Overview
Side-mount reed float switch with bulkhead fitting. HydraMaster part number 000-157-031, listed as Switch, Side Mount w/ Bulkhead Fitting.
It mounts through the tank wall rather than through the lid, and senses level with a float running on a reed switch. On a truckmount it is normally sensing water box level, mix tank level, or a low-water condition.
What it fits and how many
HydraMaster's suggested spares schedule lists it against the Boxxer 421, CDS 4.6 / 4.8, MAXX 450D / 470D and SpitFire 3.2. Named in the parts lists of:
- Boxxer 421 — 1 fitted, water box assembly item 4
- CDS 4.8 — 3 fitted
- SpitFire 3.2 — 3 fitted
- MAXX 450D / 470D — 1 fitted, water box assembly item 17
- CDS 4.2 / 4.7 — mix tank assembly item 21
- CM402 — 1 fitted
Check how many your machine has before you order. A CDS 4.8 and a SpitFire 3.2 each carry three; a Boxxer 421 carries one. If one has failed, the others have done the same hours.
Diagnosing a float switch
A reed float switch fails in two ways, and they look very different from the operator's seat.
Stuck closed — the machine thinks the tank is at level when it is not. This is the dangerous one, because whatever the switch was protecting keeps running.
Stuck open — the machine reports a fault or refuses to run when the tank is actually fine. Annoying, but it fails safe.
Before you condemn the switch, check the float. Scale, fibre and detergent residue build up on the float and the stem, and a float that cannot travel freely reports the wrong level with nothing wrong electrically. Clean it and try again.
Then check the wiring. Reed switches are sealed and reasonably robust; the connections in a wet tank environment are not.
Fitting advice
Note the orientation. A float switch fitted upside down works exactly backwards, and it is an easy mistake to make on a bulkhead fitting that will thread in either way.
Seal the bulkhead properly. A weeping bulkhead fitting on a water box is a slow problem that becomes an electrical one.
Where the machine has more than one, mark which is which before you remove anything.
Related parts
- HydraMaster Recovery Tank Float Switch (157-0801) — the polypropylene barrel float switch with protector, used in the recovery tank
- Liquid Level Mini Switch (157-004)
Frequently asked questions
How many does my machine take?
One on a Boxxer 421 or MAXX; three on a CDS 4.8 or SpitFire 3.2. See the list above and check yours.
Does it include the bulkhead fitting?
Yes — HydraMaster's description is side mount with bulkhead fitting.
Is this the recovery tank float switch?
No. The recovery tank uses 157-0801, the polypropylene barrel float with protector. Different part, different location.
My machine reports low water with a full tank. Is the switch dead?
Clean the float and stem first. Fouling is a more common cause than switch failure.
Tell us the machine model and where the switch sits and we will confirm which float switch you need before you order.
