PacBrake

[brothers8]

Hello Friends, My 1996 Safari,Cat 3126, AWT 6 Speed, pac brake activates every time you use the service brakes even if the pac brake is turned off. I disconnected the brake lights @ the momentary switch and all is well except no brake lights of course. Im having a hard time tracking there it is tied in, I have been using a pulse wire tracker but having little luck. Any one heard of this? 

[manholt]

brothers8.  Welcome to the Forum!

Unfortunately, our CAT expert is in South Chile at the moment (not in RV) and he won't return until 3/30/18.

We have a member on the forum...BILLEDWARDS look him up and send him a personal message...he's got 2 Safari's.  Right now he's in the Quartzite area boon docking!  The other would be DickandLoise.  

[brothers8]

Thanks for the note on Bill Edwards, Im new to FMCA how do I contact him?

[obedb]

Have you considered the possible failure of the on/off switch for the PacBrake? Our's would require a small Phillips screwdriver to be able to lift the switch panel to check the circuit.

[wolfe10]

Bill Edwards contact info: http://community.fmca.com/profile/22868-rsbilledwards/?wr=eyJhcHAiOiJmb3J1bXMiLCJtb2R1bGUiOiJmb3J1bXMtY29tbWVudCIsImlkXzEiOjExNDgxLCJpZF8yIjo4OTA4NX0=

To send him a message, click on the "envelope".

One of two issues:  your coach has a brake signal to the Caterpillar ECM AND, repeat AND, it has been programmed for LATCH MODE (exhaust brake comes on when service brake is applies and stays on until the throttle is applied) OR you have an after-market brake relay that does much the same thing.

Yes, you could have a relay sticking causing this as well.

[brothers8]

Those are both excellent replies and I have considered both,  The first reply,  on /off switch. I need to do more fault finding on this. I have the panel open and have tested the switch. I need to  do more testing to be sure of the outcome ,Thank you for the input. The second reply,  Thats what happens,  throttle on disables exhaust brake. The ECM has been replaced  and I was thinking it was a reprogramming issue between TCM and the ECM?  I have not seen evidence of a brake relay replacment but I need to trace relays on the pac brake for light signal  ????????? Thank you for your time Guys Keep you posted...... PS In looking @ wiring diagrams on -pacbrakes site, non have brake lights tied to exhaust circuits? ..........

 

 

[manholt]

brothers8.

If your exhaust brake comes on when you use your brakes, then your brake lights should be on.  My coach has a manual on/off toggle switch, if I engage it, then it will stay on and slow me down on hills or flat regardless off me stepping on brake or not.  If I'm not on brake petal, then no light.  If you follow a 18 wheeler down a steep grade and it has exhaust brakes, his brake light will only come on when he step's on brake, as he will also be in a lower gear.  My Allison will automatically go into lower gears as I decelerate by the combination of brakes.

 

[wolfe10]

Yes, the Caterpillar ECM can be configured several ways in terms of activation of the exhaust brake.

Manual is one-- only comes on when the electric switch for the PacBrake is turned on.

Latch--  Comes on when you step on the service brakes.  Stays on until you step on the throttle whether you remain on the brake pedal or not.

There is one other choice, but I don't have my manuals handy right now.

Any Caterpillar dealer could tell you how yours is configured in 5 minutes by plugging into the diagnostic plug.