Use a Cruise Buttons to Control E-Brake?

[Doc Tinker]

Is it possible to use one of the right hand cruise control buttons to operate the e-brake. Any suggestions on how to rig it?



Doc

 

[15w40]

It's all possible with electronics!

The speed control in my 98. 5 (may be the same for other years) uses resistors in the steering wheel to tell the PCM which button has been pushed. RESUME/ACCEL, and COAST are on the right side and will momentarily switch one of the resistors between Ground and Speed Control Switch Signal on the power train control module. Hitting CANCEL directly Grounds the signal to disable the speed control. The problem with using any of these switches to control the exhaust brake is that any electrical load added to any switch will change the value of the measured voltage. In other words if you tried to use the button to activate a relay and energize the exhaust brake, the resistance of the relay coil would throw off the voltage measured at the PCM with some unknown result. Maybe ACCEL???



A way around this added load problem could be to use a chip to unload the circuitry. An IC chip such as a comparator used to drive a relay should work but not without some experimentation. The simplest button to use would be the CANCEL. About $5. 00 in parts from Radio Shack and it can be done. If you are interested in pursuing this let me know and I will post a schematic.

 

[Doc Tinker]

I'm interested in it. Actually, the cancel button would be the logical one to use, since I would normally want to engage the e-brake when I cancel the cruise to slow down.



If I'm on the eway doing eighty and the radar detector goes off, I hit the cancel button immediately Having the e-brake kick in at that moment would be even better. You think they can be set up to work together?



My original intent was to eliminate the use of one of the buttons for the cruise and use it just for the e-brake.



Doc

 

[Chipstien]

Sweet idea Doc, I would love to see if this is do-able.

 

[15w40]

Doc,

Let me start by telling you I don’t have an exhaust brake on my truck but from reading this web site I think I know how they work. The exhaust brake will activate when an enable switch has been turned on and the accelerator pedal has been released. If this is incorrect, my answer to using the cruise buttons may not be correct. Also my wiring is from FSM for my 1998 2500 and things my change from year to year. Anyway, enough of the disclaimers and on to the answer.



All of the cruise control buttons on the steering wheel connect to the PCM on the firewall, using only two wires. These two wires are routed through the clock spring at the steering column. One wire, Sensor Ground, is on connector A pin 4. The other wire, Speed Control Switch Signal, is on connector C pin 32. To identify these connectors on the PCM, connector A is black and is on the right when standing in front of the truck. Connector C is gray and is on the left. Just as a reference, connector B is white and is in the middle. These connector colors are part of the PCM. Don’t confuse them with the colors of the plugs attached to the PCM.



If you NEVER want to use the cruise control the answer is very simple. The only component needed is a relay to activate the exhaust brake and a diode to absorb the relay inductive kickback. This can be any general-purpose 12-volt relay. The reason for using a relay is the steering wheel buttons are not designed to switch much current. The relay will keep the current low to the button. I am holding one of Radio Shack’s 30 amp lighting relays in my hand so I will describe the connections to it. Cut the wire connected to connector C pin 32 on the PCM. Connect it to one of the relay coil connections, pin 86 on my relay. Connect the other relay coil connection, pin 85 to a switched +12 volt source. The remaining two pins on the relay, pin 87 and 30 are wired in place of the cab mounted exhaust brake enable switch. The previously mentioned diode can be any general-purpose diode such as 1N4001 on 1N4148, also from Radio Shack. Attach the banded end of the diode to relay pin 85 and the other end to relay pin 86. The diode may not be necessary but to be nice to the electronics, it’s a good idea to clamp the voltage spikes.



To operate the exhaust brake you will now have to hold down the CANCEL button as you let off the accelerator. The relay should activate when the CANCEL button is pushed and will release when the button is released. This takes the place of the switch previously used to activate the brake.



Now if you want to retain the cruise control functions disregard all of the above and do not cut any wires. The answer now gets slightly more complicated because an n IC is needed to “unload” the cruise control circuit. I have worked out a fairly simple circuit but I need to make some measurements on my truck and it’s raining outside. Stay tuned for the next post in a few days.

 

[Mundgyver]

I'm not sure about your year of truck, but with mine, I installed the e-brake and it works with the cruise control just fine. It pulls it's singal from pin 20 on the engin computer connector. If you have cruise engaged, the throttle will keep it from activating. Once you start down a hill and the throttle lets up, particularly with a load, 1 1/2 seconds and the e-brake comes on. If I hit the cancel putton it will come on. Totally automatic. The delay that it has, is to alow you to shift gears. . On a cross country trip, if I set the speed to 65, between the cruise control and the e-brake, I stay right there. It is a wonderfull set up. I'm getting ready to order the flasher lights for the third brake lite and put those into the e-brake circuit so when it comes on my tail lights will automatically kick in. Oo.

 

[KatDiesel]

How about the new steering wheel commander gizmo from Geno's? It seems that wouldn't be to hard to wire up and it leaves your cruise control free and clear for its intended use. I don't have one just thinking out loud.



Just looked at Geno'sGarage website, I can see the price is not cheap, so I could see why you wanted to wire the cruise control.



Good luck with it!

 

[RottnDogue]

WOW Doc has a good idea... ... . Someone alert the Press... ... :-laf :-laf :-laf :-laf

 

[carson6]

Hey Guy's

I would like to run mine in the gear selector lever if it is hollow and put the e-brake switch at the end ?? can this be done on a 97??

 

[Evan A. Beck]

Carson,



On your '97, you could upgrade the shifter to a '98+ version. This will allow you to use the button that is already in the end of the shifter. You'll need to use a latching relay to active the brake, but that is easy to do. I have retrofitted the '98+ shifter to many '94-'97 trucks. It's pretty easy to do.

 

[MikeR]

Hey Doc,



Just like Mundguyver said, there is no need for all thay fancy switch stuff. Just turn on your exhaust brake switch, set your cruise and be on your way. As soon as you hit cancel, the accelerator pedal goes to the idle position and your exhaust brake engages. This is how all brands of exhaust brakes already work.

 

[Michael Hughes]

I think some of you have missed the point. Doc is wanting to use on the of the cruise buttons to turn the ebrake on and off. He doesn't want to have to reach down to do that and doesn't want a switch on the shifter. His question has nothing to do with the cruise.

 

[LarryB]

How hard is it to reach for the switch? Oh, maybe that's not the point, sorry. :-laf :-laf :-laf

 

[Joe G.]

I certainly missed the point alright. What is wrong with just turning the e-brake on and leaveing it on? Any time you press the pedal the e-brake lets go. When you lift it engages. I turn mine on as soon as I start up and turn it off when I stop to shut down.

 

[Michael Hughes]

It is nice to be able to turn it off while at a stop light. I have a switch on the shifter.

 

[Doc Tinker]

LOL - Yes, I don't want to reach for the switch. I remember a time when I had to drag my foot to slow down my bike. Now I'm so spoilt that I can't reach for a darn switch. And it would be nice to turn on and off the cruise independantly from the cruise.



Doc

 

[Doc Tinker]

I don't like to idle at the light with mine on. And with the stick, it's not too cool to let the ebrake kick in while shifting, so when I have to slow down I shut it off until I'm back up to speed again.



Doc

 

[Mundgyver]

Question for Doc. Are you running an automatic or a stick. Reason behind the question is that I have a stick. In town, I do get tired of leaning forward and hitting the switch. I am planning on getting a Gear Vendor Overdrive unit. Gear Vendor makes a lift switch that looks like the old switch for the two speed rear ends of 40 years ago. They use this switch on the shifter to activate their over drive. Looks like one in a semi. If you have a manual transmission, you could put one on the stick and use it there since you would be shifting anyway.

If you have an auto then the remote switch that Genos sell would work, but it is very pricey. What you might want to consider is finding a cheap cruise control stalk that some of the early cars had where the button is on the end. Take the whole stock and mount it to either you turn signal or Automatic shift handle and work it that way. Just an idea.

I understand the ability that you would want to just instantly turn it on with out a lag. That would be handy.



-

14 Mundgyver -

 

[LarryB]

I have the shifter switch for my BD brake, I wouldn't have it any other way. I added the USGear 2sp button and it's great too. I've only tried to shift the e-brake a couple of times and when slowing once I upshifted the 2sp. I'm getting used to it though.

 

[Mundgyver]

Nice set up. That's what I'm looking to put in mine.