NBN dropouts when it's windy or raining

The job

A customer in Loftus was on fibre to the curb, and the internet dropped out in bad weather. When the wind picked up or the rain set in, the connection slowed, failed, and some time later came back by itself. On a calm, dry day it was fine.

That pattern rules out a lot. WiFi does not care about the weather. A modem does not know it is windy. A fault that keeps time with the weather is in a cable or a joint that is outdoors, and that is where finding a dropout that comes and goes starts.

Watch: NBN FTTC Droping Out When Windy Or Raining Old Aerial Lead In Cable

What we checked

1. 1

   The wiring inside

   The old phone sockets had already been taken off the line when the NBN was connected, so there was no bridge tap. Only one internal cable was in use: a white cable from where the lead-in arrived to the socket in the office.

2. 2

   The internal cable, tested alone

   We disconnected that cable from the lead-in and ran an insulation resistance test on its pairs. The readings were well within specification. The cable inside the house was sound.

3. 3

   What was left

   With the internal cabling cleared, the only copper left in the path was the lead-in itself: an old single-pair overhead cable from the street.

What we found

The lead-in was an old type of aerial cable. Cable of that age and kind is known for developing hairline fractures in the copper inside the insulation. In still weather the two sides of the fracture touch and the line works. When the wind moves the cable they part. When rain gets into the cracked insulation, the signal leaks.

Everything on the customer’s side had tested clean, and the symptom matched the lead-in exactly. So the finding was that the fault was in the lead-in cable, and that it needed to be tested by the network’s own technician and, most likely, replaced.

What's the weather doing?

Calm and dry Wind Rain

Swipe the picture sideways to follow the lead-in to the house.

Street pole Unit in the street Old overhead lead-in Tested clean NBN box Hairline fracture Cracked insulation Signal from the street Power from the box

In still weather the two sides of the fracture touch and the line works. The signal reaches the NBN box, and the box sends power back up the same lead-in to the unit in the street.

When the wind moves the cable, the two sides of the hairline fracture part. The signal stops there, and so does the power to the unit in the street, so the box drops out and has to start again.

When rain gets into the cracked insulation, the signal leaks at the same spot. The connection slows, fails, and comes back some time later by itself.

What happened next

We gave the customer the test results and the finding to take back to their provider, with the advice to ask for the lead-in to be tested and replaced. The value of the visit was the evidence: the home’s wiring had been measured and cleared, so the fault could no longer be put down to “internal wiring”. That written finding is what an independent NBN technician leaves you with, and it is the answer when you are told the fault is in your wiring and it is not.

Why wind and rain cause dropouts

• Overhead cable moves. Every gust flexes it, at the pole, at the house and where it rubs on a tree. Old copper work-hardens and cracks.
• Insulation ages. Years of sun make it brittle. Once it cracks, water gets to the copper.
• Joints are the weak point. Where the lead-in joins the street cable or the house wiring, a poor seal lets water in.
• Fibre to the curb is sensitive. The NBN box inside sends power up that same lead-in to the unit in the street. A cable that leaks or opens up interrupts the power as well as the signal, so the box drops out and has to start again.

If your service does the same

Copy this and keep it for two or three weeks

Date	Time	Weather	What the NBN box lights did

• Report each dropout to your provider and keep the reference numbers.
• Tell them plainly that it follows the weather. That points a technician at the lead-in instead of the modem.
• If you are told the fault is in your home’s wiring, the wiring can be tested by itself, the way it was on this job, and an internet technician can run that test for you. If it tests clean, you have your answer in writing.
• Where the old lead-in turns out to be on your side of the boundary, a new overhead span on a sound fixing is cabling work, and we quote it.

There is more on the causes in does weather affect your internet, and on the connection type in what fibre to the curb is. If the dropouts do not follow the weather, start with why an internet connection is unstable or the common causes of NBN dropping out.