Ned Simmons fired this volley in
:

Sounds like the solenoid valve is not shifting properly. The spool is
getting stuck in an intermediate position when you try to apply the
brake. Look for a manual override on the solenoid -- it may be a very

I don't think so. I think you have a torn o-ring on that valve's spool.

It's normally easy to fix, Ig. If it's an Ingersoll-Rand style of valve,
there's a snap ring on one end that when removed allows the spool to slide
out. You replace the o-rings (all of them) clean and re-grease the bore,
and slide it back in.

LLoyd