89SP, with allison xmission, retarder doesnt work w/dash lever, does w/dash sw.

[wl89spman]

The dash switch is 3 position rocker. Center positoin is OFF, left position is
ON, right position is APPLY. Retarder used to work but quit a couple of years
ago. With sw in ON position, lowering the dash lever does nothing now, but when
switched to APPLY position, an immeadiate slowing down as if braking. When in
APPLY position I think its an electrical signal to the xmission, but when in ON
position it takes "AIR" from the dash lever to activate the retarder, therefore
I think it's an air problem.
Anyone agree or had this problem? Where do I start? Any suggestions?
Thanks in advance for any help!!
Ed Gardels 89SP
Arlington
egardels@...