Quick question: Does anyone know exactly how the CDL detection switch work? I am assuming that when the CDL is locked, it creates a circuit between the two wires. Does the spring push the end of the switch down and that's what grounds it? Or is it opposite, that when the CDL is engaged, it pushes that round part up and then grounds the two leads? Any idea?

 

I take it you still haven't tried turning in a tight partial circle to see if the CDL is locked, if not do it before you waste time wondering if it is working.

 

Hey mike I did try it yesterday. I manually switched the CDL on. I couldn't tell if it was engaging or not. It sort of felt like the front was binding up but I just wasn't sure. I was thinking about removing the front propshaft, engaging the CDL, and then seeing if it is actually locking or not.

Has anyone had a t case fail where just CDL stops working? Everything else works fine. Hi-lo etc.

 

If the front end was binding up, then your CDL is engaging, so now either you have a bad switch or a burned out cluster light.

 

If you drive around and your CDL light comes on, it's engaged.

 

Bballjames did you fit the new switch? Did you find the final cause or fault?

 

If you put an ohmeter on the two terminals of the switch, you should read nothing when the button is released, and continuity when it's pushed in. In other words, there is contact when the button is pushed in. Buy a good quality switch, I bought one from China and it did not even make it to the transfer case, it broke while I was installing it. Also the switch has to be screwed in almost all the way for it to work.

The CDL is all mechanical inside, turning the spigot pushes a dog shifter that mates the two sides of the differential inside the transfer case, it's pretty basic in there. There is a spring on the mechanism that will engage the lock only when the two halves of the differential are aligned. So turning the spigot will not necessarily engage the lock right away. If for example there was a foreign object that prevented the dog shifter from moving, the lever would still go all the way and compress the spring, but the CDL would not engage, but that's not very likely.

 

Installed a new switch that I bought from Atlantic British and it works great! Easy install (minus ripping your console apart). Don't forget to put the spacer nut on the new switch before you put it in!

 

To answer or further elaborate on a question asked in this thread, the mechanism the locks the CDLin a Disco is mechanical only. Unlike some rovers there is no electronic motor or solenoid that acts on your command to lock and unlock. Some rovers do have these though. I found this out while getting oriented to my p38 Range Rover and thought that the transfer case was broken because I switching the gear selector over to low side and then pulling it into drive before the electronic motor/solenoid could finish it's job of switching the transfercase to low side. I was driving around with the gear selector in low side but obviously still in high side. I had to learn to be patient and give it the time it needs to work it's magic... or leave it in low side since I only use it for offroad play. Never sees pavement.