[77newell]

I've had some experience with this on my 77 coach. Hopefully this will help. The dash switch supplies 12 volts (when in the "on" position) to the buffer switch. The buffer switch turns "on" whenever the governor enters a no fuel situation (this would occur when the engine is over-running the governor setting). When the dash switch and buffer switch are both "on" then power is sent to the solenoids inside the rocker box covers to alter the timing of the exhaust valves so that braking occurs. The adjustment of the buffer switch is critical. If it adjusted too far out then no braking will be available. If it is adjusted too far in you will have fuel being injected by the injectors while opening the exhaust valves early. If this happens very long you will hear your wallet getting lighter.

If I recall correctly you can(with the engine stopped and the dash switch "on" mechanically trigger the buffer switch to ensure it is operating. This switch can occasionally die and you don't want to mess with the adjustment until you are sure it is working. If it is working, then you want to make tiny adjustments. If you go slow you will not harm the engine. In my case all it took was 1/8-1/4 turn to go from too far to just right. I would suggest downloading the manual from the Jake website which will show pictures of the process I just described. Adjusting inward will make the Jake come on earlier and adjusting out will make it come on later or eventually not at all.

It is a very simple system, there is no control box, just a couple switches and some solenoid valves.