I posted this info on another site about a week ago, but since I've also used this site for information, I thought I'd share my findings here too. I may have scared people off on the other site because my post was too "wordy" but oh well. I did my part to share info at least. I'll keep it short here though.
I originally wanted to make a pcb version of a roof controller, but it was too expensive to print a one-off board. So once I understood what I needed to do, I decided to use some common auto relays. This makes it much simpler for guys who are not too tech savvy to put together a pcb, but can at least tie some wires together. And I only cared about two things anyway: The one touch function and opening/closing the top at speed. This allows that.
For the one touch you will need…
2. SPDT 12V Relays (The ones with 5 blades instead of 4) Make sure they have 87 & 87a. RL45’s at Auto Zone (The blazer brand ones at autozone have two 87 ports and are useless)
1. Pack of wire splices (The blue ones that let you connect a wire into another without cutting it). Get the smallest gauge pack you can find. The 16-18 or something like that.
1. Pack of female .250” blade terminals. Again, find the smallest gauge pack.
1. Roll of 14g or even 16 gauge wire. I used 12g for mine which proved useless and took up more space. The original wires are so thin anyway. And only supply a signal, not the actual power for the top.
Then supplies…electrical tape, pliers to crimp the terminals and splices, and if you wanna get fancy, heat shrink tubing, soldering iron, an inline fuse, and some patience.
All in all, the bare minimal should cost you around $30 (depending on your area and extra stuff if you hoard stuff like me).
How it works… NOTE: THE WIRE COLORS ARE FOR ILLUSTRATIVE PURPOSES ONLY. YOU CAN MAKE THEM ALL BLACK IF YOU PLEASE. Looking at the diagram, you see that flipping the switch in either direction will provide ground to either the blue or green circuits, so only one relay will be activated at one time. This triggers the relay to allow power to flow from 30 to 87 on the active relay. The bridge from 87 to 85 allows the relay to remain powered even after you release the switch because the green/red wire that is associated with the switch lamp provides ground until the light goes out. However, this relies on the fact that this ground signal will always require the opposite relay to be inactive thus allowing a flow from 30 to 87a. When you flip the switch in the opposite direction during operation, both relays are active, thus removing the 30 to 87a flow needed to power either relay. This allows you to flick the switch to stop the top and even close it if you change your mind. Nifty. One thing to note…because the original harness is so thin, the wire splices just pinch the wire and don’t always make a strong connection. I had to manually open each one and pull the wire sheathing apart to expose a bit of wire so the teeth of the splicer can make good contact. I hope that made sense. Just use a multimeter if you’ve got one to make sure the connection is established correctly. Leave some long leads coming off of the relays so that you can make the connections on the right side (this is all done under the gear selector trim that holds the window switches) but run the wires behind the shifter and into the left side where you can tuck in the relays out of the way. I hope that made sense.
ON TO THE SPEED LIMITER!
I knew that 74 and 56 supplied speed information to the module. I just didn’t know how. I took a leap of faith knowing cutting both wires. I tried connecting them directly to ground. Nothing. Directly to power. Nothing. Then with my multimeter on “beep mode”
… I realized that the 56 coming from the car harness was “pulsing” with the car parked. Wire 74 was not. Just solid ground. SO…… I knew a resister would change the voltage and I didn’t want to wait for one from ebay, so I took apart an old radio and cut one out. I found was one that measured 620. I then left the 74 lead unconnected to anything and put the resister inline from incoming 56 to the 56&74 that go to the control unit. Took it out for a drive and damn-it, it worked! It works up to about 45mph. Any more and the switch won't activate the top. So yeah, the 74 should be the 5th wire from the right at the back passenger side corner. It’s Green/White. 56 is on the next row over and two pins forward. Blue/Green. Be careful, there is an identical wire further ahead at another pin so follow the correct wire on the loom carefully. But these are the same two wires you’d end up cutting for a module anyway.