air pressur switch testing

[B.O.B DOLE]

What is the best way to test one of these with a multimeter
if i placed the red probe on (c) and black probe on (nc) with boiler isolated what reading should i get.and what scale should the v meter be set at.
and with the boiler running how do i test it.

 

[corgigazza]

best way to test is with boiler isolated

With the meter set to ohms either remove connectors from aps and test or remove connector from pcb then test at plug connector, use a piece of manometer hose to gently make and break contacts,
n/c= normally closed, when at rest, should be low resistance 1-10 ohms ie no fan running(n/o will be open circuit)

n/o= normally open is when a reading low resistance 1-10 ohms will be obtained when pressure rises ie fan running and n/c goes open circuit.

 

[B.O.B DOLE]

best way to test is with boiler isolated

With the meter set to ohms either remove connectors from aps and test or remove connector from pcb then test at plug connector, use a piece of manometer hose to gently make and break contacts,
n/c= normally closed, when at rest, should be low resistance 1-10 ohms ie no fan running(n/o will be open circuit)

n/o= normally open is when a reading low resistance 1-10 ohms will be obtained when pressure rises ie fan running and n/c goes open circuit.

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thanks corgigazza
i will try this what i tried was this i isolated boiler tested c+nc which gave me a reading then i fired boiler up and tested c+no and got a reading
but out of cureosity i trid c+nc and this gave a reading but it should not have donr thats what is doing my head in.
can you comfirm that this is wrong thanks......

 

[corgigazza]

You are getting confused with voltage and oms, voltage measures the difference across two points
So c-no with the boiler running should give 0v because the switch is closed(230 volts at c 230 volts at no = 0v)
c-nc will give 230 volts because the switch is open 230v at c 0v at nc).
Try measuring earth to n/o with the fan running 230v (230v at c 230v at nc 0 volts at earth) will give 230 v , isnt it,


may also be low voltage, you can also use a glow pen to check for voltages http://cgi.ebay.co.uk/JMW-GREENLEE-...557095848QQcategoryZ50964QQrdZ1QQcmdZViewItem these are excellent and cheap

 

[B.O.B DOLE]

You are getting confused with voltage and oms, voltage measures the difference across two points
So c-no with the boiler running should give 0v because the switch is closed(230 volts at c 230 volts at no = 0v)
c-nc will give 230 volts because the switch is open 230v at c 0v at nc).
Try measuring earth to n/o with the fan running 230v (230v at c 230v at nc 0 volts at earth) will give 230 v , isnt it,


may also be low voltage, you can also use a glow pen to check for voltages http://cgi.ebay.co.uk/JMW-GREENLEE-...557095848QQcategoryZ50964QQrdZ1QQcmdZViewItem these are excellent and cheap

thanks will try and sus it out thanks

 

[DP]

Can give erroneous readings as some boiler carry out a non operate test. This can give 240 volts on all three terminals when switch operated.