Showing results for 
Search instead for 
Did you mean: 

My Broadband Doesn't Work!

My Broadband Doesn't Work!

My Broadband Doesn't Work!

The purpose of this blog is to help you diagnose your broadband fault. There is a fault diagnosis flowchart to accompany this, if you wish. I'm quite sure nearly everyone reading that will be familiar with the above phrase, most of you because it's happened to you on occasion and you've needed to call your ISP's helpdesk to find out what's going on, and many of you because you've had someone on the phone to you uttering those words. Either way, our sympathies are with you. Before we go on to do any diagnosis I should explain why home diagnostics are necessary and why we can't just 'push our magic button' and make the service work again.

You can also check our handy guide about what is a good broadband speed?

Quick links:

Testing from the master socket

Sync light OFF or FLASHING

Sync light ON

No Sync fault

Intermittent Sync fault

Authentication fault

Other issue (slow speed, no data transfer)


Whose Fault is it? There's three different parties that could be causing the problem. Firstly, there's you, the End User. By far the majority of broadband faults are caused by issues at the End User's premises, which is why we ask you to test the service beforehand. Sync faults can be caused by anything from electrical interference to incorrectly filtered extension cables and there's always a chance that something has broken. In answer to the cry 'but I haven't changed anything' we have to ask, if you go down to the kitchen to make your morning toast and the toaster doesn't work do you think the same thing? Then there's us - the ISP. If you have slow speeds, are unable to log on to the service or are unable to see any web pages there is a chance that this could be something at the ISP end. It is utterly impossible for the ISP to cause any kind of sync fault whatsoever unless we have ceased the service, e.g. for a house move. Finally there's BT, the owner of the line and by far the majority of the equipment that your data passes through. If there is a fault that remains with the broadband equipment plugged into the master socket and all other line items ('phones, fax machines, dialup modems, sky boxes if you have them) removed, chances are it's BTs responsibility to diagnose and resolve the issue. If it then turns out to be the ISP's fault the ISP will deal with the fees from BT, likewise if we have not advised the End User of the required tests and BT then find the fault to be caused by something in the End User's premises. Basically anything from the BT Master socket inwards (including the internal phone wiring in your house) is regarded by BT - the owners of the line - as your equipment and therefore your responsibility. If a fault is reported to BT and they find that the fault is caused by anything there, such as microfilters, broken phone equipment or old wiring etc, they will close the investigation. At this point they will also issue a charge, via us, of £144 + vat. This is the main reason that we need to know you have tested from the BT master socket with two different broadband modems and nothing else connected to the line at all. Provided that the same fault is still apparent with the broadband equipment in this state, it cannot be caused by anything plugged in to the line at your premises. Also provided the fault is still apparent with alternative hardware you have eliminated that as a possible cause too.

So What's at Fault? Let's start with diagnosing the problem. I've made a flow chart to go with this so you can follow it through and see our own process of fault diagnostics. Okay, first thing is to check the sync light on your modem/router. This might also be labelled Act, Link, DSL, Line, or if you have a Netgear it's “that one that looks like a letter 'i' with a circle around the bottom”. This light tells you if the broadband equipment can detect the signal on the line, and also if it can synchronise with that signal - it has to do this before it can connect in the first place. This light will be doing one of three things - it will be off, on, or flashing. If it is off, the modem or router is unable to detect any broadband signal on the line at all. If it's on, the modem/router can find the broadband signal and is able to synchronise with it, meaning that it should be ready to connect. Finally if it's flashing the signal is there but there's something stopping the modem or router from syncing up and therefore from being able to connect. Let's take these one at a time and work through them. routers Before we start the diagnosis for ANY of these fault types, we must first perform a common check. It is possible that your fault could be caused by something else plugged in to one of the phone sockets in your house. In order to remove this possibility you need to plug the ADSL hardware into the test socket behind the BT master socket front plate: BT nte5 master socket This usually looks like the above, with the front panel split into two rather than being a single piece. Depending on the age of your wiring you may not have a master socket that looks like this; if not then it’s the socket where the phone line enters your premises. BT nte5 master socket - open Once you've removed the two screws the bottom section of the front plate should pull straight out to reveal the above. In this picture you can see the wires connected to the back of the frontplate, these lead to your phone extension sockets. As such once the front plate is removed everything has been disconnected from the line, so plug your broadband equipment into this newly revealed socket. Unfortunately you will need to test two different filters in this situation as it may be that the fault lies with one of those. This is as simple as you can get your wiring and will prove that the issue lies with either BT or possibly your broadband hardware, assuming that the fault is still apparent once you’ve removed everything else. Please don’t use any extension cables to fit the modem/router. This is for two reasons, one is that they are themselves the cause of a lot of faults due to being weak and the other is the possibility of double filtering; that is having a microfilter at both ends of the extension. This will remove the broadband signal from the line as by necessity the end of the extension passes through the phone line half of the filter. This removes all frequencies over 4KHz from the line, and as the broadband operates exclusively in frequencies over 4KHz this is all cut off. Bear in mind that if removing all the other items from the line resolves the issue you will need to plug things back in one by one and check the sync light after each. When the sync light starts to flash or goes off you have found the cause of the issue. Once you’ve done this you’ll need to test the hardware to make sure this isn’t the cause of the issue. The best way to do this is to test an alternative. If you don't have one available to test with, and aren't able to borrow one, then perhaps it's possible for you to test your hardware on another line? If you know someone with broadband ask if you can plug it into their master socket for a short while just to see if it picks up on the service. If it does you've proved the fault to be on your line, not with your hardware. If you do find that it's the ADSL hardware at fault bear in mind that this could well be under guarantee. If we supplied the hardware within the past 12 months then it's down to us to replace it - get in touch at and we'll arrange a replacement. If we didn't supply the hardware then we can at least offer to sell you a replacement model. Please raise us a ticket at the above link. If you don't have hardware to test then we can send out a router that you can test with. Raise a ticket at the above and we will have one sent out to you. Before we continue with the testing, please bear in mind that wherever you have the option to send us a ticket or raise a fault you can also call us on 0845 1400200 or 0114 2965198. Right. On with the testing.

The Sync light is OFF or FLASHING Possibilities: Wiring issue Hardware issue Incomplete broadband order No Sync fault Right, so it appears that there is no DSL signal on the line whatsoever. Let's check the obvious first. Is the modem/router powered up and plugged in to the phone socket? (It should be, after the above paragraph). If not, make sure it is and try again. Okay, so your modem/router is now powered up and plugged into the phone socket via a single microfilter and though the power light is now on the sync light is still off (needless to say if the modem/router won't power up it's faulty and most likely the cause of your broadband problem). Next obvious check, have you only just ordered the service? If it was ordered less than 5 working days ago the chances are that the order hasn't completed yet and that's why there's no service on the line. If you are able to get online elsewhere, you can check on your PlusNet broadband order here. So, you have confirmed that the order is definitely complete. As you have already removed everything from the line apart from the ADSL hardware we need to eliminate that as a possible cause. Please see the paragraph above [bookmark]. Job done! Either you've found that the fault is with your own equipment and know what to do to sort it, or you've proved that it is in fact an issue with the line and should therefore report that fault. Now you've done all the diagnostics it won't take five minutes to complete the form at The Sync Light is ON Possibilities: Misconfigured broadband equipment Hardware issue Intermittent Sync fault Authentication fault No Data Transfer issue This is the more complicated one, given there are several types of fault you can have if the sync light is lit. Firstly we need to know if you can connect to the broadband service at all - this means your equipment reports a successful connection, regardless of whether or not you can view web pages. If you're not sure, the best way of checking is via your ADSL hardware. If you use a modem, the connection status should be reported in the system tray (the collection of icons next to the clock on the taskbar, usually in the bottom right corner of your screen), if not please check your modem's manual. If you use a router it should be displayed in the router's configuration pages, usually accessed at one of the following addresses: http://voyager.home (if you have a BT voyager router) (1800 HGW) If none of the above take you to your router's configuration page (or a password prompt) please consult the manual that came with your router to find out how to access this information. If your ADSL hardware is not reporting a successful connection then it is either an intermittent connection fault or an authentication issue. If your broadband does work sometimes then it's an intermittent sync fault. If you find yourself unable to connect at all (or you get a rejected username/password error when attempting to connect) then you have an authentication fault. We'll start by checking for an intermittent sync issue. Start by testing with just the ADSL hardware from the master socket as described above. If the connection still drops then you may well have a line fault but we still need to eliminate your hardware, as above. If the intermittent issue is still apparent you’ll need to report it as a fault via the tool at - filling this in will ensure we have all the relevant information regarding your issue. Authentication faults are issues with your broadband username and password, either with them not being accepted due to being specified incorrectly, a fault with our own authentication servers or a fault with some of the equipment somewhere in between. Bear in mind that intermittent faults can look a lot like authentication issues - if the sync drops are very short your sync light might not even flicker, and chances are what's actually happening is that the connection is dropping during the authentication process so your username and password are being rejected. If you're sure it definitely isn't an intermittent fault after checking your connection logs as per the above then there are, of course, tests that we need doing to prove a line fault. Firstly plug the router or modem into the master socket and unplug everything else from the phone line as per the above. If the fault is still apparent then there are a couple of test usernames that will help to narrow down where the fault may lie. Before you test these make a note of the username that is currently specified in your connection hardware, particularly the bit after the @ sign. This is the connection realm and needs to be present - if it's missing that is probably why you are unable to connect. The first username is bt_test@startup_domain with a password of test. This username should work on any line and will create a connection to the equipment in your local phone exchange, which will not allow connections to any pages other than ( if the previous link does not work). If neither of these works it doesn't necessarily mean that the username has failed, please confirm if the connection is active by checking either the modem software or the router's configuration pages. If that username did not work then the issue lies with the exchange equipment and needs to be tested and reported to BT - please raise this to us via the tool at in order that we can arrange this for you. If the username did work then we need to try another. This is bt_test_user@[realm] where [realm] is the connection realm for your ISP - these are as follows:

ISP Connection Realm(s)
PlusNet (some customers on legacy accounts may be using or
Force 9
Free Online
Metronet or*

*You should be able to use either realm, please test with both. Also please note that the first realm is (dee-ess-el-two dot net) and NOT (dee-ess twelve dot net). This username should connect you to our servers though again the only page you will be able to view is the BT digital demo page (at or If you cannot view this page it does not necessarily mean that the username has not worked, please confirm if the connection is active by checking either the modem software or the router's configuration pages. If the connection is not active then as per the previous test login this is an issue with either the exchange equipment or the link between the exchange to our own servers. This needs testing and raising to BT and as per usual should be reported to us via If the connection is active then we need you to test your own login once again. This is always in the format of [username]@[realm] and will not work if the realm is missing. Even if your username was in correctly before the previous tests, connecting with these usernames forces some of the exchange equipment to reset and may have resolved your fault. If this doesn't work where the other two usernames have, it may well be that there is an issue with our own authentication platform. This should be reported to us in the same way as all other faults. If you're STILL here, then it's not any kind of issue with making and keeping a connection to the internet, so there's some kind of problem with getting the data to you. That might be that it's coming down very slowly or isn't coming down at all. If it isn't coming down at all then there could be a number of possibilities. Some of these may seem daft possibilities but are all faults I have seen during this job. Firstly, do you have an incorrect IP address set in your ADSL hardware? If you're assigned a different IP address to the one specified you won't get any data transfer at all. Change your settings to have your IP address automatically assigned and reboot the ADSL hardware in order to resolve this issue. If not that, have you either lent or sold old equipment to somebody else? If so it might be that this is still configured with your own connection details. This means that the current user is connecting to your own account rather than theirs and as such will prevent you from gaining a working connection. This also holds true if you have given someone your login details to use for a dialup connection. Changing your password via the portal ( is the quickest and easiest way to stop this from happening. Have you recently updated your firewall and/or antivirus software? In some very rare cases these upgrades can be installed incorrectly leading to your internet connection being blocked. The best way to resolve this is to disconnect from the internet (preferably by physically removing the cable) and uninstall the software. Then reboot the PC, do NOT reconnect to the internet at this point but reinstall the application. Once this is installed please reconnect to the internet and before doing anything else ensure that the program is fully updated. Once that is done reboot once more and your problem should be resolved. If it's not that then we need to dial test using your account details to make sure this isn't an issue with the PlusNet network. If you raise us a ticket ( or a DATA TRANSFER fault ( we'll get in touch and arrange a convenient time when you can disconnect and let us connect as you to test your connection. Once we've done that we'll call you again whether this is reported to BT or if further testing is required. If you have a slow speed issue James has written an excellent article on this that I couldn't possibly expand on. You can find this here - James's excellent speed faults blog. The only thing I will say is that you should check your usage via the members centre as it may be that you have exceeded your monthly bandwidth allowance and have had your connection slowed as a result. Well I hope that this has helped, please comment if there's anything else you'd like explaining, adding or clarifying.


0 Thanks
Community Veteran
Something I am not clear about here. When I removed the faceplate there were only 3 wires connected.. I removed one of these (the bell wire) and this more than doubled my connection speed. So what is the 4th wire for which is shown in the picture ? Just curious
According to the page at (apologies for long link) the white wire with orange bands does not actually have a specific function but is usually connected for neatness.
The 4th cable (pin 4) is used to balance the line. Telephone sockets some with 6 pins, formed of 3 twisted pairs. Pins 2 & 5 form the A & B legs used for phone/broadband and use one twisted pair, and legacy setups use pin 3 for the bell wire. To prevent imbalance, it's best to connect pin 4 for the second of the pair on pin 3.
i'm exhausted. one small "q". am on dial-up and wish to change to op 1. if I sign on to 12 mths will I be billed for anything other than the pp and the mthly fee. thanks firefly2
sorri > think am in wrong sctn. firefly2.
you have done a great job with the info. can I go now Huh firefly2
my mouse battery is low. need to go now thanks cus . firefly2
Hi guys. Your flow chart is a really great tool and will come in handy if my broadband fails. I did, however, notice a typo in one of the boxes... Please raise a SLOW SPEED fault at or call us on 0845 1400200; though it may be that nothing can be done, we will try our utmost to improve the connection speed for you. I think 'faults' should have a 'u' in it Smiley
The only thing I would add concerns the part of the diagnosis where you ask the condition of the sync light on the router. Not all routers conform to your "model" - certainly my Linksys does not. The very few times I've had to go through this routine when reporting a BB fault, I've interpreted the Linksys indications and answered the questions to fit "your" model. I'm not sure how many different indications there are with other routers, but the Linksys is popular and it might be worth adding (certainly when going through the routine on the portal) the indications for other routers. On the few occasions to which I refer, my connection returned almost immediately in most cases (as if doing the tests had reset the connection).
Matt I was looking at your fault gudie with interest as my dad has an intermittency of connection, but not of sync, I believe. I say this because he has a Netgear dg834 version 5 which, unlike the previous four versions, has an LED with a chain symbol on it labelled "DSL" and the "i" LED labelled "Internet". So when you say this in your guide "... this might also be labelled Act, Link, DSL, Line, or if you have a Netgear it’s “that one that looks like a letter ‘i’ with a circle around the bottom”." which one is which? Id the chain the DSL/Link LED or is it the "i"? It makes it difficult to fault-find and answer questions on the BB troubleshooter. Please update your (very interesting) guide and advise me of the answer! Thanks, Geoff Bolden
can you tell me why after booking my holiday,my confirmation is not coming through on the e mails they keep sending... I have gone over my e mail address & they have it correctly.. So whats happening to them ?