Key takeaways
- When one pole is dark, look at the fixture. When a whole row is dark, look at the control or the circuit.
- Photocells, time clocks and lighting contactors fail more often than the fixtures they control.
- Underground circuit faults are the slowest to find and the most expensive to fix, so they are worth diagnosing properly before digging.
- When the old heads need repeated lamp and ballast work, an LED retrofit of the pole heads is often the better repair.
Parking lot lighting repair is one of the most common commercial electrical calls in San Antonio. Pole lights sit outdoors year round, take the summer heat and the spring storms, run every night on controls that wear out, and are fed by wiring buried under asphalt where nobody can see it. When the lot goes dark, customers and tenants notice right away, and so does anyone looking for a place to break into a car.
This guide explains how a parking lot lighting system is put together, the usual reasons it fails, and how a good electrician finds the fault without guessing.
How a parking lot lighting system works
Most commercial lots have the same basic parts. A circuit starts at a panel inside a building or at a pedestal outside. It passes through a control that decides when the lights are on, usually a photocell that senses darkness, a time clock, or both. On larger lots the control does not carry the lighting load itself. It switches a lighting contactor, a heavy duty relay that turns the whole circuit on and off. From there the wire runs underground in conduit to each pole, up through the pole base, and to the head at the top.
Each pole usually has a handhole near its base where the circuit wiring connects to the fixture wiring, often with an inline fuse. The head holds the lamp and its driver or ballast. Older lots run metal halide or high pressure sodium heads. Newer ones run LED.
Read the pattern first
The pattern of what is dark says a lot about where the problem is. An experienced electrician starts there, before anyone rents a lift.
- One pole dark: usually the lamp, the ballast or driver, the fuse in the pole base, or the connection in the handhole.
- A whole row or a whole circuit dark: usually the breaker, the contactor, the photocell or time clock, or a fault in the underground run that feeds that row.
- Lights on all day: a failed photocell, a time clock that lost its setting after an outage, or a contactor stuck closed.
- Lights cycling on and off at night: a lamp near the end of its life, a failing ballast, or a photocell that sees light from the fixture itself.
- Lights that work some nights and not others: often moisture in a pole base or a splice that opens up when it is wet.
Controls fail more than fixtures
The photocell, the time clock and the contactor are small, cheap parts that do a lot of work. A photocell faces the sky in full Texas sun every day. A mechanical time clock loses its setting when the power blinks during a storm, and nobody resets it. A contactor closes under load every evening and opens every morning, and its contacts wear and pit over the years.
These are often the first things checked on a dark lot, because they are quick to test and quick to replace. Replacing a mechanical time clock with a digital one that keeps its program through a power loss, or with an astronomical clock that tracks sunset through the seasons, solves a recurring problem on many properties.
Pole base and underground faults
If the controls are good and a whole run is still dark, the problem is usually underground or at a pole base. Water is the common cause. Conduit cracks under parking lot loads, joints separate, and handholes fill with water and debris. A splice that was never made for wet locations slowly corrodes until it opens. Grounds crews, sign installers and other trades sometimes cut through a buried run without knowing it is there. Vehicles knock poles and crack bases.
Finding an underground fault means testing the circuit in sections, pole by pole, to narrow down where the break or the short is. An insulation test shows whether the wire is leaking to ground. A good electrician does that work before recommending any digging or boring, because cutting asphalt in the wrong place costs time and money. Sometimes the fix is a single bad splice in a handhole. Sometimes the run has failed in several places and the honest recommendation is to pull new wire, or to install a new conduit run.
Lift work and safety
Pole heads sit well above the reach of a ladder, so most head work needs a bucket truck or a lift. That has to be planned around the lot's traffic, with the area under the work coned off. Many owners save money by having every dark head handled in one visit instead of paying for the lift several times a year. It also makes sense to check the heads that are still working while the lift is there: a cracked lens, a loose head, or a failing ballast is cheaper to fix now than on the next trip.
A pole that has been hit, or a base that is cracked or rusted through, is a structural problem as well as an electrical one. A leaning pole or a loose head can fall in high wind. If the base or anchor bolts are damaged, the pole should be taken out of service and the circuit made safe until the base is repaired or the pole is replaced. Wall packs on the sides of buildings are easier to reach, but they fail for the same reasons, and they are worth checking in the same visit.
When to repair and when to retrofit with LED
Older metal halide and high pressure sodium heads are expensive to keep running. Lamps fail on a schedule, ballasts fail, and metal halide lamps lose a large share of their light well before they burn out, so a lot can get dimmer for years before anyone files a work order. Replacement lamps and ballasts for older heads are also getting harder to find.
An LED retrofit replaces the old head, or its internals, with an LED fixture designed for the pole. LED heads use less power, last much longer, and direct light down at the lot instead of up into the sky. If the lot already needs a lift for repairs, retrofitting the heads in the same visit is often the better use of the money. The circuit, controls and pole bases still need to be sound, so the repair work and the retrofit go together.
Our LED lighting retrofit service covers how we plan a retrofit for a parking lot or a warehouse, and our lighting installation service covers new fixtures where there were none.
Who to call and what to expect
Parking lot lighting is commercial electrical work, and it should be done by a licensed electrical contractor. In Texas that means a company licensed by TDLR with a licensed master electrician responsible for the work. If the repair includes new circuits, a new pole or a service change, a permit may be needed, and the contractor should pull it.
At Wattsmith, we diagnose the fault, tell you what we found, and give you a written price before we fix it. We can schedule lift work early in the morning or on a slow day so the lot stays open. Property managers responsible for retail centers, office parks and apartment communities often fold site lighting into a scheduled visit so poles are checked before they fail.
Read how that works on our maintenance agreements page. Apartment communities have their own mix of site and common area lighting, covered in multifamily common area electrical. For everything else, see our commercial electrical services.