# Help needed with OPV mod



## knightsfield (Sep 22, 2014)

Hi

I'm trying to do the opv mod using a pressure gauge purchased of eBay. I've put the gauge on my pf and locked in and turned on the brew switch. The needle is vibrating like mad so making it very hard to get an accurate reading.

I've tried filling the gauge with water and opening the stream wand to get air out of the system.

All the videos I've seen show the needle stationary, rather than moving about.

Anyone any ideas what could be causing this?

Thanks


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## El carajillo (Mar 16, 2013)

Empty the P/F then fill it VERY slowly under the tap, rocking it as you do to remove any air from the gauge and tube. When full hold under brew head and switch on quickly locking P/F, allow some water to flow from steam wand. The needle should be reasonably stable, as the pump is vibratory a small amount of vibration may be noticed. Some gauges are oil filled and this has a damping action on the needle.


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## knightsfield (Sep 22, 2014)

Thank you for the response, tried your suggestion and still get the same vibrating needle.

Thought I'd try emptying the gauge and locking in with no water in it. In this case the pressure builds up slowly and the needle moves round with only very minimal vibration.


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## Bigpikle (Oct 14, 2014)

yep -did mine with no water in it and while it wobbled slightly, it was pretty easy to read.


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## Russ (Nov 15, 2011)

If you don't fill the PF with water don't you run the risk of getting a false reading as you can compress air and not water, and all that? Although I guess it won't compress indefinitely so the pressure will stabilise eventually. Something I also noted when buying my pressure gauge to do the mod was that a lot of the gauges were only listed as suitable for air and not water. I asked a supplier and they said i needed a hydraulic gauge ideally and that these are usually the glycerine filled type. That's what I bought and although it was acouple of quid more than some others it seemed to work well. I used this one (20 bar) http://www.ebay.co.uk/itm/131053838800?_trksid=p2059210.m2749.l2649&var=430230575582&ssPageName=STRK%3AMEBIDX%3AIT and this adapter http://www.ebay.co.uk/itm/111209544598?_trksid=p2059210.m2749.l2649&var=410234875831&ssPageName=STRK%3AMEBIDX%3AIT


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## Norvin (Sep 10, 2014)

Are you trying to measure the pressure with the basket in the portafilter?


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## knightsfield (Sep 22, 2014)

No basket had been removed.

I'll try again with filling it with water and see if I can get it to work without the needle vibrating


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