On Mon, 15 Apr 2013 11:12:51 -0400, Tom Gardner Mars@Tacks wrote:

On 4/15/2013 3:43 AM, Steve W. wrote:
Tom Gardner wrote:
I'm out of my element trying to test AC valve coils. Usually, If they
fail on me they smoke and crack and smell VERY bad...or, they have no
continuity. But, I've had some go bad with none of those obvious
symptoms. I Googled and for some of the testing methods you need a
magnetomatrix oscifier and capatrometer. There should be an easier way!


inductive ammeter - with AC applied if the coil is conducting at all you
should pick up the amp draw.

Compass and switched DC source. Switch so you can cycle the power to the
coil. Compass to tell if the coil is generating a magnetic field. (Use a
pulsed DC source with a low cycle time for best results)

VOM, non-contact thermometer and the data sheet for the valve.
VOM to measure the resistance of the coil.
NC Therm. to measure the temperature of the coil.
Data sheet to tell you what the correct number should be for a given
temperature.


Does it make a difference if the coil is " satisfied" with a core?

For testing with a meter, no. But if the coil has an intermittent
open, or a thermal open (it quits when it warms up) you almost have to
test it in a live circuit.

For testing with live power, if you don't have a valve body and core
in the hole the coil will be bad in about three... Two... And there's
the smoke - /now/ it's bad.

Don't ask me how I know this.

If you want to disable the valve, you have to pull the wires. Pulling
the coil off the valve head is not a good idea.

-- Bruce --