ohms

[Billy]

just getting started in hvac and wondering if anyone can help me understand how to ohm a contactor coil or gas valve etc.
thanks

[ProTemp]

First off u need a multimeter that supports ohms. Take your leads and measure the resistance across the coil. Your reading depends on what kind of valve you have. Either a 24v wich is more common or a 115v gas valve wich is mainly comercial. Try and compare your reading with a new valve or contactor of the same type or model. If there is a difference between the 2 more than likely your coil is bad.  Also take your leads and see if your coil is grounded to the chasis by switching your meter to the audible ohms setting. If there is a beep your fubar...lol. This test is pretty much standard for coils.

[TECH X]

Here's some gas valve readings that will give you and idea of what to check.  A standing pilot valve will have a magnet coil and a operator coil.  Both will have different resistances.