Most car key remotes that stop working need a £5 to £10 battery, not a new key. If a fresh battery does not bring the remote back, the fault is usually worn buttons, a damaged case or contacts, a lost pairing with the car, or a problem in the car itself. Each one has a different fix and a very different cost. This guide shows you how to tell them apart in a few minutes. It also covers what you can safely do yourself, and when it is quicker to have a mobile locksmith come to you in Essex or Hertfordshire.
TL;DR
- Start with the battery. Replacement remote batteries cost between £5 and £10, and it is the most common cause of a dead remote.
- Try your spare key. If the spare works, the original remote is the problem. If both fail, look at the car, interference or pairing.
- A fob that still fails after a new battery may need pairing with the car, which a locksmith with programming equipment can do on site.
- A worn button, cracked shell or a lost key can often be sorted at your door, without a tow or a dealership visit.
- A new fob from a main dealer can cost from £250 to well over £1,000, so a proper diagnosis first is worth it.
Table of Contents
- Is it really the remote? Five checks before you pay for anything
- What the symptoms usually point to
- How to replace the battery safely
- When the battery is fine: button, case and board faults
- When the remote needs pairing, not repair
- Repair, re-pair or replace: how to decide
- What does remote key repair cost?
- Our perspective: why we repair on site, and when we say don't
- Vans, spares and lost keys
- Getting help in Essex and Hertfordshire
- FAQ
- Sources
Is it really the remote? Five checks before you pay for anything
Before you open the fob or book anyone, spend five minutes on these checks. They cost nothing and they separate a remote fault from a vehicle fault.
- Try the spare key. This is the quickest test. If the spare locks and unlocks the car, the car is fine and your main remote is the problem. If neither key works, the cause is more likely the car's battery, the receiver, interference or a locking fault.
- Stand closer and move away from interference. The AA notes that radio interference can sometimes stop a remote from unlocking the car, particularly on older cars. Car parks near transmitters, busy petrol stations and some industrial estates are common culprits. Try again a few streets away.
- Note which functions fail. If lock works but unlock does not, or one button is dead while the rest work, the problem is probably the button, not the battery. If everything is weak or works only from a metre away, think battery.
- Read the dashboard. Some cars show a low key battery message. Volvo, for example, says a reduced operating range and a “Car key battery low” message indicate that replacement may be needed.
- Check the car's own battery. A weak vehicle battery can make central locking and key detection behave oddly. Renault's owner guidance lists a discharged vehicle battery, interference and desynchronisation among the reasons a remote will not lock or unlock.
If you are locked out while you work through this, the metal emergency blade hidden in most fobs will usually open the driver's door. The AA says cars with remote central locking should have a bypass using the normal key that unlocks the doors without setting off the alarm, and your handbook explains how it works.
What the symptoms usually point to
This table is a practical starting point, not a diagnosis. It reflects how remote faults commonly show up and which repair they usually lead to.
| What you notice | Most likely cause | Usual next step |
|---|---|---|
| Short range, intermittent response, low key battery warning | Flat or weak coin cell | Replace the battery |
| One button dead, others fine | Worn rubber pad or microswitch | Button repair or new shell and switch |
| Buttons need hard pressing, or feel loose | Worn pad, loose board | Repair or replace the case |
| Cracked shell, battery rattles, intermittent contact | Damaged case or battery contacts | Replace the case, check contacts |
| Fob dropped in water or washed | Corrosion on the board | Clean and test, replace if corroded |
| Works after a new battery, then stops again | Poor contact or tired battery | Check contacts and battery type |
| New battery fitted, nothing works | Lost pairing with the car | Re-pair or reprogram the remote |
| Spare fails too | Vehicle battery, receiver, locking system or interference | Vehicle diagnosis, not a new remote |
That last row matters. If the spare key fails as well, spending money on a new remote will not fix anything.
How to replace the battery safely
This is the one repair that is genuinely worth doing yourself.
- Find the opening. The RAC says you remove the small screws or use the fob's release button to open the housing. Many fobs have a small slot where a coin or flat blade can open the shell. Work gently, because the plastic clips snap easily.
- Check the battery number. It is printed on the old cell. Ford UK says battery requirements vary by vehicle and model year, so check the owner's manual or the marking on the existing battery rather than guessing. Many fobs use a CR2032, and Volvo's XC60 instructions specify a CR2032 3 V cell, but others use different sizes.
- Fit it the right way round. Note which side faces up before you remove the old one. Avoid touching the flat faces of the new cell and the contacts with your fingers, as Volvo advises.
- Close and test. Snap the housing shut, refit any screws and test from a short distance, then from further away.
Two cautions. Volvo's guidance covers safe handling of damaged or leaking cells, so do not use a battery that looks swollen or corroded, and keep loose coin cells away from children. And if the fob still fails, the RAC suggests you verify the battery type, orientation and contact with the metal terminals before assuming something worse.
Good news on one common worry: Ford says that replacing the battery does not erase the programmed key. You should not lose your pairing just by changing the cell, though it adds that if the remote still fails afterwards it may need pairing.
When the battery is fine: button, case and board faults
If you have a good battery and a dead or fussy button, the wear is usually physical. Remotes live in pockets, bags and cup holders, and the rubber pad under each button wears through. The tiny switch on the circuit board behind it can also fail. Solder joints crack after drops, and a cracked shell lets in moisture.
What can be repaired depends on the key:
- Worn buttons or pad: often fixed by moving the electronics into a fresh case with new pads.
- Cracked or broken shell: a case swap, keeping the original board and transponder chip. We cover this in more detail in our guide to on-site car key case replacement.
- Damaged or corroded board: sometimes repairable, but often more sensible to replace the remote.
- Broken blade or worn key cut: cutting a new blade is a separate job from the electronics.
A warning on cheap postal repair services: they can work well for a simple button fault, but you will be without your key for days, and if it is your only key, you have no way to drive meanwhile. If you have no spare, a repair that goes wrong can turn into an all keys lost situation.
When the remote needs pairing, not repair
Sometimes the remote is physically perfect but the car no longer recognises it. That can follow a battery change on some models, a flat vehicle battery, a new vehicle battery or a replaced control unit. Renault's guidance refers to desynchronisation and the model-specific synchronisation procedure, which is a useful reminder: there is no universal reset sequence. Some cars let you re-sync with an ignition sequence, and others need diagnostic equipment to pair the remote.
That is where programming comes in. Our key programming service pairs remotes and transponder keys to your vehicle at your location. It is also the route if you have bought a replacement shell or remote and need it to talk to the car. If the car does not start with the key, as opposed to only not locking, read our checks for a transponder key that is not working.
Keyless cars add another layer. If your smart key is not detected, the fault could be the key battery, interference or the car, and our smart key not detected checklist walks through it. For wider fault-finding on proximity systems, see our keyless entry triage guide.
Repair, re-pair or replace: how to decide
| Situation | Best route |
|---|---|
| Weak signal, battery old | Replace the battery |
| Worn buttons, cracked shell, key otherwise sound | Repair or re-case |
| Remote fine, car ignores it | Reprogram or re-pair |
| Key lost, snapped or water-damaged beyond repair | Replace |
| Both keys fail | Check the vehicle first |
| Lost key and want it disabled | Replace and delete the lost key |
A useful rule: repair makes sense when the board and chip are healthy and only the case, pads or contacts are worn. Replacement makes sense when the key is lost, badly damaged or when the repair would cost nearly as much as a new remote. Replacement is also the safer choice when a key has been stolen, because the old key can be deleted from the car so it no longer works.
What does remote key repair cost?
Costs vary a lot by make, key type and who does the work. These are the figures we can point to with sources:
| Item | Cost | Source |
|---|---|---|
| Replacement key fob battery | £5 to £10 (December 2025) | RAC |
| New key fob, typical range | £250 to well over £1,000 | RAC |
| Insurance key cover limits | Typically £100 to £2,500 (April 2026) | Which? |
| AA Protect Plus, electrical failure of remote fobs or cards | Up to £200 including VAT (November 2025) | AA product document |
Our own published prices, as listed on our site: a standard key from £120, a remote key from £150, and key programming from £120. Our emergency callout fee starts from £120. Repairs to fobs and replacement of key fobs are priced to the vehicle, so we quote after you tell us the make, model and year. See our Ford remote key and fob page for an example of the information we need.
Before paying out of pocket, check two things. First, your car insurance might include key cover, and Which? reports that limits typically run from £100 to £2,500 (see the table above), so read the policy wording and the excess. Second, check any warranty or breakdown product, because the AA's Protect Plus document lists electrical failure of remote fobs or cards, up to a limit.
Our perspective: why we repair on site, and when we say don't
We are a mobile locksmith, so we see the whole range of remote problems, from a £5 battery to a car that has lost every key. Our vans carry diagnostic tools so that most of the work can be done at your house, workplace or roadside rather than at a dealership. Our technicians are licensed, insured and SERMI-certified, and that matters for modern security systems.
Our honest advice follows a pattern. Change the battery first, because it is the likely cause and it costs almost nothing. Test with the spare before anyone touches the car. If you are down to one working key, treat that as the real problem: get a spare made while the original still works, because copying a working key is far simpler and cheaper than creating one from scratch after the last key is lost. If a repair will not hold, for example a board with corrosion damage, we would rather tell you to replace than sell you a fix that fails again in a month.
We also tell people when the key is not the culprit. If the spare is dead too, the cause is usually in the car, and a new remote will not help. For ignition-related faults, our ignition barrel repair guide explains what that involves.
— James
Vans, spares and lost keys
Van owners feel a dead remote harder than most, because a van that cannot be locked or started costs a working day. If your van is on the road for a business, a mobile visit saves the trip to a dealer and the wait for a recovery vehicle. We handle van key replacement as well as cars, so mention it when you call.
If the remote is not just broken but gone, see our guides on lost smart keys and whether a locksmith can make a car key. If you are locked out right now, our car lockout service opens vehicles without damage in most cases.
Getting help in Essex and Hertfordshire
We come to you across Essex and Hertfordshire, including Harlow, Chelmsford, Brentwood, Billericay, Epping, Loughton, Ongar, Great Dunmow, Braintree, Stansted, Bishop's Stortford, Sawbridgeworth and Ware. Most jobs are completed on site within 30 to 60 minutes.
To get a quick and accurate answer, have these ready when you call:
- Make, model and year of the vehicle, and the registration if you have it
- What happens when you press the buttons, and which ones fail
- Whether you have a working spare
- What you have already tried, including whether the battery was changed
- Your location, and whether the car is currently locked or immobilised
For a remote that needs repair, programming or replacement, see our full list of key services or contact us through the site for a quote.
FAQ
Can a car key remote be repaired, or do I need a new one?
Often it can be repaired, as long as the circuit board and transponder chip are healthy. Worn buttons, cracked shells and loose battery contacts are common repairable faults. If the key is lost, water-damaged beyond repair or the repair costs nearly as much as a new remote, replacement is the better route.
Why has my key fob stopped working after a battery change?
Check the battery type, which way round it sits and that it touches the metal terminals, as the RAC advises. Ford says changing the battery does not erase the programmed key, but if the remote still fails it may need pairing with the car. The pairing method differs between makes and models.
How much does a key fob battery cost?
The RAC puts replacement remote batteries at between £5 and £10 as of December 2025. Fitting one yourself takes a couple of minutes on most fobs. Always check the battery number in your handbook or on the old cell first.
What if both my keys stop working?
When the spare fails as well, the fault is probably not the remotes. Look at the car's battery, the receiver, interference and the locking system before paying for a new key. A locksmith or auto electrician can test this on site.
Does insurance cover a broken key remote?
Some policies include key cover, and Which? reports limits typically ranging from £100 to £2,500. Warranty products can also help: the AA's Protect Plus covers electrical failure of remote fobs or cards up to £200 including VAT. Check your policy for the excess and for whether a lost key is treated differently from a faulty one.
Sources
- Key fob not working? Here's what to do, RAC Drive
- What to do if you've lost your car keys, The AA
- How to replace the Ford key fob battery, Ford UK
- Replacing the battery in the remote control key, Volvo Cars UK
- Operating faults, Renault user manual
- The car insurance add-ons worth paying for, Which?
- AA Protect Plus insurance product information document