I'm guessing he looped it. Thats what I'm going to try.

Chris R my light stays on. My switch is good. What could it be?

Only one vacuum line should have vacuum at a time. The vacuum pulls the diaphragm in opposite directions sliding the collar on the axle to engage / disengage the 4WD

Is the red line the one should have vacum to engage the 4x4? ​@@WilliamFrawley

Try cleaning the contacts on the switch & plug first and see if that helps. Then use a jumper wire across the plug (like in the first part of the video). The 4WD light should come on and stay on, doesn't matter if you have it in 4WD. If you drive it like this it should stay on constant. You can try this to make sure there isn't anything wrong from the plug back to the dash light. If all of that checks out then possibly the diaphragm on the 4WD actuator is leaking or going bad. When you shift into 4 wheel drive, there is a shaft in the actuator that moves the yoke and the end of this shaft presses the switch to indicate that it is in 4 wheel drive. But the actuator can shift partially into 4 wheel drive and feel like it's in 4 wheel drive but not be shifted far enough to actuate the switch completely. If it is not completely engaged, this puts a lot of stress on the "collar" and end of the axle splines. I have another video showing how to replace the actuator if you want to see how it works.

@@WilliamFrawley thank you for your feedback.

When you shift into 4WD, a rod inside the actuator pushes against the switch. If it doesn't shift out of 4WD the light will stay on. You can try taking the switch out of the actuator and push against the rod inside with a punch or something to manually shift it out of 4WD. You may have to have the front passenger tire off of the ground and rotate it slightly back and forth while you push the rod in to disengage it. Also, just to make sure the switch is working, take it out of the actuator, plug the wire back in and then push the button in and out on the switch and have someone watch the dash light to see if it goes on and off. (I have another video that explains how to replace the vacuum diaphragm if that is the issue, it also explains how the system works)

Jay Gould so I disconnected the switch. Light went off. When I put it back on the light came back on. I took the actuator out and seems to be working fine. I manually moved the gear once I removed the actuator and there was a little resistance when sliding, is That normal? Also before all this when I would put it in 4h the light went out but when I put in 2H the light comes on. i also just changed the transfer case vacuum switch hoping that it fixed the problem but no. Which now lead me to remove the actuator

I will try having my friend look at the light while I push the switch button manually. Great idea. I was just messing with the truck earlier wish I would’ve seen this earlier

On the front axle 4 Wheel Drive Actuator

Yes, a Prusa MK2/S. Very useful for prototypes