# Gaggia Classic pressure gauge build log



## Michael87 (Sep 20, 2019)

Hi all,

I just fitted a pressure gauge to the Gaggia Classic (pre 2015) and took some photos to document it in case anyone else wants to try.

I used a kit from ebay (link) which is the gauge and all necessary connectors.

Step by step:



Disassemble machine: remove boiler/OPV/solenoid and all the cables from the front panel to clear out the space. I left the pump in.


Measure a space for a 40mm hole (my kit was 40mm). Look at my first photo and do not go any lower than this, or the boiler will get in the way.


Make a hole. I drilled a pilot hole and then used a 40mm hole saw (link) plus arbor (link) to cut the hole. That arbor uses a 11mm hex bit which is very large - check it fits into your drill (many are 10mm max). I then filed the hole to widen it a little so the gague would fit properly (it has a plastic groove at the base which seemed to make it a little over 40mm diameter). Someone else recommended using a 40mm metal hole punch (e.g. link) and I would agree this is better. My hole saw produced a load of razor sharp metal shavings that were very awkward to clean up.


Mount the gauge and bend e copper cable so it is not in the way of other things. I had to mount/unmount it a few times to make it fit.


Cut the PVC pipe connecting the pump to the OPV. I cut mine about 2cm from the pump. Mount the T-connector of the pressure gauge to the pipe.


Replace the boiler and all the parts. I had to pop the pressure gauge out to get the boiler in, then it would (just) pop back in.


Test with a blind filter!

It took me about 90 minutes, not counting time to find a drill that can fit a 11m hex arbor.

I can't find a way to link photos (the "Insert other media" didn't work with these links), so here is the imgur album:


http://imgur.com/rrtP1AJ


Here's the finished article.


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## Badgerman (Nov 23, 2017)

Michael87 said:


> Hi all,
> I just fitted a pressure gauge to the Gaggia Classic (pre 2015) and took some photos to document it in case anyone else wants to try.
> I used a kit from ebay (link) which is the gauge and all necessary connectors.
> Step by step:
> ...


Thanks. Great write up and links. Appreciated.

If done the opv is there any need for this?


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## ashcroc (Oct 28, 2016)

Badgerman said:


> Thanks. Great write up and links. Appreciated.
> 
> If done the opv is there any need for this?


It's not really essential unless you're also fitting a dimmer to pressure profile. Nice to have though.


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## MartinB (May 8, 2011)

I have a gauge on my Gaggia (which i'm hoping to drag out of the garage and recommission soon) - the needle on mine isn''t smooth like yours, perhaps i've got an airlock on mine or something, unless yours is a liquid filled gauge and mine isn't?

Great write-up


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## Michael87 (Sep 20, 2019)

Badgerman said:


> Thanks. Great write up and links. Appreciated.
> 
> If done the opv is there any need for this?


 Going in it was just for the OPV and for looks, and because I thought it would be fun to watch (it is!).

Now that it's in, I am noticing the gauge drop during the shot (~11 to ~6bar), presumably as the puck is eroded and puts up less resistance, so I'm wondering if there's any diagnostic value. I'll keep an eye on it.

Also I notice the pressure slowly rising as I turn the steam on, so it might help me steam surf. If I can steam milk without going through a full cycle, it will save me a minute at least prep time. It's probably not as reliable as timing it, but it's easier with no hands free!



MartinB said:


> I have a gauge on my Gaggia (which i'm hoping to drag out of the garage and recommission soon) - the needle on mine isn''t smooth like yours, perhaps i've got an airlock on mine or something, unless yours is a liquid filled gauge and mine isn't?
> 
> Great write-up


 Thanks! This one isn't liquid filled, and it does vibrate but around a very narrow range.

Interesting to speculate why, as I've seen portafilter gauges move much more and heard they need liquid damping. Perhaps it's because this is closer to the pump and the OPV is shielding it from bigger pressure waves in the downstream components (eg air in the boiler or portafilter)?


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## MartinB (May 8, 2011)

Michael87 said:


> Going in it was just for the OPV and for looks, and because I thought it would be fun to watch (it is!).
> 
> Now that it's in, I am noticing the gauge drop during the shot (~11 to ~6bar), presumably as the puck is eroded and puts up less resistance, so I'm wondering if there's any diagnostic value. I'll keep an eye on it.
> 
> ...


 When I get it back up and running i'll experiment with it and probably post a video up!


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