounted on the structure out of sight. Mine was kaput.

I see the other power wires you are talking about I think one is for the lights in the logicon. I used the trouble shooting part of the "Body Electrical" section of the FSM. On page 99 the top of the first chart is for "Nothing works". First step is check fuses, which were good. Next it has me unplug the connectors and check the light green/black wire on plug G01 (the 13 pin connector) for 12V. I got nothing, and it says to fix that, repair the harness; light green/black wire to battery.

If I supply it with battery power, the heater and everything works, but it works even when I take the key out. Normally it should only work with the key in the run position. I tried a couple different places to get power and depending where I plugged it in, it started making wierd noises, but I found a good source for it that lets it work properly.

My friend's S5 turbo swap that I'm working is doing the same thing (no power to logicon at all but illuminates). Is there anything I can do to help find the solution, I'd like to fix it myself as well.

Did it work before the swap? If it worked then and it doesn't work now, read what I put in the post just above yours about checking the light green w/black stripe wire and see if that will help. Its section 15, the part for Body Electrical, page 99 has troubleshooting for the heater system.

I'm not sure if it worked or not before. The car was an uncompleted project car that I finished up. I'll do the tests you described above if I have a chance today.

yeah, the reason you can't just use anywire, is because they also get back fed power from the blower unit and blower amp.

It has to be switched power just like the blower.

In the online 88 manual they show a blower motor plug. It has eight pins/sockets. One is Black/Yellow. That should be 12v with the key ON. See page 50-67 of the online manual for 88models.

I see what you are talking about. Its the only one coming from ignition postion 1. I used the chart on 15-99 (also the online version of the FSM) and it lead me to the LG/B wire. I already ran a new wire and soldered it in and everything. I'll check that B/Y one tomorrow just to see if it has power, but I'm not going to fix it if it doesn't cause I got everthing working now. On the top of page 50-67 it says "Except Non-turbo MT" not sure if that matters but my car is a '86 GXL and it original had an auto tranny in it.