Jun air 6-25 losing pressure

by Sam
(Tamworth )


I am currently using a 6-25 jun air in a dental surgery.

I am finding that during longer treatment procedures the pressure seems to drop.

It normally works at 6 bar? When the pressure drops it drops to 2 bar but it's not enough pressure to drive the hand pieces and water does not come through either.

It is at least 10 yrs old.

Had the engineers out and he reckons it's the dental chair - air leaking from the water bottle (admittedly the seal has gone ) but this has been a problem before!

Hope you can help

Comments for Jun air 6-25 losing pressure

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Aug 22, 2016
Jun Air compressor problem
by: Bill

I didn't get a sense from your answer if this was a new problem or not, Sam.

If it is ongoing, and is related to longer term use of air as you suggest, my thoughts are the Jun Air is overheating, the motor cuts out on thermal, and when the motor cools, the compressor can start again.

You need to know the air flow requirements of your dental tools and whether the 6-25 has enough capacity for those tools. That MAY be the problem.

Your technician said the compressor was fine. From what you have written I would agree with that, but diagnostics would not have uncovered and thermal cut out of the motor.

The other thing that comes to mind is, how is the power supply? Are many power-using devices (any new for example) on the same power circuit? If you cannot provide the power that the motor requires, that, too, would cause it to overheat and for it to cut out on thermal.

Aug 21, 2016
Response to Jun Air compressor problem
by: Sam

Hi Bill,

Thanks for your response.

Generally it works OK. I'll give you more details.

Every night we switch the compressors off and the oil is drained once weekly.

In the morning they are both switched on.

My compressor works OK through the morning for short procedures but then as soon as I start using it for a long procedure - like 15-20 mins or continuous use , I'll note suddenly the air pressure has dropped.

There is the no water coming through any of the hand pieces either.

On checking the water bottle linked to the chair , there is plenty of water. When I check the compressor , the pressure is at 2 bar. (it has fallen from 6 bar)

I find that when I leave it for 30 mins or so the pressure picks up again , back to 6 bar.
As far as I know the compressor isn't losing pressure when NOT in use.

The bizarre thing is, I had the engineer out last Friday to check mine ( who said the compressor was fine) and now the other compressor (6-25) has also dropped pressure the other day!

Hope this helps!

Aug 20, 2016
Not enough air from Jun-Air
by: Bill

Sam, I can't be sure from your post, but I believe that this is a new Jun-Air problem, yes? In other words, the compressor can deliver enough air for your dental appliances when all is working properly?

That being the case, one thing you said concerns me about this compressor operation. You say the pressure drops to 2 bar. Does this mean that the compressor will not cut in until the pressure reaches that level, or your air use keeps dropping the supply pressure as low as 2 bar?

If the former, I would be checking the pressure switch, as I believe the cut out for the 6-25 is 8 bar, and the cut in will be closer to 5 or 6 bar I would think.

When the compressor reaches cut out and stops, and you are not using air, does the tank pressure drop?

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