Are you having trouble with a faulty Sime boiler?
Having a faulty boiler is an annoyance at the best of times, especially when you don’t know how serious the problem actually is and whether or not you need to call an engineer.
This blog post details some of the most common faults you can experience with a Sime boiler, to help you diagnose the problem and understand what the solution entails – there may even be a couple of easy fixes you can try yourself.
NOTE: If you’re ever in any doubt, or the problem isn’t an easy fix like adjusting boiler pressure or unblocking a frozen condensate pipe, DO NOT try to fix the problem yourself; always call a Gas Safe registered engineer.
About Sime boilers
The company Sime had its beginnings as an Italian manufacturer of heat exchangers, before starting to manufacturer its own gas boilers back in 1973. Sime had some very popular combi boilers which it sold through merchants from the early ’90s and 2000s, and although they’re still around today, they aren’t quite as popular.
I suspect the drop in popularity may also have something to do with the company manufacturing a lot of commercial boilers nowadays, although Sime combi boilers were generally very reliable and reasonably priced.
Fault 1: Printed circuit board fault
There was a major faults with Sime boilers back in August 2013, which affected the Sime 80C, 100C and 110C and caused a number of effected boilers to overheat and become potentially dangerous.
A necessary modification was required for these boilers, and a report issued from the HSE and Gas Safe detailing that any affected boiler must be taken out of operation until it was updated and fitted with a safety thermostat.
However, some of the boilers affected may not have been registered or serviced, and the original home owners may have moved on, so it’s definitely contacting Sime to check if your boiler is affected.
The Fix: If it’s suspected that your Sime boiler is experiencing this fault, my advice is to turn it off and isolate the appliance from the gas, as it could be a serious fire hazard. Please follow the advice given on the HSE website.
Fault 2: Diverter valve failure
If you’re only getting hot water when your heating is on, or your hot water tap is only running lukewarm, it could be a problem with a faulty diverter valve. We’ve actually written an entire blog post on how to diagnose this specific problem.
The Fix: Your chosen gas engineer can either replace the diverter valve, or dismantle the valve to replace the diaphragm washer and spindles inside.
TIP: A common problem was getting water on the electrics whilst removing pumps or diverter valves due to the position of the electrical box on Sime boilers, which is why I always place a plastic sheet and towel over the electrics before working on them.
Fault 3: Boiler pressure too high and climbing higher
This was a common problem I often came across on the Friendly and Super 90 models. I can’t be sure if it was a manufacturing issue or a corrosion issue, but the plate heat exchanger was splitting, causing the cold water to cross over and fill the heating circuit. The tell tale sign being that the pressure gauge would get higher even if the pressure was released and the filling loop disconnected. It’s like the pressure is getting higher by itself.
The Fix: The only solution I know of is to replace the plate heat exchanger, which can easily be done by your chosen heating engineer.
Fault 4: Boiler is losing pressure
If your boiler is losing pressure, and you’ve checked the radiators, pipework and safety valve to find no leaks, the most common fault is a faulty auto air vent which is leaking.
The Fix: The auto air vent can be removed and replaced by an engineer, before refilling and repressurising the system (which is as simple as turning the filling loop until the boiler reaches 1.5 bar).
Fault 5: Boiler failing to ignite
If the pilot is igniting, yet the main burner is not firing up, it could be a problem with the electrics. I find this is a common issue after electrical work has been carried out by kitchen fitters or homeowners adding plug sockets. Usually down to negative polarity, which happens when live and neutral wires are crossed.
The Fix: Test the boiler on a multi-meter to see if the neutral wire at the boiler is live. Get a qualified electrician to thoroughly check and fix the electrics.
Consider a replacement
If you own a Sime Friendly, 90, 90 or 102, these boilers are now between 15 and 20 years old. It may not be cost-effective to repair them, and they also aren’t high efficiency condensing models, so could be costing you more in energy than you necessarily need to pay.
It may be worth looking into seeking a replacement, especially if you’re consistently experiencing faults and problems with your old Sime boiler.
Conclusion
I hope this blog has helped you to diagnose and troubleshoot your faulty Sime boiler – just remember to call an experienced gas engineer unless it’s simply a matter of repressurising your boiler or defrosting a condensate pipe.
Are you experiencing a problem with your Sime boiler that I haven’t mentioned on this list? Either leave a comment below or get in touch with me directly – I’ll be happy to help!
my sime combi .the flame is pulsing when I call for heat and a little worse if I call for hot water
i have a format 80 c lpg in my caravan the dhw and the ch start up for a short time and then lock out wait 3 mins and start again then does the same any ideas
Hi, we have a Sime Ecomfort plus 25 HE and its been problematic ever since we have had it with the same issue. The hot water runs from the tap/shower then goes cold, then hot, then cold etc etc. The problem doesnt happen all the time. In the warrenty period Sime came out and changed the fan which sorted it for a while, then other engineer have changed temperature switches, now we are struggling to get anyone interested in trying to fault find, all they want to do is fit a new boiler. Was thinking it might be the diverter valve? any pointers appreciated.
I have had the same problem and my boiler was still under warranty. The problem was the diverter and circuit board I think. However sime has the worst customer service you can think of. I called for help and it took more than two months to fix the fault. They will avoid fixing it and they will tell you that you need to do power flushing first for example. They will come in and tell you that parts have been ordered and you will never see them again. You need to be assertive to get their support. It is stressful, depressing, the last experience you will want to have. Their customer service agents are the rudest people you can ever meet. when I stated that I needed my boiler to be fixed and when I asked to priortise the job because of children in the property, the supervisor asked me to go to their offices in north to pick up parts from their warehouse. My advice simply dont buy this boilers , dont waste money getting it fixed, replace it.
Is is suddenly taking a long time for hot water to come through the kitchen tap. Water is hot when it does come through. I can stand for a good couple of minutes each time I turn on the tap. My local gas fitter has looked at the boiler.He said to turn on the tap fast and then slow it down. I am not at all convinced this is right as it doesn’t make any difference. There are not any faults shown on the boilet. It is a sime combi can you help please
Have this boiler. The worst boiler ever. Do not waste money getting it fixed. Replace it
Ray. Sime Friendly Format 80E flame cuts out when heating is on need to turn off and turn back on flame doesn’t always come on first time even though the boiler is running now not getting any hot water is it a censor?
My sime boiler was turned on to ch yesterday. After a few hours red light came on and could not get hw . Tried to repressurise it and starts to let water in dial jumps to 2 then it clicks wont let gauge go any further and water is pouring out overflow pipe. Keeps trying to do this itself until I turn off water pressure.
I have a sime ev he ecocomfort but when i set the timer buttons to come on at certain times the clock goes around to the time set but doesn’t click into action to actually turn heating on (as if the clock cant push the clock around when the buttons/tabs are pushed out). Would it be the clock or a circuit board change. much obliged for your time. Simeon.
I have 2012 sime 30/ 50 combi boiler when the unit is called for heat (cast rads) unit fluctuates between high burn and low will level out after 15 mins
Boiler getting a signal to light but not igniting almost as though pub board problem also stops and start about every 2 mins
Can you recommend a 7 day timer that can control a SIME 90?
hi have a sime in my caravan turning tap on then when i come turn off it carries on burning up have to turn off run the tap water red hot .when put heating on it will not always keep coming back on to heat rads had plumer to it thy have put new circuitboard in but still doing the same thank u pleasehelp
Re. Boiler pressure rising to high because of a split heat exchanger . Do you mean the dhw exchanger
Hi,
We have a Sime friendly which is old I know but works fine the only think is it has started to make a loud noise coming from a little black plastic box underneath the ingnighter which only happens when the pump stops, you can feel the vibration by touching the black box,
Any information would be grately appreciated. Regards Terry.
Phone. 07767375294.
Hi I have a prob my gas engineer is struggling with, the boiler shuts off when I need hot water,he says it’s fuming but can’t understand why,have you any suggestions