Called back within a day and gave good advice.
Rob and Sue Dempster · Jun 2026 Google
Sunsynk · Datalogger · No LED lights · C9
Sunsynk logger with no lights is usually not the logger
No green LED, no red LED, nothing in the app, and the system has vanished from monitoring. In most cases of a completely dark logger the dongle is fine and the 12V supply feeding it has failed, on a small board inside the inverter. Your solar keeps generating throughout. Start with the two free checks below before anyone charges you for anything.
Free remote diagnostic two free checks first; if it needs a visit, quoted before anyone travels
- Your system keeps generating
- Free checks first
- In warranty? We will say so
Logger dark and the app blank?
Tell us what the logger LEDs and the inverter screen are doing. We can usually tell you from that whether it is the dongle or the supply inside the inverter, before anyone travels and at no charge.
Ask about a dead loggerMonitoring offlineThis company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing. If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.
Andy Thomas · Apr 2026 Trustpilot
Amazing! I was having trouble with a flat GivEnergy battery and solar panels not working. I contacted through WhatsApp and we managed to get it all sorted within a couple of days! Super fast service. I can’t thank you enough for your help when my installer didn’t want to know and GivEnergy has gone in to administration! I know where to go if anything happens again!
Chrissy For · Oct 2026 Google
Givenergy panels and battery had been offline for a couple of months after various changes by Givenergy to their app etc. Ron did a fantastic job of sorting it out - got things up and running almost immediately, followed by some fine tuning to get things fully configured. What a legend - great service, great comms, great result.
Mr Chapman · Aug 2026 Google
Called spoke to Ron. Was very informative and more importantly listen to the issues regarding my system. Was very professional and tackled the problem and had my system back on it's way. Thank you once again Ron
Shawn Carmichael · Aug 2026 Google
Big thanks to Ron. He was incredibly patient and helpful over the phone, taking the time to walk myself and the installer through every troubleshooting step. Through lots of testing he figured out the issue was definitely a hardware issue, which allows us to consider our next steps. Support fees are clear and they operate a “no fix no fee” policy. It is rare to find that kind of honesty combined with dedicated phone support nowadays. I highly recommend Ron, if you need help with your solar system don’t hesitate to give him a call.
Steve M · Jun 2026 Google
What you are seeing
A logger with no lights at all
Not a logger with a red light, and not one that connects and then drops out. This page is about a datalogger showing no green and no red LED whatsoever, with the system gone from the app entirely.
The distinguishing feature is what the inverter itself is doing. Sunsynk's own description of this fault assumes the inverter is fine: the Normal LED is lit and the power flow for grid, load, PV and battery still reads correctly. If that matches your system, nothing is wrong with your generation or your battery. You have lost the reporting, not the machine.
One variant worth knowing about
Some owners report that the same board fault also blanks the inverter's own screen, and in a few cases the RS485 link to a battery or a local monitor, while the inverter carries on running normally underneath. Sunsynk's articles do not mention this, so treat it as a pattern owners describe rather than a manufacturer position. It matters because a dead screen looks like a dead inverter, and it is worth ruling this out before anyone quotes you for a replacement.
Do these first · both free
Sunsynk's own order of checks
Neither of these needs us, and both are published by Sunsynk. Work through them before you pay anyone, including us.
1
Try a different datalogger
Sunsynk's first step is to swap the suspect logger for a new or known-working one. If the replacement lights up, the logger had failed and you are done, though you will then need to unbind the old logger from your plant and add the new one using its serial number and key. If the replacement is also dark, the logger was never the problem, and buying another one will not help. Borrow one if you can rather than buying to test.
2
Have the supply measured at the DB9 socket
The 12V that powers the logger arrives on pins 5 and 9 of the DB9 socket the logger plugs into, and a meter across those two pins settles whether the inverter is still supplying it. Sunsynk scope this one to installers and competent electricians rather than owners, so it is not a step to attempt yourself, but it is quick for anyone qualified and it does not involve opening the inverter.
12V present: the supply is fine, so the fault is the logger itself or your network. No 12V: the supply has failed inside the inverter, which is the fault this page is about.
Where Sunsynk's own guidance ends is worth noting: when there is no voltage on those pins, their troubleshooting article tells you to contact Sunsynk support rather than to start cutting components out. Sunsynk offer support to end users directly, free, and that is a genuine route rather than a formality.
The C9 capacitor
What has actually failed
On the small Wi-Fi card inside the inverter there is a capacitor marked C9, sitting next to the connector labelled P2. It sits across the 12V supply rather than in line with it, which is the detail that explains everything else: when a capacitor in that position fails short, it pulls the rail down to nothing, and the logger receives no power. Sunsynk describe the effect as the failure stopping power reaching the logger.
The published repair is to remove C9 and leave it out. That sounds alarming until you see why it works. Because the part sits across the rail rather than in it, taking out the short restores the supply. Sunsynk are explicit that it is, in their words, "a non-essential component" and that removing it allows the logger to resume operation. It is a genuine hardware failure, but it is not a failure of anything that makes your system generate or store energy.
Why we will not talk you through doing it
Sunsynk's procedure begins by isolating the AC and DC supplies and removing the inverter's front cover. That is not a homeowner job on a hybrid inverter, and this page deliberately does not reproduce the steps. There is also a warranty consequence covered below, and doing it yourself is the fastest way to trigger it. Sunsynk publish the procedure for installers; we have linked their article rather than rewriting it.
It is also not a certainty. Sunsynk are clear that if removing the capacitor does not work, or if there is voltage across it and the logger is still dark, the logger itself is back in the frame. Where the board is confirmed faulty and an owner would rather not have it repaired in place, Sunsynk can supply a replacement board or take the inverter into their service centre.
Two things this page will not tell you, because no source supports them. It will not name the models or production dates affected, because Sunsynk's articles name none and their knowledge base carries no model-scoped version. And it will not tell you how common this is across Sunsynk inverters generally. Sunsynk's "in most instances" wording is about this symptom, meaning that given a dark logger the board is the usual culprit, which is a narrower claim than it first reads.
Read this before you call anyone
If you are in warranty, go to Sunsynk first
Sunsynk's current warranty runs to a cumulative ten years on the inverter. It also excludes cover where repair work on the product is carried out by anyone other than Sunsynk or a Sunsynk certified installer. Read those two together and the conclusion is simple: if your inverter is still covered, letting an independent company open it can cost you the remainder of a decade of cover on a four-figure asset.
So if you are in warranty, your first call is your original installer or Sunsynk, and it should cost you nothing. We would rather tell you that and lose the job than take money for something you were entitled to have done free. If you ring us and that is your situation, that is what you will be told.
Where owners come to us instead is the situation this whole company exists for: the system is out of warranty, or the installer has stopped answering, or Sunsynk have offered a depot repair and being without monitoring for the turnaround is not workable. In those cases Sunsynk authorise this repair on a case-by-case basis, and we obtain that authorisation in writing for your specific inverter before we start. We are an independent repairer with no affiliation to Sunsynk.
What we do and what it costs
Free to find out, from £345 to fix
Free remote check
Tell us what the logger LEDs are doing, what the inverter screen shows, and what happened before it went dark. In most cases we can tell you from that whether you are looking at the logger or the supply inside the inverter. If you can do the DB9 measurement, that usually settles it outright. No charge, and no obligation. If the logger lights up but won't join your WiFi, that isn't remote work: start with our general WiFi checks.
On-site repair · from £345
A fee covering the visit, isolating the inverter on AC and DC, the repair itself, and confirming the logger comes back up and reconnects. No part is fitted, so you are paying for the visit and for someone who has done this before, not for hardware. Quoted and agreed before anyone travels.
Two honest notes on that price. It is a visit, so it sits outside our no-fix-no-fee policy in the same way every on-site job does; the free part is the diagnosis that happens first, and it is genuinely free. And if we arrive and the fault turns out to be something else, you get told what it actually is rather than having the original quote applied to a different problem.
If your installer has gone under and you have been left with a system nobody will look at, that is the most common version of this call and there is a page for exactly that situation.
Related pages
Sunsynk's own articles
Sunsynk datalogger questions
Usually not, and this is the check worth doing before you spend anything. Sunsynk’s own troubleshooting says to try a second, known-good datalogger first. If the replacement also shows no lights, the logger was never the problem: the 12V supply reaching it has failed, and that comes from inside the inverter. A dongle is inexpensive and worth borrowing or trying if you have one, but buying a new one on the strength of a dark logger is the most common wasted purchase on this fault.
Yes. Sunsynk’s own description of this fault assumes it: the inverter’s Normal LED is lit and the power flow for grid, load, PV and battery is still correct. Your panels keep generating and your battery keeps charging and discharging on whatever schedule it already has. What you have lost is visibility and remote control, not generation. Anyone telling you the system is dead has not looked properly.
Three things, and the third is the one people underestimate. You lose monitoring, so the app shows nothing. You lose remote settings changes, because Sunsynk route those through the datalogger, which means tariff and charge windows can only be changed at the inverter’s own screen in person. And you lose the ability to update the inverter firmware at all, because Sunsynk state that the update feature cannot be reached from the inverter control panel. If you are on a time-of-use tariff and your windows need changing, that third point becomes a real cost rather than an inconvenience.
Partly. The one check that is genuinely yours to make is swapping in a different datalogger, and it answers the question most of the time. The electrical test that settles it is a meter across pins 5 and 9 of the DB9 socket the logger plugs into, which shows whether the inverter is still supplying 12V. Sunsynk scope that one to installers and competent electricians rather than owners, so it is not one to attempt yourself even though it needs no cover removed. If you have an electrician you use, it takes them a minute. If 12V is present, the fault is the logger or your network. If it is absent, the supply inside the inverter has failed.
Check before you let anyone touch it, including us. Sunsynk’s current warranty runs to a cumulative ten years, and it excludes cover where repair work is carried out by anyone other than Sunsynk or a Sunsynk certified installer. If your inverter is in warranty, the correct first move is Sunsynk or your original installer, and it should cost you nothing. We will tell you that on the phone rather than take the work. Where an owner does want us to do it, Sunsynk authorise this repair case by case, and we obtain that authorisation in writing for your specific inverter before we start.
The remote diagnostic is free: tell us what the logger and the inverter screen are doing, and we will work out whether this is the board or the dongle at no charge. If it is the board, the repair is on-site, from £345, because the inverter has to be isolated on both AC and DC and opened. No part is fitted, so you are paying for the visit and for someone who has done it before, not for hardware. If we get there and it turns out not to be this fault, we will tell you what it is instead.
Start with the free check, not the repair
Tell us what the logger is doing, what the inverter screen shows, and roughly how old the system is. If this should be a free warranty claim we will tell you that and how to make it. If it is the board and you want us to sort it, we will say what it costs before we go anywhere.
Service notice
We’re busier than ever. Thank you for your patience.
Due to unprecedented demand we’re currently only carrying out on-site work in Yorkshire, and replies are taking up to 7 days. Remote diagnostics continue for the whole UK as normal.
Every message is read and answered, so please don’t send it twice; that only slows the queue.
Ronald Director, Solar Tech Support
On-site: Yorkshire only, for now
Remote: UK-wide, as usual
Remote fix: £125 if we fix it, no charge if we don’t
Replies: within 7 days
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