Cruise control not working correctly, clock spring is new

[GrossmeisterB]

Hello everyone,

as I said in my introduction post, I am new to the RAM trucks and bought a 2004 RAM 1500 HEMI 4x4.
The clock spring was defective, as is the horn push button, so someone disconnected the horn switch and installed a seperate horn with switch.
Now I replaced the clock spring and the horn is working, so is the cruise control, but only sometimes.
What I found out:
below 20mph I can switch it on (dashboard light "cruise" is on), but pressing the "set" button does not do anything.
Above 20mph it is working as it should, but not all the time. Sometimes it will engage, but not always.
Going above 40mph I can't even switch it on (dashboard light "cruise" will not come on) and if I switch it on below 40mph and go over 40mph the light will switch off and the cruise control will disable itself.
So, what could this be? I heard it might be the brake light switch or the front left wheel speed sensor?
Thanks for any input!

 

[GrossmeisterB]

I replaced the brake light switch, the front left wheel sensor and the gearbox speed output sensor, but no change in the behaviour.
No one got an idea? How can I test it maybe?

 

[Daw14]

Cruise will not engage under 20 or 25 mph ,so that eliminates that part . Have you checked for codes ? I would lean towards wheel speed sensor/s , not sure what you have for them. Always use OEM sensors or the same brand it came with new.

 

[GrossmeisterB]

Yeah, I already thought it wouldn't engage below a certain speed though.

I checked for "c-codes" with the instrument cluster, but no codes there ("00 00" only), read engine codes with an OBD reader but no codes there neither...

What I read elsewhere is that it is important to use the correct wheel speed sensor as there are different types (3 different part numbers in the parts catalogue) for 1500, 2500 and 3500 RAMs.

I have no clue if my "old" (original/stock) sensor was defective though.
But the control module might sense a different speed between the front wheel speed sensor(s) and the rear speed sensor and switch it off?

Also, which sensor do control the cruise control part? Do you know that maybe?

Thanks for your help!