BC 400 IV Cummins Jake brake

I recently picked up a 1988 peterbilt 378 with a 400 Cummins in it. Engine brake was disconnected on it.
Hooked it up today after chasing and testing wires. Spring on the clutch return had fallen off and the previous owner disconnected the wires at the pump (I imagine it was kicking on the Jake when he hit bumps).

I only have 2 out of 3 stages/heads kicking on. With the switch in position 1 I get nothing, in 2 I get 1 solenoid to work and in 3 I get 2 solenoids to work.

Does anybody know which head has the 1st solenoid (front, center or back)?

 

Thanks for the replies. I figured the order was center, front, rear but wanted to double check. It will be too cold out tomorrow for me to check but I guess it would be wise to check power to each box before I pull the cover off the center housing.
I understand how to test the solenoids but didn't want to pull apart all three housings if I didn't have to.

I assume the Jake hasn't been hooked up for a while, any chance the solenoid could be stuck shut similiar to how a nitrous solenoid can get clogged?

 

Okay I got outside and did some testing.
switch on stage 1:
No hot wire to any of the housings
switch on stage 2:
Center housing hot
Switch on stage 3:
All 3 housings hot

So somebody rather has the switch wired wrong or the switch is crapping out. I'll pull the dash back apart tomorrow to figure it out.


And I spoke to the local peterbilt dealer. for any future reference related to these 3 stage switches the correct order is:
Stage 1 is center.
Stage 2 is front and rear.
Stage 3 is front, center and rear.

 

Fixed. They had every wire in the wrong spot on the switch. Didn't start it to confirm solenoids are working but the wiring is correct and key on, wiring to housings light up in the proper order. Don't want to start it on Sunday and smoke out the neighbor.

 

Well I get along with the neighbors and don't want to fill their yard with smoke haha.
I should be able to tell pretty easily if all the solenoids work, stage 1 will be center, 2 will be outboard heads and 3 should be louder than 2 (and is working if 1 and 2 work).

Tomorrow the new led turn signals go on, gotta weld up a buddy's bedside on his truck and then tackle the headlight issue on this truck later this week.