Gaggia Classic - Flow stopping after heating up

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

Hi everyone,

Another newbie on the forums posting about Gaggia Classic flow issues. I've read all the other posts I can find about this issue and my scenario is slightly different.

I turn my machine on and can quickly smash out 2 coffees once the brew light is on before it seizes up and I get no flow. At this time I can still get steam and water through the steam wand.

Here's a video of the sound it makes once the problem has started. https://www.youtube.com/watch?v=KsTs4eeGX2U You can actually hear it almost work at the 23 second mark and then at 26 seconds it makes the sound where it seizes and I get no flow.

I've opened the machine right up, pulled it all apart, cleaned everything (boiler, opv, solenoid, group head, etc) thoroughly and noticed no blockages or even really any build up of scale. It was pretty oily but that cleaned up nicely. After putting it back together I have exactly the same problem.

I'm wondering if it's the solenoid but is this possible given that it works for a little while? (at least until it really heats up)

Thanks for any insights you can offer.

[JojoS Senior Member Find all posts View Profile Close JojoS]

The only insight I have for now is that I have no idea with what you meant when you stated "I turn my machine on and can quickly smash out 2 coffees once the brew light is on". The video you linked however suggests that there maybe either an OPV or a pump issue.

Do a water debit test to rule out pump issue.

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

Sorry. I mean when I'm desperate for caffeine in the morning I can manage to pour 2 shots of coffee before it seizes up and the water stops flowing.

I'll check out the water debit test. Thanks.

[JojoS Senior Member Find all posts View Profile Close JojoS]

The spurts of water and steam from the steam wand only indicates that your boiler heats up properly. Can you make hot water without the pump seizing? How many ml. of hot water before it seizes?

[LeroyC Senior Member Find all posts View Profile Close LeroyC]

Yeah do the water debit test to eliminate the pump first. There's full instructions on CG and GUG if you haven't found them already and it's easy to do.

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

The spurts of water and steam from the steam wand only indicates that your boiler heats up properly. Can you make hot water without the pump seizing? How many ml. of hot water before it seizes?

From the moment the brew light turns on I can run the pump continuously. It never seizes, I just filled 4 cups. Once it's been running for a while though and I turn it off. When I turn it back on it seizes.

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

Yeah do the water debit test to eliminate the pump first. There's full instructions on CG and GUG if you haven't found them already and it's easy to do.

Thanks Leroy, will test out the pump later today.

[LeroyC Senior Member Find all posts View Profile Close LeroyC]

From the moment the brew light turns on I can run the pump continuously. It never seizes, I just filled 4 cups. Once it's been running for a while though and I turn it off. When I turn it back on it seizes.

When you say it 'seizes', do you mean there's no flow or a reduced flow? If it's no flow at all it's probably just an air lock and should be able to be rectified by running water through the steam wand to prime the pump. If it's a low flow problem then I'm not sure. It sounds like you leave the machine on for extended periods of time. This is not good for small machines with aluminium boilers and could be part of the problem.

[JojoS Senior Member Find all posts View Profile Close JojoS]

Please be aware of the recommended duty cycle of the vibe pump at 1 minute on and 1 minute off. Do you backflush? If you can, do you get a good discharge and a pop from the 3 way solenoid? You should pop the top off and do an ocular inspection to check if anything is loose. Unplug the machine before you do.

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

When you say it 'seizes', do you mean there's no flow or a reduced flow? If it's no flow at all it's probably just an air lock and should be able to be rectified by running water through the steam wand to prime the pump. If it's a low flow problem then I'm not sure. It sounds like you leave the machine on for extended periods of time. This is not good for small machines with aluminium boilers and could be part of the problem.

When it seizes (that may not be the best term for it) there is no flow. The sound changes and no water flows at all. I can get water and steam and through the wand no problems. I can recreate this problem every time I turn the machine on.

We we don't generally leave the machine on for long periods of time. Just turn it on to make a few coffees and then off again. It's been a champ of a unit, 13 years old now. just gotta fix this strange issue and my romance with it can continue.

[timjeffries Junior Member Find all posts View Profile Close timjeffries]

Please be aware of the recommended duty cycle of the vibe pump at 1 minute on and 1 minute off. Do you backflush? If you can, do you get a good discharge and a pop from the 3 way solenoid? You should pop the top off and do an ocular inspection to check if anything is loose. Unplug the machine before you do.

thanks JojoS. I'm not sure what you mean by duty cycle? I recently bought a blind filter to try back flushing so will start that regularly when this flow issue is fixed. I have just had the top open, I stripped it right back and rebuilt it. Sadly the problem was still there after the rebuild.

[Xanthine Senior Member Find all posts View Profile Close Xanthine]

Hi Tim
It could be that your solenoid coil has a heat sensitive fault.
If you have a multi-meter you could try measuring it's resistance when cold and again when it is hot and the fault is occurring.
You would only need to pull one lead from the coil to make the measurement across its terminals.
I'm not sure what the reading would be when cold - probably 100-200 ohms but it should not be much more when hot.
If it is very high - several thousand ohms or more it would indicate that the coil is going open circuit when hot and would need replacing.

Just make sure you have the power off and the machine unplugged before you touch anything inside. If you are not confident working around mains voltages please do not attempt it.
Also watch out for parts inside which could be quite hot.

[LeroyC Senior Member Find all posts View Profile Close LeroyC]

Yeah generally if you've got a good flow of hot through the steam wand but nothing through the group head it's not the pump. It can be the OPV or 3-way, but in this case as it seems to only be happening when hot a faulty 3-way coil is a definite possibility. You can buy the coil on its own as a spare part so definitely worth checking as described by Xanthine above. Good luck.

[JojoS Senior Member Find all posts View Profile Close JojoS]

Duty cycle = the max time the pump is on followed by the rest time before it is turned on again. If I am following this thread correctly, this Gaggia Classic has not experienced any time of back flushing in the last 13 years. I suppose we should always start a trouble shooting thread with a maintenance history background first before trying a diagnosis. That said, the culprit is likely the 3 way solenoid valve and the passages in the lower part of the boiler. Detergent backflush is the most convenient solution and an important part of preventive maintenance before considering replacement. The pump is not seizing but probably reaches it's pressure setting as per OPV adjustment. If you take out the water reservoir and put two water cups with one filled with water going to the pump and the empty to catch the OPV overflow, chances are you will see the water flowing into it at the point when you consider the pump to be "seizing".

[Xanthine Senior Member Find all posts View Profile Close Xanthine]

Sorry, I guess I wasn't specific enough, but the solenoid I was referring to was on the 3-way and not the pump which appears to be working OK.
Trev