Quick answer: The most common reason a car key fob stops working is a flat battery — an easy, cheap fix you can often do yourself. If a new battery doesn’t solve it, the cause is usually water damage, worn buttons, a fault inside the fob, or a lost connection to your car that needs reprogramming. A mobile auto locksmith can diagnose, repair, reprogram or replace the fob on the spot, usually for far less than a main dealer.
There’s never a good time for your car key fob to stop working. One day it unlocks the car from across the car park, the next you’re stood at the door pressing the button and nothing happens. Before you panic — or pay a dealership a small fortune — it’s worth understanding what’s actually gone wrong, because in many cases the fix is quick and inexpensive.
This guide walks through the common causes, what you can safely try yourself, and when it’s time to call a professional here in Norwich, Norfolk and across East Anglia.
First: Is It the Fob, or the Car?
A quick way to narrow it down. If you have a spare key, try it. If the spare works perfectly, the problem is your original fob. If neither fob works, the issue may be with the car (such as the receiver or a battery/electrical fault), not the key. If you’ve only ever had one key, this is also a timely reminder of why a spare matters — something we cover in our guide to what happens when you’ve lost your car keys with no spare.
Common Causes — and the Fix for Each
| Symptom | Likely Cause | The Fix |
|---|---|---|
| Buttons do nothing, no light | Flat fob battery | Replace the battery (often DIY) |
| Weak range, works up close only | Dying battery or worn transmitter | New battery, then reprogram if needed |
| One button works, others don’t | Worn or cracked button contacts | Fob repair or replacement |
| Stopped after getting wet | Water/corrosion damage | Professional repair or replacement |
| Stopped after a battery change | Fob needs re-syncing | Reprogramming to the car |
| Key turns/starts but remote dead | Remote module fault | Repair, replace or reprogram |
What You Can Try Yourself (Safely)
- Replace the battery first. This solves the majority of cases. Most fobs use a cheap coin-cell battery (often a CR2032), available for a couple of pounds. Pop the fob open carefully, note the battery type, and swap it like for like.
- Check you’ve fitted it correctly. A surprising number of “it still doesn’t work” calls come down to the new battery being in the wrong way round or not seated fully.
- Try the manual key blade. Most fobs hide a physical key inside to unlock the door manually — useful to get you in while you sort the remote.
- Stand closer and test each button. This helps you tell a range problem (battery) from a dead button (contacts).
If a fresh, correctly fitted battery brings it back to life — great. If it doesn’t, the cause is deeper, and that’s where a professional comes in.
When to Call a Professional
Call a mobile auto locksmith if:
- A new battery hasn’t fixed it.
- The fob got wet, was dropped, or has cracked buttons.
- The remote stopped working after a battery change and now needs re-syncing.
- The key starts the car but the remote functions are dead.
- You’re not confident opening the fob without damaging it.
These jobs need the right tools and, in many cases, reprogramming the fob to your car’s immobiliser. A good locksmith can do this at your home, work or roadside — no dealership trip, no towing. You can see how on-site car key programming works, and if the fob is beyond repair, car key replacement gets you a brand-new, programmed remote.
Why “After a Battery Change” Is So Common
Here’s one that catches people out: the fob worked fine, you changed the battery, and now it won’t connect. On many vehicles, removing the battery causes the remote to lose its sync with the car. The key blade and start function still work, but the buttons go quiet. The fix isn’t a new fob at all — it just needs reprogramming back to the vehicle, which takes a locksmith only a few minutes.
Repair, Reprogram, or Replace — Which Will You Need?
- Reprogram if the fob is physically fine but has lost its connection (common after a battery change).
- Repair if it’s a worn button or minor internal fault and the fob is otherwise sound.
- Replace if it’s water-damaged, cracked, or the internals have failed.
We’ll always tell you honestly which one you need rather than defaulting to the most expensive option — and every replacement key we supply comes with a 1-year warranty.
Fob still not working? Autowagon comes to you across Norwich and the wider region with fully equipped mobile vans — on-site diagnosis, repair, reprogramming and replacement for around 90% of makes and models. Call 07395 328717 or request a quote.
Serving Drivers Across Norfolk, Suffolk & Cambridgeshire
Wherever you are, we can help — see our coverage across Norfolk, Suffolk and Cambridgeshire. And while you’re sorting the fob, it’s a good moment to think about protecting the car itself — our guide to keyless car theft protection explains how to keep modern vehicles safe.
Frequently Asked Questions
Why has my car key fob suddenly stopped working?
The most common reason is a flat battery, which is cheap and often easy to replace yourself. If a new battery doesn’t help, it’s usually water damage, worn buttons, an internal fault, or a lost connection to the car that needs reprogramming.
My key fob stopped working after I changed the battery — why?
On many cars, taking the battery out causes the fob to lose its sync with the vehicle. The key may still start the car, but the buttons won’t respond. It usually just needs reprogramming, which a locksmith can do in minutes.
Can a key fob be repaired, or do I need a new one?
Often it can be repaired — worn buttons and minor faults are fixable, and a fob that’s simply out of sync only needs reprogramming. Replacement is only necessary when the fob is water-damaged, cracked, or its internals have failed.
How much does it cost to fix a car key fob?
A battery is just a couple of pounds. Repair, reprogramming or replacement costs vary by make and model, so the best approach is a quick quote — we’ll confirm the price before any work starts.
Do you come to me in Norwich?
Yes — we’re a mobile service covering Norwich, Great Yarmouth, Ipswich, Cambridge and the wider Norfolk, Suffolk and Cambridgeshire area. Call 07395 328717 and we’ll come to your car.