Freaking Rear Locker Stuck

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Matador98

Matador98

SILVER Star
Joined
Aug 11, 2004
Threads
19
Messages
475
Location
Santa Maria, CA
Website
www.esaero.com
Ok, before we start, I've searched, read the other threads, and have the FSM.

The rear locker on my wife's 100 we bought in March is stuck, and I knew it when I bought it. The CDL does work, but the light in the dash doesn't light up. In prep for surf n' turf, since my wife would be driving, I figured I'd take a look and see if it's siezed, etc. I also bought a light to replace the CDL indicator.

I started by trying to get it to engage the Rear some more jacked up in the garage with no luck, and before I tore into it to see if it is siezed, I replaced the CDL light instead. After replacement, it still does not work. The CDL however, mechnically does work, but i also found out it only works with the button pushed. If I put the truck in 4L and don't push in the CDL button, the CDL does not work, and I thought it was supposed to automatically in 4L. So maybe it is an indicator.

There are three indicators on the transfer that I'm aware of from the FSM, one being the L Position Switch on the front side of the transfer, and then the two Transfer Indicator Switches, one being (Center Diff. Lock) and the other being (Low Switch).

I think the problem is with one or more of the indicators, since the light does not go on in the dash, the ECU doesn't know the CDL is engaged, which is probalby why the Rear Locker won't engage. It doesn't know the CDL is engaged AND it also doesn't know the truck is in 4L because the CDL doesn't go on automatically. So, does one of those indicators control both of those and give signals to the ECU giving the OK for the rear to engage?

Also, where the hell are the Center Diff ECU and the Rear Diff. Lock Control ECU. It is really hard to tell from the FSM and I didn't feel like ripping the dash apart until I consulted the MUD knowledgebase.

So, a lot of the other similar threads to this reference a stuck actuator, etc., but never post up what the actual problem and/or results were. Anybody from those thread here?

What do you guys think, maybe somebody has crossed this before. Sorry for the long post.
 
Yes, I would start with removing and testing those switches on the transfer case. Sometimes you just need to work it a bit.
 
How exactly would I go about testing them. I don't see specificaitons for it in the FSM, other than testing the ECU's, which I still have no clue where they are. Does anybody know the spec on them? I guess I could just pull them and measure how the resistance changes as they are activated, etc., and if one doesn't change, it's bad.
 
IIRC, it's just a metal ball at one end and two wires that come out of the other end. You just check for continuity while depressing the ball. I think you can even check it on the vehicle, just put it in LO and check for continuity.
 
114 views and hoser is the only one with any idea or experience? I know somebody else had delt with similar problems, give me some insight!
 
Never seen a ECU go bad, but have seen the switches go bad. Remove them from the transfercase, depress the ball and check the contacts to see if they are switching. Sometimes they will work after some cleaning with electrical cleaner. Sometimes the connectors are caked with mud and corroded. Clean the connectors as well. I would start there before I would try and trouble shoot an ECU.
 
it is much easier to check everything when the vehicle is on its side as Christo shows in his avatar :grinpimp:


On my 80 series, I ended up having to take the switches and blast them with electrical cleaner as Christo mentioned.

take the switch out and use a multimeter to check the operation - it sounds like you have a good idea about the workings of the system and when one piece doesn't work, the rest of the system won't start.

you might want to make a call and just get a new switch if you want to be done with it in a day and not have to dilly-dally with it anymore...


bk
 
Are the connectors like hoser said, just have to check of continuity or lack there of when the ball is pressed/not pressed? Or does the resistance change when depressed, but there is always continuity?

Thanks for the help, guys. Are all the switches the same part number, so I can buy one and replace any of the three if bad?
 
Hi,

I purchased my 99 with 84 k miles on it, and the rear locker would not engage. I had it at the dealer for other PM and asked them to take a look. They corrected the problem by applying power directly at the locker, bypassing the switch. It works fine now.
 
Matador98 said:
Are the connectors like hoser said, just have to check of continuity or lack there of when the ball is pressed/not pressed? Or does the resistance change when depressed, but there is always continuity?

Thanks for the help, guys. Are all the switches the same part number, so I can buy one and replace any of the three if bad?
Click to expand...

They are normally open switches that close when pressed (Not sure if all of them are like that). Also not sure if they are all the same part number. The ball side is normally the same, but the connector side is not.

Call the dealer and ask them to fax you a exploded diagram with part numbers.
 
Abe Nitro said:
Hi,

I purchased my 99 with 84 k miles on it, and the rear locker would not engage. I had it at the dealer for other PM and asked them to take a look. They corrected the problem by applying power directly at the locker, bypassing the switch. It works fine now.
Click to expand...

So essentially, your rear locker is hardwired to the switch in the dash, completely bypassing all the electronics? That's not a bad idea, but I'll pull the sensors and clean them first.
 
Matador, I remember reading this on Slee's site when I was trouble shooting the CDL on my 80... transfer case is very similar to 100. Exactly the same method for testing the switches. If you need more info, search the 80 section. I believe the locker set-up is very similar and there are many more 80's with rear lockers than 100's.

http://sleeoffroad.com/technical/tz_centerdiff.htm
 
Hi Matador98,

You are on the right track, as others have said the switches on the transfer are the most likely cause. I'll throw a bit more in here to help confuse you.

I am assuming that when you push the CDL switch, your hear the CDL motor operate and lock the centre diff. The motor stops once locked. You push the switch again and you hear the CDL motor operate and unlock the centre diff and the motor stops. If this is correct, the CDL switch and motor and motor position detection switch is working correctly. (The motor position detection switch is with the motor which controls the motor so it does not burn out)

The CDL light on your dash is activated by a seperate detection switch on the transfer case. It will have 2 wires going to it, most likely a Pink/Black stripe and a White/Black stripe. Power is provided to your dash light from the 15A GAUGE fuse and then runs down to this detection switch via the Pink/BS. The switch closes when activated and switches to ground via the White/BS and allows current flow through the CDL lamp.

To test this circuit, unplug the detection switch on the transfer case and check for 12 volts on the Pink/BS. Using an Ohm meter also ensure the White/BS is connected to ground.
If there is 12 volts on the Pink/BS, then shorting it to ground should light up your dash light. If you don't have 12 volts there, then further investigation is required as to why not. (The 15A Gauge fuse also supplies power to the LOW RANGE Detection switch, which controls the selection of the REAR LOCKER)
If the lamp lights up then the Detection switch may be faulty. To test this switch put an ohmmeter across the terminals of the switch and operate the CDL and the switch should close and make contact.

There may also have been a mod done to your vehicle that allows the CDL to be operated in high or low, a lot here have done this mod, (the 7 pin mod), one I recall said his came like this from the factory.
However, some have pulled a connector off one of the transfer case switches that allows the CDL to be locked in High or Low. If this has been done to your vehicle then this will stop your rear locker from working. I would definitely fix the CDL lamp circuit before starting on the rear locker problems.

The three detection switches on the transfer should be as follows
CDL detection switch - Pink/Black stripe & White/Black stripe
Transfer case Neutral detection switch - Yellow/Green stripe & White/Black stripe
Low Range detection switch - Red/Blue stripe & Black/Blue stripe

The REAR LOCKER is controlled via the LOW RANGE detection switch. This is fed power from the 15A Gauge fuse as mentioned above. If the LR detection switch does not switch and supply power to the difflock ECU, the rear locker will not activate.
To test it check there is power on the Red/Blue stripe wire and that the switch closes when low range is activated (same test as switch above)
If you have power there and the switch is working and power is going away on the Black/blue stripe wire, then that is a start as this should go to th difflock ECU.
The difflock ECU also requires power from the 20A DIFF fuse.
I will leave it there and if you get it working to this point and the rear diff still does not work I will write up a couple more checks and tests for you before you pull it down. Hope this helps.
EDIT: CDL switch is PINK/Balck stripe
 
Last edited:
Awesome guys. Now that I know what to sniff for, I should find it. Thanks for the help! Hopefully this thread will be a good resource for others as the 100s age. Actually, maybe I'll document this and write up an article....
 
My locker operates through the stock switch. The locker would not activate. Applying power directly to the unit at the axle unfroze it, and since then it has worked perfectly.
 
I have what I think is the exact problem on my '99. I'm pretty sure that my CDL activates when i press the button, but i cant hear it when i shift to low. My RDL does not work (but it did as of about a year ago).

How do I go about accessing the electroncs in the transfer case to test connections? Is there a panel that pops off somewhere?
 
DavidsonCruiser said:
Ah ok so I need to go under the car. I was picturing finding switches inside the car.
Click to expand...

The CDL lock detection switch is on top of the front extension housing of the transfer case, yes you can get to it.

The Neutral detection switch and the Low Range detection switches are located next to each other on the rear extension housing of the transfer case. You can get to the connectors to easily unplug them and test them but they will be a bit harder to get at.
The Neutral detection switck comes in from the top of the extension housing and the Low Range detection switch comes in from the side of the extension housing.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom