3406B Cat Jake Break & Retarder wiring

Power actually comes in from the ign side of key switch through the clutch switch to the fuel pump switch. Leaves pump switch to the switch on dash leaves the switch on on dash to Jake heads

 

I'm not sure on the location in a KW, but there is a pressure regulator for the retarder somewhere behind ir under the dash. You should be able to chase the airlines from the retarder handle down to the regulator. Our Pete has a electric over air switch to run the retarder off the switch like a Jake, and it is in conjunction with the regulator. The wiring to the air switch should be the same as the Jake. When using the switch on the dash rather than the lever, you will get full pressure (whatever the regulator is set at, and it is adjustable) all the time. At least that is the way they are on our 89 Pete's.

Edit to add:

I didn't answer your question. @wore out described how the wiring to the Jake should be. I believe you should be able to tap into the wire coming into the Jake switch, and power the retarder switch from that.

 

That is why it’s wired backwards in some folks eyes so that one circuit could run both brakes on 2 switches. Putting a splitter coming out of the power in to the Jake switch would work but isn’t the right thing to do technically. Also would want to insure that power goes through clutch switch to fuel pump switch first as well. The Jakes should loose all power at the switch by touching accelerator or clutch.

 

Yes if you take the positive from that feeds the Jake switch and feed the retarder switch. With retarder off and Jake on the retarder switch should not have power out of both legs. With retarder on is only time the switch should have power on both legs. I have seen the air over electric switch stick in the on position or the wrong type air switch used. Getting it back “right” would be best even if troublesome rather than wiring it up to work

 

I guess I was thi

I guess you would have to install an old style Cummins push button fuel switch on the throttle linkage to keep them separate as the fuel switch has spade connectors, and the circuit would end up joined there anyway?

Our blue truck has both jakes and retarder, but no electric operation of the retarder. The white one only has a retarder, and can be operated either with the hand valve or by electric switch, so neither of them have dual electric operation, and I don't have an example of how the factory would do that.