Testing a Solenoid valve
- Thread starter Mike2007
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B
breezer
if its for a washing m/c you dont. you bin it and get a new one
You can test the resistance of the windings and use your power equations if it is a DC coil (if you know the wattage of the coil - sometimes printed on the side) An AC coil is a little trickier as there is inductance as well as resistance. You can compare these to a known good one if you have one.
Beware of energising AC coils without the armature in situ because they can overheat as there is no iron to promote the magnetic field and thus back EMF so they will draw too much current !
You can also IR test the coil if they have an earth terminal or test to the surrounding metalwork.
The most common faults I find are obvious burn-out or open-circuit coil.
Beware of energising AC coils without the armature in situ because they can overheat as there is no iron to promote the magnetic field and thus back EMF so they will draw too much current !
You can also IR test the coil if they have an earth terminal or test to the surrounding metalwork.
The most common faults I find are obvious burn-out or open-circuit coil.
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You can use one of these to check for a magnetic field - didn't have a solenoid to hand but picks up the transformer in the charger:
Available from here
(All it consists of is a reed switch, resistor, LED and a battery - if you are feeling inventive you can make your own)
(All it consists of is a reed switch, resistor, LED and a battery - if you are feeling inventive you can make your own)
You can use one of these to check for a magnetic field - didn't have a solenoid to hand but picks up the transformer in the charger:
Available from here
(All it consists of is a reed switch, resistor, LED and a battery - if you are feeling inventive you can make your own)
Thats good I have one of those!
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The one I have does NOT detect voltage. It detects magnetism and has Magnet Stick written on the side of it. Please don't mistake it for a non contact voltage pen - these are two completely different detectors.
The one ericmark links to above does both but costs more
The one ericmark links to above does both but costs more
Many solenoid valves are a combination of soleniod operated pilot valve and a diaphram valve controlled by the pilot valve. The solenoid can be working properly and opening the pilot valve but the diaphram valve fails to open when the pilot valve opens.
The pilot valve is a small often pin hole sized valve in the diaphram that the plunger of the solenoid can close or open. It is then water pressure that moves the diaphram to open or close the main valve port.
New valve is the best and most reliable repair.
The pilot valve is a small often pin hole sized valve in the diaphram that the plunger of the solenoid can close or open. It is then water pressure that moves the diaphram to open or close the main valve port.
New valve is the best and most reliable repair.
B
breezer
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There are many types of solenoid including types with two coils of wire. The pull in winding and hold in winding. As a result any of the sticks may give false readings. The cheaper types has a little reed switch in the nose and a small magnet in the back which you can unscrew to test it is working but both types have problems if relied on. Often the reed has to be in right place to work and very easy damaged. Drop of 1 foot can stop them working. One the standard 3 pin connection you can get LED seals to replace the rubber seal which lets to see power is there but not if solenoid is drawing current.
The more expensive type are more sensitive and give polarity which was why I first started to use them as we were working on a fleet of generators and the field winding came as pairs but someone in the stores had unpacked then and mixed them all up and they were not marked.
The problem with them is light fingers at near twice the price of the reed switch type one can't afford for them to be stolen. But if theft is not a problem they last far more than twice as long.
Although pneumatic are often direct acting the hydraulic types often have a relay built in. The larger ones often have repair kits with all the seals required.
One problem is the current draw is reduced when on the valve and also the valve conducts heat away from the solenoid and the fitters would slip the solenoid off the valve to test the valve and in the process burn out the solenoid. Especially if left off for a long time. Also sometime although they seemed to fit the valve in fact they did not and the extra air space again will cause them to burn out.
Also had problems with the paint brush when someone has painted over the exhaust and causes them to work once then fail but by time one has walked over they will work again. Once then as soon as back is turned fail again.
As to idea of just renew with some costing £100's of pounds I think that is a non option in many cases. It is surprising how long the wrong one will work for. I have seen DC and AC versions being swapped in error many times and once wrong one is on one tends to replace with one of same part number so the wrong one can be repeatedly fitted.
DC are weak on AC and AC tend to burn out on DC.
The more expensive type are more sensitive and give polarity which was why I first started to use them as we were working on a fleet of generators and the field winding came as pairs but someone in the stores had unpacked then and mixed them all up and they were not marked.
The problem with them is light fingers at near twice the price of the reed switch type one can't afford for them to be stolen. But if theft is not a problem they last far more than twice as long.
Although pneumatic are often direct acting the hydraulic types often have a relay built in. The larger ones often have repair kits with all the seals required.
One problem is the current draw is reduced when on the valve and also the valve conducts heat away from the solenoid and the fitters would slip the solenoid off the valve to test the valve and in the process burn out the solenoid. Especially if left off for a long time. Also sometime although they seemed to fit the valve in fact they did not and the extra air space again will cause them to burn out.
Also had problems with the paint brush when someone has painted over the exhaust and causes them to work once then fail but by time one has walked over they will work again. Once then as soon as back is turned fail again.
As to idea of just renew with some costing £100's of pounds I think that is a non option in many cases. It is surprising how long the wrong one will work for. I have seen DC and AC versions being swapped in error many times and once wrong one is on one tends to replace with one of same part number so the wrong one can be repeatedly fitted.
DC are weak on AC and AC tend to burn out on DC.
I tend to find the opposite, pneumatic have pilot valves and hydraulic are direct acting.
I can't imagine it going down very well if we replaced a hydraulic valve every time it stuck
Some of them are a bit of a nuisance as some computerised systems only operate the solenoid for a couple secs to move the slider, then the output goes off ggggrrrrrrr.
I can't imagine it going down very well if we replaced a hydraulic valve every time it stuck
Some of them are a bit of a nuisance as some computerised systems only operate the solenoid for a couple secs to move the slider, then the output goes off ggggrrrrrrr.
I was assuming it was a domestic appliance valve and included water valves under hydraulic.
If the solenoids are indeed the Danfoss ones that you show then the coil resistance is normally approx 100ohms. The Satronic ones are about 2.2kOhms. How many wires go to it? Some have 2 coils, a pull-in and a hold-in coil as someone has already said.
If there is a centre opening, as in your photo, when you know which wire is which and what voltage it is, you can apply power and see if the solenoid will hold a screwdriver in its centre as the armature. (Don't point it at anything in case it fires the screwdiver out!) Getting hold of the screw and pulling on it will give you a sense of how powerful the solenoid is.
If there is a centre opening, as in your photo, when you know which wire is which and what voltage it is, you can apply power and see if the solenoid will hold a screwdriver in its centre as the armature. (Don't point it at anything in case it fires the screwdiver out!) Getting hold of the screw and pulling on it will give you a sense of how powerful the solenoid is.
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