Garage Has No Power: Causes, Checks & Fixes

Do not open wet, damaged or energised outdoor electrical equipment

Water, damaged seals and outdoor cable faults can create serious shock risk. Leave affected circuits isolated and use a registered electrician for fixed outdoor wiring, submains and wet accessories.

MOST LIKELY CAUSES

Start with these

House-side supply tripped The garage feed may originate at the main consumer unit.

Garage RCD or breaker operated One local fault can disconnect the whole outbuilding.

Submain cable fault Damage, loose glands or poor connections can interrupt supply.

Faulty garage appliance Freezers, chargers, tools and heaters may trip protection.

◫ Symptom variations Match the exact behaviour before testing. ⌄

Whole garage is dead
Only sockets or lights are dead
Garage RCD will not reset
House RCD trips when garage is enabled
Power failed after building or driveway work

✓ Quick checks Safe external checks only. ⌄

Check the house consumer unit and any local outdoor board or RCD.
Disconnect portable outdoor appliances and extension leads.
Check indoor fused spurs, switches and isolators supplying the area.
Look for rain damage, condensation, cracked covers and loose cable entries.
Attempt one controlled reset only if all equipment is dry and undamaged.

If operation returns: reconnect loads one at a time and monitor the circuit.

If the fault remains: leave the outdoor circuit isolated and arrange testing.

1 Fix 1 — Check main and garage boards Follow this check without opening live or wet electrical equipment. ⌄

Process

Inspect all relevant front-panel devices.

Success looks like: The supply returns and remains on.

Failure means: If protection trips again, isolate the garage.

2 Fix 2 — Disconnect garage appliances Follow this check without opening live or wet electrical equipment. ⌄

Process

Unplug portable loads before one controlled reset.

Success looks like: The garage supply remains stable.

Failure means: One connected item is likely faulty.

3 Fix 3 — Check switches and fused supplies Follow this check without opening live or wet electrical equipment. ⌄

Process

Look for indoor or garage isolators and FCUs.

Success looks like: An upstream control restores power.

Failure means: If not, the submain needs testing.

⌁ Common causes explained Why outdoor electrical faults develop. ⌄

A garage may lose power because of a tripped house-side device, local consumer-unit fault, switched or fused supply, damaged submain cable, overloaded circuit or faulty connected equipment.

Outdoor circuits face rain, condensation, temperature changes, ground movement and mechanical damage. A fault that disappears in dry weather is still a real insulation or sealing problem.

⌘ Advanced diagnostics Technician-level testing for a competent electrician. ⌄

Test submain continuity and insulation resistance.
Inspect local distribution board and terminations.
Check RCD/RCBO operation.
Verify earthing and bonding arrangements.
Measure load current and voltage drop.

▣ Parts that may need replacing Common components linked to this fault. ⌄

Garage consumer unit
RCD or RCBO
Submain cable
Isolator or fused spur
Cable gland
Faulty appliance

! When to call an electrician Conditions that should end DIY troubleshooting. ⌄

There is water inside a socket, fitting, board or junction.
The RCD or breaker repeatedly operates.
A shed or garage submain is involved.
Cable damage, digging or impact is suspected.
The accessory is cracked, burnt, corroded or pulling away.
The fault remains with portable equipment disconnected.

? Frequently asked questions Common questions about outdoor electrical faults. ⌄

Can I use an outdoor socket after it dries?

Not until the cause of water entry has been repaired and the circuit tested.

Why does the fault happen only in rain?

Moisture lowers insulation resistance and exposes failed seals, joints or cable damage.

Can one outdoor appliance trip the whole house?

Yes. One faulty outdoor item can trip an RCD protecting several indoor circuits.