Wet/dry vacuum won't suck, won't pick up water, or smells of burning

A wet/dry vacuum usually reaches us with the same mistake: someone left the dry cassette filter in, started picking up water, and the suction died after the first few litres. That is not a motor failure. A wet/dry vacuum (Kärcher, Bosch, Thomas, Nilfisk type) is a different machine from a household vacuum: it has two separate filter sets, a float shut-off, and a tank with a rubber seal. Most complaints come from exactly these parts, not the motor itself.

In this article we walk the same diagnostic order we follow at the bench: filter and float first (the wet/dry trap), then the seal and blockages, and only then the motor. That way you don't spend money on a motor when the wrong filter is to blame.

Suction gone — filters, float, and blockages

Lost suction on a wet/dry vacuum is almost never the motor's fault. Three real causes, by frequency.

Wrong or clogged filter. These vacuums have two modes and two filters. For dry work — a paper or cardboard cassette (pleated) filter that holds fine dust. For wet work — a foam filter, or removing the dry filter altogether. This is the most typical mistake: someone picks up water with the dry cassette filter still fitted. The filter soaks through, the pores clog, air no longer passes — and suction drops to almost nothing. A soaked dry filter is just as bad as one clogged with dust.

Full tank. In wet mode the tank fills fast. A full tank lifts the float shut-off (covered in the next section), and suction stops by design — to protect the motor.

Blocked hose or nozzle. Construction debris, lumps of plaster, the corner of a rag — the hose on a wet/dry vacuum is wide, and a larger object lodges in it easily. On Riga renovations and building sites these machines pull in exactly what they shouldn't: chunks of cement, screws, lumps of lime.

What to check first

1. Take the filter out and inspect it — is it the right one for the mode, is it wet or clogged.
2. Empty the tank completely.
3. Remove the hose and look through it against the light; check the tube joint at the tank lid.
4. Switch on and check suction at the inlet with your palm.

If suction returns after the right filter and emptying the tank — there was no fault at all. We describe the same logic about airflow and blockages in the article on why a corded vacuum won't suck.

Won't pick up water (wet mode and float)

This is where people most often think the vacuum is broken, when it is working exactly as intended.

A wet/dry vacuum has a float shut-off — a light plastic float in the top of the tank, under the motor head. When the water level in the tank rises, the float lifts and seals the air inlet to the motor. That stops suction so water never reaches the motor. It is a protection mechanism, not a fault.

Why it looks like a breakdown:

• The tank is full of water but you can't see it. The float tripped — suction is gone. Empty the tank and it returns.
• The dry filter is still in. With the dry cassette fitted, water soaks it, and the vacuum picks up neither water nor air. Remove the dry filter and fit the foam filter (or run with no filter if the maker allows it for wet work).
• The float is stuck in the up position. If the float is caked with dirt or limescale, or jammed in its basket, it stays up and seals off suction even with an empty tank. Take off the motor head, find the float, and check with a finger that it moves freely up and down.
• The float basket is clogged. There is a mesh basket around the float; if it fills with foam or debris, the float trips too early.

The DIY boundary here is clear: choosing the right filter, emptying the tank, and cleaning the float are the user's job. If the float is broken or the seal ring under the motor head has crumbled — that is service work.

Leaks water or blows dust back out

Two opposite symptoms, one field of causes: the seal and the filter.

Water leaks from the tank joint. A wet/dry vacuum has a rubber seal (seal ring) between the motor head and the tank. Over time it hardens, cracks, or sits crooked — and in wet mode the water pressure and foam start to seep out along the edge of the joint. Check that the seal is in place, clean, and supple; a hardened or torn seal must be replaced. Baltic humidity and building-site dust tire this seal out faster than you'd like.

Blows dust back into the room in dry mode. This means fine dust is passing through the filter instead of staying in the tank. Causes:

• The filter is torn or holed — dust goes straight through.
• The filter isn't seated correctly, so air goes around it.
• The foam filter was used for wet work, then switched to dry mode without refitting the fine cassette filter — dust flies out unfiltered.

In older Riga apartment blocks with dry heating-season air, this blow-back is especially noticeable: fine dust hangs in the air longer and settles visibly. The fix is always the same — an intact, clean filter matched to the mode, seated firmly in place.

Won't switch on or trips the breaker

Before you think about the motor, work through the simple causes.

Two Riga-specific notes. In older residential buildings with aged wiring, a powerful shop vacuum can cause voltage dips or trip a weaker breaker, especially if another high-draw tool is on the same line — check whether the problem appears only at one particular socket. Second, if the cord is damaged right at the plug or where it enters the body (the classic bend point), the motor may start with a stutter — that's a cord question, not a motor one, but the repair still belongs at the service centre.

If the simple causes are ruled out and the vacuum still won't respond — there's an electrical fault inside (switch, winding, broken lead), and that is solved at the bench.

Burning smell or a loud motor

This is the only section where it really is about the motor — and it is serious.

A wet/dry vacuum motor is air-cooled: the same air it draws in cools the windings at the same time. So a burning smell almost always means the motor is running without enough cooling, or water has got into it.

Burning smell, motor running at a normal noise. Most often — a clogged filter or tank, airflow blocked, windings overheating, and the insulation varnish starting to smoulder (the characteristic smell of heated varnish). Switch off first, let it cool, clean the filter and tank. If the smell returns after that — the motor has suffered.

Loud, growling, or vibrating motor. This is mechanical wear: worn carbon brushes (in brushed motors) or worn bearings. The noise builds up gradually over weeks or months. Brushes and bearings are replaceable, but that is done at the service centre with the motor dismantled.

Sharp, wet burning smell after picking up water. The worst case: water has reached the motor — usually because the float didn't trip (stuck down or broken) or too much water was pulled in with a faulty float. Water in the motor means oxidation, a short, and usually a motor replacement.

Safety line: if you smell burning or see smoke, switch off and unplug at once. Never keep picking up water with a vacuum that has already let water reach the motor — that is an electric-shock hazard.

A clear DIY ↔ service boundary for the whole motor block: fitting the right filter, emptying the tank, checking the float, and replacing the seal are the user's job. Anything that needs the motor head dismantled — brushes, bearings, winding, a water-flooded motor — is bench work at the service centre.

Is a wet/dry vacuum worth repairing? (decision table)

These vacuums typically last 4–6 years of active use before the first serious complaint appears. The "repair or bin" call depends on exactly what has failed.

Filter, float, seal, and hose problems are almost always worth solving — they're quick and the parts are available. Motor problems we assess case by case: we identify the fault on-site, because what matters is whether the motor is merely worn or already flooded.

We repair wet/dry and shop vacuums alongside household and robot models — for the scope of diagnostics and service, see the page on vacuum repair in Riga.