A little bit of caution is advised here.
Relay coils come in two flavors, 28VDC and 115VAC (400Hz). I've learned from personal experience.... using the wrong voltage to test one normally provides a "brief" moment of excitement. Sometimes this "excitement" is accompanied by a bright flash and possible smoke. (To be truthful, it was early on in my aircraft maintenance "travels". On a MD-80, I used 115 on a 28 volt relay with jumpers in the E&E compartment. I got that "flash" and luckily, just some popped breakers. I started paying close attention to coil voltages after
that one.)
