# Help! Thermal Fuse keeps blowing



## Ralphus84 (May 9, 2014)

Hi All,

Thanks for taking an interest.

I bought a Gaggia classic off here a numbe rof years ago and not looked back since.

One day while using it in steam mode it made some funny noises and essentially the thermal fuse blew and I replaced and we carried on our way for another year or so.

On Monday the machine wouldn't switch on. I cracked it open once again and checked a few points with the trusty multimeter to find as expecte it was the thermal fuse again. After some soldering it switched on and we enjoyed coffee for the rest of the day (no funny noises).

Tuesday Morning once again it won't switch on. I have yet to open it up and test some points because I am waiting for the spare thermal fuses and suspect there might be something else causing it to blow.

Any pointers or help with triaging what is wrong would be most appreciated.

Thanks

Ralph


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## AndyDClements (Aug 29, 2016)

My suspicion would be failure of one of the temperature sensors that should switch off the heater when it reaches the right temperature. I say one, but it should be fairly easy to tell which if the machine fails when on brew rather than steam setting. I'm no expert but I'm just thinking, thermal fuse should only go if the boiler is over-heating.

Edit: perhaps the thermal fuse can also go if there's too much electrical resistance. Don't know how much goes through it.


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## Norvin (Sep 10, 2014)

Sounds like the steam thermostat (the one on top of the boiler) is failing. Easy and cheap enough to replace. The brew thermostat is wired through the steam one so even if it sticks, the steam thermostat will stop the boiler from overheating.


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## Agentb (Feb 11, 2017)

Ralphus84 said:


> Any pointers or help with triaging what is wrong would be most appreciated.


 Does the light on the steam switch a) come on immediately you flick the steam switch or b) after it gets to temperature or c) never comes on ?

Does the light then go off after a while or just stays on?

After steaming milk do you switch steam off and run some water into the boiler? If you do a lot of steaming the boiler will be low on water, and you don't want to leave it on steam after you finish.

Thermal cut-off is really high 180+C and you would notice that... 👍


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## Ralphus84 (May 9, 2014)

Agentb said:


> Does the light on the steam switch a) come on immediately you flick the steam switch or b) after it gets to temperature or c) never comes on ?
> 
> Does the light then go off after a while or just stays on?
> 
> After steaming milk do you switch steam off and run some water into the boiler? If you do a lot of steaming the boiler will be low on water, and you don't want to leave it on steam after you finish.


 No lights come on at all.

When I fixed it last it worked fine.

I usually pull the shot (or ocasionally multiple shots), empty the basket, wipe the head and switch to steam.

Then once finished steaming I do a quick clear of the wand and switch steam off then power off.

I have done this since I got the machine.

Do you think I need to switch steam off and run some water into the boiler?

Happy to replace the thermal fuse again when they arrive in the post but wanted to at least have an idea of what could be causing the fuse to blow so easily.


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## Agentb (Feb 11, 2017)

Ralphus84 said:


> No lights come on at all.
> 
> When I fixed it last it worked fine.


 When you say worked fine - what was the behaviour of the steam light when working?


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## Ralphus84 (May 9, 2014)

Agentb said:


> When you say worked fine - what was the behaviour of the steam light when working?


 Normal from what I know. It would come on and go off when temperature was hit.



Norvin said:


> Sounds like the steam thermostat (the one on top of the boiler) is failing. Easy and cheap enough to replace. The brew thermostat is wired through the steam one so even if it sticks, the steam thermostat will stop the boiler from overheating.


 I'll order a thermostat too won't hurt. Anything else worth thinking of too? The cost of the part is more than delivery if I but it seperately


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## Agentb (Feb 11, 2017)

Ralphus84 said:


> Normal from what I know. It would come on and go off when temperature was hit.
> 
> I'll order a thermostat too won't hurt. Anything else worth thinking of too? The cost of the part is more than delivery if I but it seperately


 Normal is light comes on when temperature is hit, light off when heating.

There are two different steamstats available from memory - if want a little more power get the higher temp one.

A MrShades PID and two SSPRs is an alternative but thats a bit more

Good luck 👍


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## Norvin (Sep 10, 2014)

Ralphus84 said:


> Normal from what I know. It would come on and go off when temperature was hit.
> 
> I'll order a thermostat too won't hurt. Anything else worth thinking of too? The cost of the part is more than delivery if I but it seperately


 Maybe some thermal conductivity grease. You can get it from eBay, CPU Grease. Probably not essential though.


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## Michael87 (Sep 20, 2019)

Ralphus84 said:


> Then once finished steaming I do a quick clear of the wand and switch steam off then power off.
> 
> I have done this since I got the machine
> 
> Do you think I need to switch steam off and run some water into the boiler?


 I'm general I think you should to avoid heating a boiler that's only half full. I imagine the top part could get quite hot if left to preheat with no water in contact.

I do this always when I finish streaming because I'm using a timer to put the machine on each morning.


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## Ralphus84 (May 9, 2014)

Cheers everyone.

I will go ahead and replace the steam thermostat too and see if that helps caffinate my day.

Will report back on here if I am successfull or not.


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## Ralphus84 (May 9, 2014)

Right I'm back!

Sooooo... after waiting more than what should have been a 48 hour recorded delivery.

The thermal fuses and steam thermostat arrived (The wife immediately offered to look after the kids so I could get a fixing).

I switched out the thermostat and soldered the new thermal fuse in.

Life was restored and the lights came on.

I have it a good old descaling with Puly and a follow up clean of the head and portafilter.

Been approx a week and its handling like a dream.

Sooooooo...in Summary

New thermostat, New Thermal fuse and a good old clean sorted the problem.

thanks everyone for you speedy responsesand help.


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