overdrive not working - fourth gear switch?

[dahicori]

Hello ,

So yesterday my overdrive stopped working. Relay is ok, I have good values on the button of the shifter. Good oil level. So I started cheking the wiring. I pulled the wires from the shifter and without giving it any force two wires came right off, completly rotten. I red somewhere that fourth gear switch have a single pin, so I dont know what I picked up but I guess the fourth gear switch is not receiving any electricity att all . Access from underneath the car is very limited. Can you tell me if it s feasible to change the wires? I saw many guys on youtube giving tips to bypass the solenoid, the relay etc

But for some reason I'd rather changer the wiring.

thanks!