SMOKNISB

My 4WD light wont come on when put in 4WD. It wont even come on when you first turn on the key like the rest of the lights. I'm not sure that it is even engaging the 4WD correctly, but I figure I would start with getting the light working.

My question is, How hard are they to change? Is it a fairly simple job.

phox_mulder

Make sure the 4x4 is engaging first.

Throw it into 4x4 and try turning a sharp corner, you'll know right away if it's working or not.
(slow speed of course)

Once you've verified, then you can think about tackling the light,
I'm guessing the light is harder to fix than the 4x4 not engaging.


phox

SMOKNISB

After doing some more searching, looks like the light is actually a soldered on LED. Which is no big deal, as long as I can find one. Should the 4WD light come on during the bulb test when the key is first turned on? I also read about some cluster test by holding down the trip reset, then turning on the key. Is this true?

I'll try tomarrow and see if it is actually engaging or not. Thanks for the reply.

phox_mulder

I don't think it comes on when the rest of them self test.

If it's an LED, it isn't very likely to burn out.


phox

SMOKNISB

OK..well it may not be engaging. Anyone have any tips to solve an engagement problem?

phox_mulder

99% of the time, it's a vacuum problem at the CAD.
Front axle, passenger side, check the rubber hoses connected to the box.

If they're both good, check for free movement of the lever inside the box.


phox

SMOKNISB

What does CAD stand for? I think I know what you are talking about though after looking for more info. Is that the vacuum activated lever that actually engages the front axle? I'll check it tomarrow. I think the switch that activates the light is actually mounted to this device also.

jrs_dodge_diesel

CAD=Central Axle Disconnect. Instead of using locking hubs or a live axle (axle that is always engaged) our Rams have CAD.

SMOKNISB

Well the 4WD light is not bad. I tested it tonight by jumping the harness plug together, and the light came on. But I tested the switch and it is bad. I might work intermitently, buy it had 300-500 ohms across it when closed. Sometimes more, sometimes less. So i'm going to replace it. I didn't have a chance to actually engage the 4WD and turn and see if I could tell if it is actually engaging. I dont think it is.

One more question. If I do need to pull the CAD off, will diff fluid come out? If so, how much?

SMOKNISB

Well I checked some more stuff tonight. I checked the vacuum on the CAD unit. I have 25" of vacuum on each line. One line in 2WD and the other in 4WD. so that is working good. I jacked the passenger side up and engaged the 4WD and I could still spin the tire, so I know it is not engaging. I am going to pull the CAD unit off. Will I lose any diff fluid when I pull it off?

I have also read about some people replacing the factory CAD unit with a cable operated posi-lock, but I can not find where they purchased them. Anyone know?