25 September 2026
8 min read
Worthing Auto Locksmith
A fob that works from closer than it used to usually has a fading cell, because range drops long before the buttons stop. Two questions settle the rest. Does the spare do the same, and does it happen everywhere?
Nothing has failed yet, which is the useful part. Range is the first thing a fob loses and the buttons are the last, so there is usually a few months between noticing this and being stood next to a car that will not open.
What counts as normal range
Wider than most people expect, and that is worth knowing before deciding anything has gone wrong.
Remote keyless entry in the UK runs at 433 MHz. Most cars unlock from somewhere between 5 and 20 metres, and some manage 50 metres or more in open air. A small city car and a large estate from the same year can differ by a factor of three, because the number of aerials in the car and where they sit matters more than the fob does.
So there is no single correct distance, which makes the usual advice useless. What matters is not the number, it is whether your number has changed.
Pace it out once and write it down. Walk away from the car pressing the button, count the steps at the point it stops responding, and note it somewhere. That takes a minute and it turns every future comparison into a fact rather than an impression. It is also the only way to find out whether the range really has dropped or whether you simply started parking further away.
Is it the fob or the car?
The first of two questions, and the spare key answers it.
Take the spare out, walk the same distance from the same spot, and press it.
- The spare reaches further. The fault is in the everyday fob. Everything from the battery section down applies
- Both are equally short. The car is the more likely problem, and two fobs do not weaken at the same rate by coincidence
One honest qualifier. A spare that has sat in a drawer for six years has a cell as old as the car, so a spare that performs badly proves less than a spare that performs well. If both are poor and the spare has never been used, put a fresh cell in the spare before drawing any conclusions.
Everywhere, or only in one place?
The second question, and it removes half of this article for whoever it applies to.
Short everywhere means the fob or the car. The distance is the same at home, at work and at the supermarket, and it has been getting worse over weeks.
Short in one place only means interference, and nothing is wrong with either. The fob works normally on your own street and needs two metres in the office car park, or it is fine every morning and poor every evening. That is not a failing fob, it is a radio environment.
The test is free. Try the same fob at the same distance somewhere completely different. If the range comes back, stop looking at the fob entirely and read the interference section instead.
The battery, and what weak means
The commonest cause by a wide margin, and the reason this query exists at all.
A fob runs on a 3 volt lithium coin cell that lasts three to five years in normal use. What catches people out is the order in which things fail. Transmitting across a car park takes more power than transmitting from two metres, so the range shrinks first and the buttons go on working long afterwards. A driver whose doors still unlock reasonably concludes the battery is fine. It is not fine, it is part way through dying, and the shrinking range is the only warning it gives.
Cold brings it forward. A marginal cell that manages twenty metres in September manages five on the first frosty morning, then recovers by lunchtime, which is why this gets dismissed as a one-off. Where a new cell goes in and nothing improves, the after a battery change checks are the next thing to work through.
How you hold it changes range
Two free things change range measurably, and between them almost nothing on the internet mentions either.
Hold it higher. Chest height rather than by your side. A fob held low is transmitting through your own legs and whatever car is parked between you and yours.
Turn it ninety degrees. This one surprises people. The aerial inside a fob radiates in a particular orientation, and the receiver in the car expects to hear it in a particular orientation. When the two do not match, part of the signal is simply lost. Flat in the palm and upright in the fingers are genuinely different, and on the edge of the range that difference decides it.
Touch it to your chin or the side of your head. The old trick, and it does work. Your body is largely water and it conducts, so holding the fob against it effectively enlarges what is radiating. It is worth a couple of metres rather than ten, which is enough when you are just short.
Do not close your fist around it. Here is the part nobody mentions alongside the trick above. Human tissue also absorbs radio energy and pulls the aerial off tune, so a fob buried in a tight grip transmits worse than one held lightly between finger and thumb. Touching it to your head helps. Wrapping your hand round it does the opposite.
Interference around where you park
Where the second question pointed at one location, this is the section. It splits into what you can do nothing about and what you can go and unplug.
Structures and background noise are fixed. Steel reinforced concrete in multi-storey and underground car parks, metal buildings, broadcast and phone masts, overhead power lines and substations, and heavy rain. None of it is your problem to solve, and the answer is to walk closer in those places and stop worrying about it.
Local sources are different, because they are usually within a few metres and usually somebody has plugged them in recently. The reliable culprits are a failing phone charger, dimmable LED lighting, unshielded computer equipment, electronic signage, retail security gates near a parking bay, and motion sensors.
If the range collapsed at home and nothing about the car changed, think about what was plugged in around that time. A cheap charger left in a hall socket is behind a surprising number of these, and unplugging it for an afternoon proves it one way or the other.
One more that catches people out. A second fob pressed against the first in a pocket, or a fob sitting on a wireless charging pad, interferes with itself at close range.
Wear inside the fob itself
Where the cell is new, the spare behaves better and the range is short everywhere, the fob itself is wearing out.
Four things go, and none of them is visible from outside.
- Cracked solder joints, usually from being dropped, which make a connection that works some of the time
- Worn contact pads under the buttons, where the conductive layer has thinned after years of pressing
- Corrosion left behind by a cell that leaked, which spreads quietly across the board
- Water, and this one has a specific cause. Fobs are sealed with a gasket, and a case that has been opened for a battery and not pressed fully shut stops being sealed
Heat matters too. A fob that lives on a dashboard in summer, or in a trouser pocket all day, ages faster than one that does not. Key fob repairs deal with all four without a new fob being needed, because the chip already paired to the car is reused.
When the car is the problem
If both fobs are equally short, look at the car.
The 12 volt battery is first, and nobody suspects it. Below roughly 11.5 volts the receiver and aerial circuits misbehave before the starter does, so the car goes on starting perfectly while the range falls away. Dim interior lights or a radio that resets itself are the supporting signs.
The receiver module is second. Rare, and it produces a car that ignores both fobs from any distance while working fine with the key in the door. Where the car reports a key it cannot find at all rather than simply hearing it late, the key not detected warning is a different fault with its own checks.
One thing worth knowing before assuming anything. Modern cars carry several receiving aerials in different places, which is why range is often noticeably better approaching from one side than the other. That is normal and it is not a fault.
Why a new fob can be worse
This catches out a particular reader, and they are usually the most frustrated person on this page.
A fob was replaced, and the new one works from half the distance the old one did. The obvious conclusion is that the car has developed a problem. Usually it has not.
Three things differ between an original fob and a cheaper replacement, and all three affect range. The aerial layout on the circuit board is not always identical, and small differences in component placement change how well it radiates. The receiver in the car was tuned around the original key, so it hears that design best. And build quality varies, particularly the soldering and the chip itself.
That is not an argument for going to a dealer. It is an argument for asking what is being fitted before it is fitted, because the difference between a good aftermarket fob and a poor one is far larger than the difference between a good aftermarket fob and an original. Fobs supplied and programmed is a question worth asking that way round.
Why this is worth fixing now
There is a real argument for dealing with this while it is still an inconvenience, and it is about timing rather than urgency.
Range is the first thing to go and the buttons are the last. The gap between the two is usually a few months. Right now the car still opens, the fob still works, and there is time to do something about it at a moment that suits you.
The same fob in February is a different situation. Cold weather takes a marginal cell from short to dead in a morning, and a fob that stops working altogether in a car park is an unplanned call-out rather than a booked visit.
The checks themselves are short. The cell is measured under load rather than at rest, because a coin cell reading close to 3 volts with nothing drawing from it still collapses the moment the fob transmits. The fob is checked for output, which separates a power problem from a board problem. The spare goes in, and the car is read for what it has actually been hearing. Remote car key repair covers the outcome where the board rather than the cell has gone.
How to keep the range you have
Five habits keep a fob working from the same distance for years.
Change the cell every two years, not when it fails. It costs very little and it removes the cause behind most of this page before it starts.
Take the weight off the keyring. A heavy bunch swings against the case all day, and the repeated flexing is what cracks solder joints inside.
Keep it out of the sun. A dashboard in August is a hostile place for a circuit board, and heat ages electronics faster than use does.
Do not carry it pressed against a phone. Same pocket is enough to cost a few metres, and a separate pocket costs nothing.
Close the case properly after a battery change. The seal only works when the two halves are pressed fully home all the way round, and a fob that lets water in slowly is a fob whose range fades for reasons nobody connects to the afternoon it was opened. Where it has gone too far for that, what a replacement costs depends far more on the type of fob than on the car.
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