RQ755-DC21V Motor for FOX EXPERT Cordless Trimmer

A silent trimmer is not a reason to buy a new one

The motor in a cordless trimmer is a wear part. It is not designed to last forever: a brushed motor has a finite brush life, the bearings do not tolerate impact, and the windings do not forgive overheating. The good news is that replacing the motor is by far the cheapest way to bring a trimmer back to life. A new tool costs several times more, while the whole job comes down to two screws and two terminals.

RQ755, not the base RS755 - what actually differs

This is the key difference between this part and anything sold under the generic label "RS-755 motor". What we supply is the updated RS755 to RQ755 series, which brings two design improvements:

• A built-in plastic cooling impeller. Overheating is the number one killer of brushed motors. The impeller drives air through the housing during operation and keeps the windings off their critical temperature when you are cutting dense grass.
• Longer-life carbon brushes. The brushes are what determine how many seasons the motor survives; on the base series they wear down noticeably faster.

Off load, the motor runs at 13,500 rpm. The operating voltage range is 12-21 V, continuous current 1.9-2.4 A, output power up to 300 W.

Why these motors fail, and how to avoid it

Based on customer reports, there are exactly four causes, and every one of them is preventable:

1. Water. The motor is not sealed. Cutting wet grass, dew, rain and above all hosing the trimmer down will destroy the motor quickly and permanently.
2. Over-tightened cutting attachment. The most common and most avoidable cause. The blade or spool is tightened so hard that the shaft cannot spin freely. The motor then runs close to a stalled condition, current rises, and the windings overheat. Tighten it firmly but without force: once fitted, the attachment should still turn freely by hand.
3. Impacts against stones and kerbs. Shock loading destroys the bearings. The shaft then runs out of true, and you get noise and vibration.
4. The knock-on effect: a shattered impeller. A hard impact can break up the plastic cooling impeller, leaving a motor that still appears to run but has no cooling at all. After that it is a matter of a few hours of cutting.

If your old motor hums, vibrates, or runs hotter than it used to, the cause is almost certainly on this list.

M5 right-hand thread: the spec that most often makes a motor not fit

The motor shaft carries an M5 right-hand thread (standard, clockwise). This matters: motors of the same physical size exist on the market with left-hand threads and with plain splined shafts, and that is exactly why buyers end up with a part they cannot assemble. We state the spec openly so you can check it against your tool before ordering rather than after. Shaft diameter is 5.0 mm, with 27 mm of output shaft.

Fitting: no soldering, and protection against reversed polarity

On this model the connection is made with spade terminals - no soldering iron required. The wires simply come off the old motor and push onto the new one. The motor is held by two M4 screws with 29 mm between centres, and the housing is 44 mm in outer diameter.

On polarity: a red dot marks the positive terminal. Use it as your reference. If the wires are reversed, the motor turns the wrong way, the attachment will not cut, and the shaft thread starts undoing itself during operation.

A straight answer on voltage: 24 V, 36 V and 48 V batteries use this same motor

The question we get most often is whether this motor will fit a 48-volt trimmer. It will, because there is no 48 volts in it. Trimmers are widely sold with batteries labelled 24V, 36V, 48V and even 96V, and inside every one of them is the same 12-21 V RS(RQ) 755-DC21V motor, running off the same 21 V lithium pack.

It is easy to verify: measure the battery with an ordinary voltmeter. For reference, a genuine 48 V pack would weigh at least 7 kg and would take three to four days to charge from your standard charger. We say this plainly rather than staying quiet about it, so you do not spend time hunting for a part that does not exist.

Compatibility

This motor is the standard fit for the FOX EXPERT cordless trimmer. Please note that the FOX Professional range uses a different, brushless motor, and this part will not fit it.

Beyond that, the RQ755-DC21V is a widely used size found in many 21 V cordless trimmers and grass cutters; it is listed, for example, as the motor for the Procraft PTA24. If you are matching it to another tool, check four figures: 44 mm housing diameter, 29 mm between the M4 mounting holes, a 5 mm shaft with an M5 right-hand thread, and 27 mm of output shaft. If all four match, the motor will fit.

Who it is for

For FOX EXPERT owners whose motor has reached the end of its life or has been damaged by water or impact. For owners of other 21 V cordless trimmers of matching dimensions. And for service centres and repair shops working on garden equipment: this is the single most frequently replaced part in cordless trimmer repair, with volume pricing available from three units.

Useful during replacement: the M5 hardware kit (bushings, nuts and washers) if the original mounting hardware is worn or missing.

Technical Specifications