CDL Will Not Engage....

[jcwhitty]

I'm back! After looking back through the thread, I feel a bit embarrassed. What is 10 "gauge" Duh. Somehow my mind went to 10 gauge wire, and stayed on that track. Anyway, I still have not cured my problem, but since I still could not get that relay to energize when installed in the truck, I kept testing. I have attached what I found. (See pages 1 and 3. Must have had the scanner set on duplex) Hoping for some additional suggestions.

Thanks again, John.

 

[bloc]

You won't get a neutral light on the dash unless the transfer is in neutral AND the transmission is in Park. It is intended to let you know that the truck won't stay still despite being in Park.

 

[jcwhitty]

Thanks, and I do have the neutral light.

 

[george_tlc]

Ok, I think the manual doesn't show the correct wiring to the CDL control relay. As shown it would never work with a CDL switch, but since the diagram is set up to show how the vehicle is supplied OEM it's fine.

Below is what I think is a more accurate diagram of the relay, NOTE the pin 6 connection to the CDL switch. Now this diagram makes sense

This is taken from the 100 forum, but makes a lot more sense since 'something' has to power the right bottom relay, and certainly nothing in the '96 FSM could do that once pin 7 is removed...

It also explains the 'mystery' pin 6, it connects to the CDL switch. Without the switch it just hangs free and does nothing, with the switch it becomes the +12V source for the bottom right relay and then everything makes sense.

So, the CDL switch provides power EITHER to Pin 9 or to Pin 6 depending on whether you are unlocking or locking the CDL.

cheers,
george.

 

[jcwhitty]

The difference between 94 and 97 is as follows.

97 only has one wire running from the dash switch to the CDL relay, it is Black, on pin 9. There is a jumper in place of the dash switch that gives this +12v through the 10A "gauge" fuse any time the ignition is on. It appears this makes it so that the transfer lever being in Low is the only thing that engages the CDL, as stock on a 97.
94 has two wires from the dash switch, one black on pin 9 that serves the same function as on a 97, and a Black/Red wire on pin 6. There is a note for a jumper between Black wire pin 9 and +12v as in the 97 labeled "W/ABS". The black/red wire is labeled as "W/O ABS" on the 94 EWD. Also, w/o ABS gets the CDL dash switch, it appears.

So it seems the 94 chassis, even if it came with ABS, is wired with the 'W/O ABS' wiring for the CDL.

Do you have the schematic for the 94 cruiser? Or for that matter, does anyone? Much appreciated, John.

 

[bloc]

Here you go

 

[jcwhitty]

Thanks......

 

[george_tlc]

...and the 94 schematic shows that pin 6 exists (which it must) even on the 96/97 models (even though not shown in their EWD).

So, Either Pin 9 OR Pin 6 gets +12V (with the CDL switch installed and Pin 7 is disconnected so that the top left relay NEVER gets energised since its coil will NEVER get 12V). So, only the bottom 2 relays do all the work.

So, that means you will ONLY hear the relays click if:

a) +12V gets to either Pin 9 or Pin 6

AND

b) the CDL motor/switch correctly provides ground to either the left relay coil or right relay coil.

That means, measure power right at the relay and there should be +12V either at 9 (CDL switch off) or 6 (CDL switch on). The left relay will click to turn the CDL off (and once off it will be de-energised by the limit switch in the CDL actuator). The right relay will click to turn the CDL on (and once on it will be de-energised by the limit switch in the CDL actuator).

IF you NEVER get a click sound but there IS +12V at Pin 9 or Pin 6 then it means you have no ground path coming from the limit switch in the actuator. That limit switch is broken/stuck or its ground (pin 4 of the actuator plug, per Bloc's 94 diagram) is not present.

Since you stated you had measured +12V at Pin 9 and Pin 6 as you cycled the CDL switch on/off I'd suggest you look for the missing/bad ground.

With the updated CDL diagram of the '94 (same info as the 100 series) I know FULLY understand how the CDL relay module and actuator interact and work. We'll get to the bottom of your problem with some more measurements.

I'll be off internet access most of tomorrow... but back in the evening.

cheers,
george.

 

[jcwhitty]

Hi George.....

Thanks again for getting back, and taking a look at the schematic.

I have already determined that there exists a ground on terminal 4 at the CDL control motor, in addition to terminals 2 & 3, so I fear it is in the control motor itself. I did find on the very last page of the FSM where I can test the CDL control relay, so I will go through those steps, just in case. Otherwise, can I try to directly run the control motor forward and backward by applying positive 12 volts to terminal 4 on the CDL Control Relay Connector, and negative to terminal 1, and vice versa if the control motor is polarity sensitive? I was hoping that maybe just cycling the motor a few times might help.

John.

 

[george_tlc]

Yes, +12V and GND one way will make the motor turn in one direction, flip the polarity to turn the other way.

The PROBLEM though is that without the relay control logic, there is nothing to prevent the motor from going too far when you manually apply power and I don't know if that would do something 'bad' to the actuator mechanism...

The combination of the CDL control relay AND the limit switch in the motor assures that the motor power will be disconnected when it reaches either end.

Actually you should have GND at EITHER pin 5 or pin 6 of the Motor assembly (not both at the same time). Pin 5/6 are the limit switch toggling 'output' with pin 4 as the permanent ground 'input'.

If your CDL is presently disengaged, then the should be ground at Pin 5 (if I have my engaged/disengaged order correct in my mind, if I'm wrong then Pin 6 would be GND).

cheers,
george.

 

[Tapage]

I takes about 2 segs to engage .. keep that in mind if you decide to run manually ..

 

[jcwhitty]

Well, it is looking more and more like it is internal of the CDL motor. When I check the Center Diff Lock Terminal Connector (C4), there is only continuity to ground on the number 2 terminal, and I believe that there should also be on 5 or 10. The CDL relay checked out and I have ground to number 4 terminal at the CDL Control motor (C1).

I chose not to try engaging the motor manually as mentioned above for fear I might lock the center diff. Can you confirm which terminals I should energize to retract the motor, and I might consider giving it a short jolt. Otherwise, are there any other suggestions for what I might try before removing the motor though I am not sure when I will have the opportunity. I will need to depend on the "full time in the mean time", which is only half bad.

Thanks again for all the input.

John.

 

[george_tlc]

No, you will ONLY have GND on the control relay Pin 5 and 10 (Relay pinout) when the limit switch is at one end or the other. The fact you have no continuity on either means the limit switch isn't at either end or the switch is dead. Obviously the connector needs to be connected to measure the GND path (through the CDL motor/limit switch assy)

To try to 'disengaged' the motor you would apply +12V to Pin 2 of the CDL MOTOR ASSY and GND to Pin 3 (I think that's correct...)

With the CDL disengaged the limit switch should be in the top position (on bloc's diagram), so GND from Pin 4 to Pin 5 (CDL MOTOR ASSY pinout), i.e. Pin 5 should have continuity to GND at that point.

If you have no continuity to GND from either Pin 5 or Pin 6 (of the CDL MOTOR ASSY pinout) then there's definitely something wrong inside that assembly and you'll need to pull it and open up to see what's up with the limit switch mechanism.

cheers,
george.

 

[jcwhitty]

Thanks George....everything you describe is correct, and I need to remove the switch. I read where "tools R Us" did not recommend running the motor with an outside source, as I was considering, so I will respect his opinion.

As for removing the motor, it looks like the job can be a real bear. Might even be easier to just drop the transfer case, and work on it out of the vehicle. Once the part is out, hopefully it is repairable....I understand they might be difficult to source at this point in time.

Thanks again for your help.

John.

 

[jcwhitty]

Well, it has been a while since attempting to trouble shoot the CDL, but I have good news. (I think). I did some off road travelling not long ago during a fishing trip in Northern California, and just decided to start flipping the CDL lock on and off, putting the transfer case in low range, etc. Just trying to exercise things. After maybe 20 times, the CDL lock light came on, and the CDL had engaged! Boy, was I a happy camper! In the future, whenever I drive the vehicle, I am going to make a point of engaging and disengaging the CDL on a regular basis, along with the front and rear diff locks, which hopefully will keep things moving, you might say. Regardless, I learned a lot and am appreciative of all the support from the forum.

John.

 

[Bloomer]

Almost too much info here to understand what to do next. What I’ve got is a 95 year model, 4 low and FR/RR diffs worked fine since purchasing in October. Installed a new OE CDL dash switch last week, all worked fine. Cycled transfer case to 4 Low today (just to work it on a dirt road, which I’ve been doing routinely) and no ABS/CDL lights and doesn’t particularly “feel” like it’s in 4 Low. Not hearing any clicking and pushing the CDL button does not cause any whirling sound. The transfer case lever also felt a little easier to operate than usual.

I’ve checked:
30 A fuse - good
Linkage - appears good
Jumped the switch connector on the transfer case using paper clip - ABS/CDL light comes on.

Any thoughts on what to check next? I’m not convinced that successfully jumping the switch, in this case, means the switch is the problem as it’s not clear to me if there’s another issue before the switch thats potentially not getting power to it to trigger the switch on the transfer case. Although, I’ll admit I don’t know enough to feel confident I have done enough to make that call.

Any help is appreciated.

 

[Bloomer]

Almost too much info here to understand what to do next. What I’ve got is a 95 year model, 4 low and FR/RR diffs worked fine since purchasing in October. Installed a new OE CDL dash switch last week, all worked fine. Cycled transfer case to 4 Low today (just to work it on a dirt road, which I’ve been doing routinely) and no ABS/CDL lights and doesn’t particularly “feel” like it’s in 4 Low. Not hearing any clicking and pushing the CDL button does not cause any whirling sound. The transfer case lever also felt a little easier to operate than usual.

I’ve checked:
30 A fuse - good
Linkage - appears good
Jumped the switch connector on the transfer case using paper clip - ABS/CDL light comes on.

Any thoughts on what to check next? I’m not convinced that successfully jumping the switch, in this case, means the switch is the problem as it’s not clear to me if there’s another issue before the switch thats potentially not getting power to it to trigger the switch on the transfer case. Although, I’ll admit I don’t know enough to feel confident I have done enough to make that call.

Any help is appreciated.

As strange as it may sound, I used a wrench and lightly tapped on the CDL actuator and CDL switch transmitter and everything is working.

 

[LINUS]

As strange as it may sound, I used a wrench and lightly tapped on the CDL actuator and CDL switch transmitter and everything is working.

You never used the ‘bigger hammer’ mentality before?

To me that’s the strangest part of your post!

All old things generally need a ‘tap’ on occasion.......

 

[rolliges]

Probably dried grease in the CDL actuator.

@Bloomer
Did it disengage afterward? Does it now go into and out of "lock" when you go into 4-Low??

 

[ppc]

That's called percussion maintenance.