Guides & Troubleshooting
Field guidance for B/Mc spray valves.
Valve weeps when closed
Most often the rubber ball or the diaphragm. Both are in the rebuild kit. Inspect the seat while it is apart — a damaged seat will defeat a new kit.
Valve is slow to close
On air valves, check the quick exhaust (03-011) before condemning the spring. A restricted exhaust makes a healthy valve look tired.
Electric valve will not actuate
Confirm coil voltage matches the truck — 03-016 is 12V, 03-018 is 24V. Then check the strainer (03-017); a blocked strainer starves the solenoid.
Adjusting spray pattern
Pattern and Volume are set at the adjustable Bertolini Band.
Before you start
Work through these in order. Most B/Mc valve complaints come down to one of four things: the wet end needs a rebuild, the exhaust is restricted, the coil is getting the wrong voltage, or the strainer is blocked. Confirm which before ordering parts — a rebuild kit will not fix an electrical fault, and a new coil will not fix a worn seat.
Valve will not open — air
Check supply pressure at the valve rather than at the tank, then confirm the quick exhaust 03-011 is clear. If air is reaching the valve and it still will not lift, the diaphragm 03-006 is the usual cause — it is in the rebuild kit 70-064.
Electric valve does not pull in cleanly
Confirm the coil matches the truck before anything else: 03-016 is 12V and 03-018 is 24V. Then check the strainer 03-017, because a blocked strainer starves the solenoid and makes a healthy coil look faulty.
Water leaking around the lid
Check that the lid clamp 03-004 is seated square and fully tightened before replacing anything. If it is, look at the urethane washer 03-027 next. A distorted lid 03-010 will not seal no matter what sits underneath it.
Side spray not working
The side spray attachment 03-002 has its own gasket 03-014. If the main spray works and the side does not, start with that gasket — it is the least expensive part in the system and the most common cause.
What to have ready before you call
- Whether the valve is air or electric, and if electric, 12V or 24V
- The Randco part number if you have it — see the cross-reference table
- What the valve does now, and what it did before
- Where the valve sits on the truck: front, rear, driver or passenger side
Found the part you need?
Every part named above is stocked and shipped by Randco Tanks. If the fault is not listed here, the parts desk can work through it with you.