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How to fit an Isotronic marten deterrent in a car

Updated: 22 October 2026

The bay already smells of the animal, and you have a 78440 or another Isotronic box ready to fit. How to fit an Isotronic marten deterrent in a car means a wash first, a speaker in open air, and black, brown and grey leads that are not the colours on a Kemo or K&K sheet. A mat over the speaker, a cable on the manifold, or a guessed terminal 15 on a CAN-bus car fails the job before anyone can ask whether the sound worked. This is the sequence, not a ranking, of the listings in the [Isotronic marten deterrent comparison](/hub/pest-control/isotronic-marten-deterrent). We did not fit a unit. A qualifying purchase can earn a commission at no extra cost to you.

The bay already smells of the animal, and you have a 78440 or another Isotronic box ready to fit.

Our top picks

Isotronic Isotronic 78440 12 V car ultrasonic

Best overall

Isotronic Isotronic 78440 12 V car ultrasonic
8.2/10about £25.61
View offer
Isotronic Isotronic 78580 LED ultrasonic dual power

Alternative

Isotronic Isotronic 78580 LED ultrasonic dual power
7.6/10about £32.45
View offer
Isotronic Isotronic LED ultrasonic with vibration sensor

Alternative

Isotronic Isotronic LED ultrasonic with vibration sensor
7.2/10about £31.18
View offer
On this page
  1. 1.Clean the scent marks first
  2. 2.Place and fix the box
  3. 3.Connect model 78440
  4. 4.When a garage does it

Clean the scent marks first

Wash the scent marks in the engine bay and on the ground under the car before you fasten anything. The 78440 instruction treats that wash as part of fitting, because mice and rats follow scent back to a place they already know. Use a cleaner that is safe on paint, rubber and wiring, and let the bay dry. A clean bay still blocks the sound if a mat covers the speaker. Wash first, then look for an open metal surface. If the droppings might be a pine marten, or the space is a loft with bats or a hazel dormouse, stop and read the pine marten deterrent UK law page. The wash does not repair a loom that is already chewed.

Place and fix the box

Fasten the 78440 with the screws or cable ties the instruction allows, and point the speaker into open air. The sheet gives an angle of about 140° and a lead of about 100 cm. Do not stretch that lead. Route it clear of the fan and the exhaust manifold. The instruction says fitting is for authorised specialised staff. A module inside a foam pocket can look tidy while the speaker faces the foam. Battery boxes use screws or cable ties too. Do not bury those speakers. UK reviews on the vibration LED say the cover screws are too small. Do not force them. Model 78580's UK bullets do not state a vibration sensor, even though a separate manual does. Cells versus the car battery is the 12 V or battery page. The downpipe belt, model 84025, does not belong in the bay.
Isotronic Isotronic 78440 12 V car ultrasonic

Testsieger

Isotronic Isotronic 78440 12 V car ultrasonic
8.2/10about £25.61
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Connect model 78440

On the 78440 only, black goes to positive, brown goes to negative, and grey goes to terminal 15, so the module runs with the ignition off. There is no red lead. Do not copy a STOP&GO diagram that ties earth to terminal 15, and do not copy Kemo or K&K colours. On a CAN-bus car the grey lead goes to the fuse of terminal 15. The title's CAN-bus line does not replace that fuse. If the fuse card does not name it, stop. The sheet lists about 5 mA, about 0.6 W, an external fuse of 250 V / 0.2 A, and 12–23 kHz at about 80 dB, with about 15 seconds on and 15 seconds off. Disconnect the module if the car will sit unused. The 5 mA figure does not cancel that sentence. A neat fitting is not an efficacy claim. Who should attempt this module is on the best Isotronic marten deterrent page.

When a garage does it

Hand the car over when the loom is already chewed, when you cannot name the terminal-15 fuse on a CAN-bus car, or when the 12 V battery is not in the bay. A lead of about 100 cm will not reach a boot battery, and extending it is not the instruction. The same stop applies if the animal might be a pine marten, a bat or a hazel dormouse. A battery unit on an undamaged car does not need that handover unless the cables are already damaged or the species question is open. Fitting as the sheet describes is not a result.

Common questions

Where does the 78440 speaker face?
Into open air in the engine bay, at the stated angle of about 140°, not into an insulating mat. A module hidden in foam can still be tied down neatly and still fail this step.
Which colour goes to positive, negative and terminal 15?
Black is positive, brown is negative, and grey is terminal 15. There is no red lead. Kemo, K&K and STOP&GO sheets use other colours. If the fuse card does not show terminal 15, stop.
What changes on a CAN-bus car?
The grey lead goes to the fuse of terminal 15, not to a pin you have guessed. The title's CAN-bus wording does not replace that fuse. If the car's own card does not name it, a garage should make the joint.
Why wash the bay and the parking place first?
Animals return to a place they can still smell, so the instruction puts the wash before the screws. Detergent does not help if you then cover the speaker, and it does not repair chewed wiring.
Can I leave it connected if the car sits for weeks?
No. Disconnect it if the car will sit unused. About 5 mA does not cancel that line, and a cut-out on a battery box is not permission to leave the 78440 joined.
How do I fit a battery unit without burying it?
Use the screws or cable ties the listing allows, and keep the speaker out of foam. Do not force the tiny cover screws on the vibration LED, and do not treat 78580's separate manual as if it were printed on the UK bullets.
When do I stop and pay a garage?
Stop if the loom is chewed, if terminal 15 is unclear, or if the 12 V battery is in the boot. Stop as well if the animal might be a pine marten, a bat or a hazel dormouse. The line about authorised staff is the same caution.

Related pages

Isotronic marten deterrent

Isotronic marten deterrent: 12 V or battery supply

Best Isotronic marten deterrent for a parked UK car

Isotronic marten deterrent buying guide for UK cars

Pine marten deterrent UK law before you fit one

Sources

Public UK sources used for this comparison. Shelf prices, stars and review counts are the amazon.co.uk figures captured for these five listings. Last checked 20 October 2026.

  1. Wildlife and Countryside Act 1981, Schedule 5 (retrieved 20 October 2026)
  2. NatureScot, pine martens (retrieved 20 October 2026)
  3. GOV.UK, hazel dormice (retrieved 20 October 2026)
  4. Bat Conservation Trust, rats and mice where bats are (retrieved 20 October 2026)
  5. ASA, pest repellents (retrieved 20 October 2026)
  6. Rentokil UK, mice repellent myths (retrieved 20 October 2026)
  7. Vincent Wildlife Trust, pine marten (retrieved 20 October 2026)
  8. Isotronic 78440 instruction (retrieved 20 October 2026)