Follow along to see the possible reasons and fixes for why your blasting continues after you release your Blast Control Switch.

1. Contaminants or failed O-Rings on the spool of the air-relay.

2. Clogged breather vent in the air-relay exhaust port.

3. Clogged in-line filter at the dead man return bulkhead

4. Faulty micro-switch in the electric Blast Control Switch.

1. Secure the blast hose.  With the unit blasting and the Blast Control Switch released, observe the blast pressure gauge.  

A. If the pressure on the gauge is slowly decreasing (and the unit eventually stops blasting), remove the breather vent, and see if that clears the problem. 

B. If so, thoroughly clean the vent or replace it - do not leave the port open because dust will get into the spool.

2. Secure the blast hose.  With the unit blasting and the Blast Control Switch released, observe the blast pressure gauge.  

A. If the pressure on the gauge does not change and the unit continues to blast, engage the e-stop (push it in).

B. If the unit stops blasting, the problem could be a clogged in-line filter at the Blast Control Switch return bulkhead OR a faulty micro switch in the electric Blast Control Switch. Unplug cord for Blast Control Switch at the recessed plug. This will determine which of the above possibilities is at fault. Repair according to finding.

3. Main air regulator piston is not seated.

A. Engage the e-stop (push it in).  If the unit does NOT stop blasting, the problem could be contaminants in the main air regulator - keeping the piston from seating.

B. First, secure the blast hose.  Apply air pressure from the air source and then depress the Blast Control Switch.  With the BCS handle depressed, turn the blast pressure regulator gently to maximum.  Release the BCS and see if the unit stops blasting.  

C. If not, shut off the air supply and continue to next step. At the main air regulator, remove the piston cover and carefully pull the piston out of the regulator body.  Be sure not to damage the shaft.  Clean out any debris, re-lubricate the piston shaft and reassemble and re-test.