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Gaggia Classic - expressing violently!
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Kelvis
Senior Member


Joined: 21 Sep 2013
Posts: 2
Location: Switzerland
Expertise: I love coffee

Posted Mon Sep 23, 2013, 3:44pm
Subject: Gaggia Classic - expressing violently!
 

Hi there, i have a problem with my GC, it hasn't had a real service in a while, but my budget and my location are tempting me to fix this myself!
Firstly, i have had it for years, normally produces great crema, i've also got an isomac grinder, and some barista experience...
It recently began expressing violently, really bubbly, way too fast (even though the grind is ok). I have never opened it up, but i took basic measures:  replaced the group seal, and i replaced the shower screen and screen block, (7 years old). I'm not that mechanically minded, but it doesn't leak, and i've got a feeling it is getting too hot. Frothing is not a problem.
Lately, i can get away with a decent shot if i make it soon after turning it on, or by running it for a bit before loading the handle (to release the pressure) but if it has been on for an hour, it'll blast my kitchen left and right... As mentioned, i am willing to open it up if its an easy fix... appreciate any suggestions. Also, i have never descaled it... i was told by a service tech. that such machines didn't need it, and i've never seen reason to either.

Cheers,
Kelvis
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SJM
Senior Member


Joined: 17 Nov 2004
Posts: 1,718
Location: CA
Expertise: I love coffee

Espresso: SAMA (2), Maximatic, Cremina...
Grinder: K-10PB, Rancilio MD-50
Vac Pot: no like
Drip: no like
Roaster: HotTop   Huky en route
Posted Mon Sep 23, 2013, 3:49pm
Subject: Re: Gaggia Classic - expressing violently!
 

Sounds to me like a tstat gone bad and not controlling the ramp up in temperature.
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SStones
Senior Member
SStones
Joined: 24 Nov 2012
Posts: 477
Location: Canada
Expertise: Professional

Espresso: Giga 5, ECM Giotto, Rocket...
Grinder: Anfim Milano-Best
Vac Pot: No  :(
Drip: Some $30 thing from Walmart
Roaster: I buy pre-roasted.
Posted Mon Sep 23, 2013, 6:32pm
Subject: Re: Gaggia Classic - expressing violently!
 

Check the element for a short to ground.  Heat the machine up to operating temp, unplug it and with your multimeter set to the highest range, check resistance from each element connection to ground. If you have anything other than infinite resistance the element is cracked and shorting to boiler ground. If so you will need to replace the element.
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,007
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Mon Sep 23, 2013, 7:21pm
Subject: Re: Gaggia Classic - expressing violently!
 

Classics should warm to fairly stable in about 15 minutes.  If you open the steam valve at that point and it is not overly hot, you should not get much, if any, steam.  If the water is over boiling temperture and it steams continuously at even low pressure, it is too hot.

An instant digital thermometer could help.  Often for under $10 US.  You can run the water into a Styrofoam cup and test the temperature.  Mid page 2 below.  about 160F - 170F is fairly common.

Click Here (coffeegeek.com)

Some of the digitals will disassemble fairly easily and then the thermistor can be used to check boiler temperature and temperature surf.

Click Here (coffeegeek.com)

If no coffee does steam come out the group and "brew" temperature?

Not to disagree with SStones, but element failure is a Classic with the element built in the boiler wall, not in the water, is uncommon, also, not impossible.

 
D4F also at
http://www.gaggiausersgroup.com/
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