Cruise Control Help Needed

[moparguy]

Help, evidently I need adult help in fixing my '95's cruise control. I bought the truck new and about 5 years ago the cruise went out. Now I've fixed this problem on a few 12 valve trucks over the years and it's usually easy, just not on my truck for me at least.

When it first went out I checked the usual suspects, vacuum lines, good. Changed brakelight switch, no help. Picked up a cruse control switch for the steering wheel at a salvage yard, swapped out, no help. Disassembled the original cc switch, cleaned reinstalled, no help. Looked for broke wires, nope. Got tired quit.

Fast forward to 2019, I've been talked out of retirement to help a pipeline company in Midland Tx build and update it's project books so I decided to drive the '95 since the wife feels her '15, 2500 Ram should stay hooked to her horse trailer. Driving 700 miles with no cruise plays 'ell with my right leg and foot so I've re-tackled the cruse issue.

I did revisit all the steps mentioned above, vacuum lines still good with 24" of vacuum at the cruise control vacuum module under the battery. Pulling up on the brake pedal makes no difference. Everything else works and no noise from the vicinity of the clockspring. Fuse is good, changed out for good measure, no help.

Based on a Youtube vid I did discover a bad coil in the vacuum servo under the battery and found a new replacement for about $50 delivered that is just the module, it's for a 95 Jeep Cherokee and is a exact match. No cable the pump but the servo and electrical plug pins are perfect. NO CRUISE after making the change.

So, at this point I'm thinking in my repair attempts I've likely created a problem, perhaps with the cc switch on the steering wheel. I bought a new replacement off Amazon for about $90 delivered that's actually for a 96 and up truck. It has the lighted second switch from the left and one less wire than the original switch. While not an exact replacement the switch purchased is represented as a '95 replacement by several vendors and one poster I found.

Does anyone know for a fact if the switch described is the likely problem? The difference is the on/off functions are both in the first button rather than "on" in the first button, and "off" in the second button in the original '95 switch.

At the moment I'm thinking, computer (big deal replacing these days).

Clockspring (no other indicators this is the issue)

Broke wire under the steering column.

That's all I got. Thanks for any and all help.

RonR

 

[DavidC]

From diesel truck resource
A BROKEN WIRE IT WAS!
I found a broken wire just under the plastic cover under the steering wheel.
It was easy to find.....right there in plain view.
I soldered it up and 3M electrical taped it.
Cruise works great!
Thanks for the heads up!!
https://www.dieseltruckresource.com...cruise-control-dont-work-how-diagnose-276911/

 

[dieselshadow]

Is the alternator working? Is it going into overdrive? Tachometer working?

The crank position sensor allows all of this to function and was a common failure early on.

 

[moparguy]

Yep, everything else works. Standard transmission though. Forget the name of the item but I unplugged and repluged the connector that's attached to the head under the radiator hose as suggested somewhere. No help.

 

[dieselshadow]

I would also inspect the actuator under the battery a bit closer. They usually failed after so many years because the battery would seep chemicals on it. Even cleaning the engine would lead to crap landing on it and eventually rotting it away.

I don’t remember the actual failure, only that they would.

 

[DavidC]

I would also inspect the actuator under the battery a bit closer. They usually failed after so many years because the battery would seep chemicals on it. Even cleaning the engine would lead to crap landing on it and eventually rotting it away.

I don’t remember the actual failure, only that they would.

Can that be tested with a handheld vacuum tester ?

 

[BigPapa]

I’m going to say you need the correct switch.

 

[PBJ2500CTD]

Yep, everything else works. Standard transmission though. Forget the name of the item but I unplugged and repluged the connector that's attached to the head under the radiator hose as suggested somewhere. No help.

Well, that said, did you check the clutch switch? I didn't see it mentioned in your list.

 

[GAmes]

Did you verify the cable to the throttle linkage isn't broken inside the sheath? Power to the servo is correct, as per the trouble shooting guide in the FSM? I had to fab up jumper wires to do mine.

 

[moparguy]

The servo with the three coils is new as of last week. It’s a oem Mopar item. It could be bad, not high on the suspect list @ the moment though.

Clutch switch, I haven’t checked that. And now that I think about it the clutch safety switch isn’t working. I had the transmission out a few years ago. However I don’t recall if the cruise failed then or not.

Would a jumper in the switch connector be an adequate test?

 

[GAmes]

I'm talking about the power to the servo. not the servo itself.

 

[moparguy]

The cable is connected and good. Power to the servo is another matter. I haven’t checked that and to be honest not sure how. I’ve got a basic no name digital multimeter and a 12v test light and not much knowledge or comfort on all things electrical. Black Magic it is to me.

 

[BigPapa]

I don’t see that the clutch switch is in the CC circuit, but I may be wrong. Yes, you can connect both wires in the clutch switch to bypass for a test. I WOULD NOT recommend leaving it that way, though. The clutch switch is not expensive and easily replaced.

 

[GAmes]

I know that if I push the clutch in the CC disengages. It must be in the system somewhere.

 

[GAmes]

You've owned the truck since new but don't have a FSM? This is from the '96 manual, the only one I have that is digital.

SPEED CONTROL ELECTRICAL TEST
Two different test methods may be used to check
the electronic speed control system. One involves
using the DRB scan tool. If this test method is
desired, refer to the appropriate Powertrain Diagnostic
Procedures service manual.
The other test method will involve the use of a
volt/ohm meter. The volt/ohm meter method is
described within the tests on the following pages.
Refer to Group 8W, Wiring Diagrams for speed control
electrical schematics and connector location.
CAUTION: When test probing for voltage or continuity
at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
When electrical connections are removed, corrosion
should be removed from electrical terminals and a
light coating of Mopar Multi-Purpose Grease, or
equivalent, should be applied.
Inspect connectors for damaged terminals. A poor
electrical connection can cause a complete or intermittent
malfunction. For this reason, a poor connection
may be misdiagnosed as a component malfunction.
VEHICLE SPEED SENSOR
For diagnosis and testing of the speed sensor, refer
to the appropriate Powertrain Diagnostic Procedures
service manual.
SPEED CONTROL SWITCH
For complete speed control system diagnosis, refer
to the appropriate Powertrain Diagnostic Procedures
manual. To test the speed control switch only, refer to
the following:
WARNING: BEFORE ATTEMPTING TO DIAGNOSE,
REMOVE OR INSTALL ANY AIRBAG SYSTEM OR
RELATED STEERING WHEEL AND STEERING COLUMN
COMPONENTS, YOU MUST FIRST DISCONNECT
AND ISOLATE THE BATTERY NEGATIVE
(GROUND) CABLE. WAIT 2 MINUTES FOR SYSTEM
CAPACITOR TO DISCHARGE BEFORE FURTHER
SYSTEM SERVICE. FAILURE TO DO SO COULD
RESULT IN ACCIDENTAL DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
SPEED CONTROL DIAGNOSTIC TROUBLE CODES
Diagnostic Trouble
Code
DRB Scan Tool Display Description of Diagnostic Trouble Code
15** No Vehicle Speed Sensor Signal No vehicle distance (speed) sensor signal
detected during road load conditions.
34* Speed Control Solenoid Circuits
An open or shorted condition detected in the
Speed Control vacuum or vent solenoid
circuits.
55* N/A Completion of fault code display on Check
Engine Lamp.
* Check Engine Lamp will not illuminate at all times if this Diagnostic Trouble Code was recorded. Cycle ignition key
as described in manual and observe code flashed by Check Engine Lamp.
** Check Engine Lamp will illuminate during engine operation if this Diagnostic Trouble Code was recorded.

 

[moparguy]

"You've owned the truck since new but don't have a FSM? This is from the '96 manual, the only one I have that is digital."

GAmes, well technically I do own a '95 FSM. However a few years ago it was loaned out. A few requests were made for it's return, seems it was loaned to someone else and they moved. So, I do own one, just don't currently have it. I do need to shake those trees again. But that said THANKS for the info you shared above. Things to ponder and do.

 

[GAmes]

I have a sign in my shop that says "Don't even THINK about asking to borrow my tools". The '95 and '96 PCMs are different, so the troubleshooting might be different as well.

 

[moparguy]

I’m going to say you need the correct switch.

View attachment 113952 View attachment 113953

BigPapa, my suspicions are in agreement with yours. Particularly since the new '96 only requires 3 wires and the '95 has 4. Now that said, with your superior schematic reading skills, do you see a way the '96 could be made to work?

Thanks for your help.

RonR

 

[BigPapa]

No “superior skills” here. I’ve posted things before that I THOUGHT were correct only to be corrected by someone with “superior skills”. Gary has gently corrected me on more than one occasion.

I don’t see how it could work. From what I see, all functions are commanded on one wire on the ‘96 switch by utilizing different resistors for the different commands. The ‘95 switch puts each command on it’s own wire.

 

[PBJ2500CTD]

BigPapa, my suspicions are in agreement with yours. Particularly since the new '96 only requires 3 wires and the '95 has 4. Now that said, with your superior schematic reading skills, do you see a way the '96 could be made to work?

Thanks for your help.

RonR

Just looking at the differences between the schematics of the two switches I would guess the 96 has a more sophisticated digital switching circuit than the 95. The resistors in the 96 act like a voltage divider and supply the main circuit with discrete voltage values through one wire which activates one of the three circuits, on/off, resume/accel, and set/coast. The 95 uses three separate wires to activate the on/off, resume/accel, and set/coast circuits. It would be a lot easier to replace with the original switch than perform the micro surgery on the 96 switch, hoping the "patient" survives.