Compressor not cutting out

[opps]

Hi all

My (15 yr old) Nardi compressor starts up OK, reaches 7 BAR and stays there with the motor running constantly.





From what I have read, it sounds like the pressure switch may be faulty.

A new generic one seems to be about a tenner.

https://www.amazon.co.uk/214124-Com...2&sprefix=Compressor+presure+,aps,160&sr=8-10



The one above looks very similar but it lacks the female nut where it meets the male part on the tank.

Mine looks like this



The other thing I can't work out is how to remove the blue pipe. The amazon replacement seems to have a nut where the blue pipe goes.

 

[HERTS P&D]

Try pushing the metal shroud around the pipe, while pushed up pull out the blue pipe.

Andy

 

[opps]

Try pushing the metal shroud around the pipe, while pushed up pull out the blue pipe.

Andy

Will do, thanks.

So will the new pressure switch use a nut and olive to connect the blue pipe?

And any ideas about the tank nut?

 

[HERTS P&D]

The best person to help you is John Burnerman.

Hopefully he will be along soon.

Andy

 

[Burnerman]

I don't know if you've bought the new switch yet, but have you thought about dismantling the original one? The chances are it'll be bunged up with rust which has occurred over the years. Nothing to really break inside so you have little to lose!
John

 

[opps]

I don't know if you've bought the new switch yet, but have you thought about dismantling the original one? The chances are it'll be bunged up with rust which has occurred over the years. Nothing to really break inside so you have little to lose!
John

I think you might be correct about the rust. When I put my finger in the end of the tank nut it was black. Will try to take it apart if I get the time on Sunday.

Cheers

 

[opps]

Update

I did clean out the old switch but it made no difference.

I worked out how to remove the blue pipe- once you remove the back of the switch there is what looks like a toy black spanner (see middle of photo)



The problem I now have is the nut (connected to the old switch) that runs from the switch unit to the reservoir. I have no idea how to remove it and fit it to the new switch. Initially, I assumed that I just needed to put an Allen key in it and unscrew it, but none of my metric or imperial Allen keys seem to grip anything. The hole inside looks round. The nut can be seen in image 2 and 4.

I guess I will need to order a male to female connector. Does anyone know what size they are?

 

[Harry Bloomfield]

Update

I did clean out the old switch but it made no difference.

Pressure switches are usually adjustable - have you tried adjusting it to a lower setting?

 

[opps]

I have used the red twisty knob thing to reduce the required pressure. It reaches the lower level and still keeps on running.

I was under the impression that the adjustment on the switch was related to the pressure at which the compressor kicks back in. Are you saying that the lower level might have become higher than the setting defined by the regulator dial?

 

[Harry Bloomfield]

I was under the impression that the adjustment on the switch was related to the pressure at which the compressor kicks back in. Are you saying that the lower level might have become higher than the setting defined by the regulator dial?

That was my thoughts, that the switch had maybe drifted in calibration. It switches on when the pressure falls, off when it rises to the setting - with a bit of hysteresis in between. I seem to remember mine doing the same and found there was a microswitch which had failed.

 

[opps]

Next problem....

The new pressure switch has a 1/4 inch female port. The reservoir has a larger male port.

The old pressure switch had an male to female adaptor. I had hoped that it was fitted to the pressure switch by using an allen key. There is no hex inside the fitting, meaning that I cannot remove it and connect it to the port on the new switch. See image



I did measure the male fitting on the reservoir, according to my callipers it is 0.66 inches. The 1/4 inch blanking plugs supplied with the new switch measure 0.4"? I have no idea how you measure BSP fittings but given that the male is approximately 50% bigger than the male blanking plug I guess it means that I am not looking at a 1/2" to 1/4"? So do I need a 3/8 to 1/4?