"BrakeSwitch" Exhaust Brake Controller Installation
David E. Damouth www.damouth.com
22 June 2006
Introduction
The operation of the exhaust brake in our Winnebago Journey motorhome has been a minor but continuing source of annoyance. If the exhaust brake is enabled, it is very difficult to coast since as soon as my foot comes off the accelerator, the exhaust brake comes on, the transmission downshifts, and strong braking results. It is possible, although difficult, to coast by keeping the accelerator just very slightly depressed. Also, when the cruise control is on and the exhaust brake is enabled, the brake will turn on and the transmission will downshift on even the slightest downslope, as for example coming off an expressway overpass on otherwise level terrain.
For these reasons, I have been turning off the exhaust brake during normal driving. But it is desirable to have the exhaust brake constantly enabled, so that it is available for emergency stopping without having to grope for the exhaust brake switch when an emergency stop is required. If turned on, the exhaust brake is also helpful in reducing brake wear during normal stops. But turning it on manually every time I want to stop is a nuisance.
To fix these problems, I purchased the "BrakeSwitch" exhaust brake control module from www.brakeswitch.com. This is, in my opinion a major improvement in exhaust brake convenience and usability. It costs $84.90 including shipping. See the above website for details.
With this device, the exhaust brake can be left always turned on, and its operation is automatic and intuitive under all driving conditions.
With the BrakeSwitch installed, I leave the exhaust brake enabled all the time. When I remove my foot from the accelerator, the exhaust brake does not come on, and the motorhome coasts, slowing gently. If I want to decelerate more rapidly, I touch the brake, turning on the exhaust brake. When I again touch the accelerator, the exhaust brake turns off. I love it! My wife loves it! Why aren't all exhaust brake controls designed this way?
The installation instructions that come with the product are a bit vague, because of the many different wiring variations found among the various brands of motorhome. What follows is specific to my 2002 Winnebago Journey 32TD, although I suspect that other Journey models and years will be very similar.
Installation
1: Remove the housing behind the instrument cluster. It is attached with five screws along the base of the housing toward the windshield, and three little black screws at the right edge. With this housing removed, all the wiring to the gauges and switches on the instrument panel become accessible. 
2: Unplug the connector from the back of the exhaust brake switch. The location of the switch makes it difficult to get a good grip on the connector. I found that I could grip and pull on the upper portion of the connector with one hand, while prying outward on the inner bottom edge of the connector with a flat-blade screwdriver with the other hand.
The exhaust brake switch is a double-throw double pole switch, but it is used only as a single-throw switch. Nothing is connected to the upper row of pins. The left middle pin connects to the left lower pin with the switch on, and the right middle pin connects to the right lower pin with the switch on.
The connector has 8 connections - four rows of two. Note that the second row from the top has no connections, and the top row does not make contact with any switch pins (even though it does have wires running to the connector pins). So only the four wires on the bottom two rows of the connector are functional.
3: The wires on the second row from the bottom are the ones of interest. Both are white on my rig. See Figure 1. This is drawn looking at the face of the connector which mates with the switch. The white wire on the right has 12 V. with the ignition ON and 0 V. with the ignition off. Cut this wire and splice each cut end to the two white wires from the BrakeSwitch.
4: The white wire on the left (labeled "RETARDER" comes from the ECM. Cut this wire and splice the cut ends to the two red wires from the BrakeSwitch.
5: The purple wire from the BrakeSwitch must be attached to a brake signal, which is 12 V. with the brake pedal depressed and 0 V. otherwise. I found an easily accessible source of this signal on a connector at the bottom of the steering column. 
This connector is a black cylinder with seven pins, from which the wires go up the steering column to the turn signal lever. The center pin on the chassis harness side has a white wire labeled "OVERRIDE 35H 37 3GA3290". On the steering column side, this connection is not used - there is just a few inch of wire coming out of the connector and hanging loose. I connected the purple BrakeSwitch wire to this stub.
6: The black wire from the BrakeSwitch is connected to chassis ground. I used a sheet metal screw both to attach the BrakeSwitch module to the dashboard frame and also as a connection for the black wire, after verifying that this frame was a good ground.
This completes the wiring. The photo shows the wire splices and mounted BrakeSwich module, before re-installing the connector on the exhaust brake switch. Cutting the BrakeSwitch wires down to just the length needed would have made a neater installation, but I chose to leave them full length in case I ever want to re-use this module on a different vehicle.