On Thursday, September 25, 2014 9:51:14 AM UTC-4, Harrold wrote:
I have 2 bridge rectifiers that have different ohm readings. They are

GBPC3504. Can you explain to me how to test them out of circuit. I'd

appreciate it.

I'll buy you a beer next time I'm in the Ft. Myers area.

I'm not Greg, but...

The device has four terminals, two marked with + and - which are the DC outputs, and two marked with ~ which are the AC inputs. There are four diodes internally. Diodes will pass current in one direction only, so using an ohmmeter if you placed the meter leads across a good diode in one direction it will show a low resistance, flip the leads over and it will read infinity (open circuit). A bad diode can either fail shorted (low resistance in both directions) or open.

Now your device is square with one corner cut off. That's the + lead.
https://www.fairchildsemi.com/package-drawings/GB/GBPC04A.pdf

With the + terminal at the top left, check the top two terminals (+ ~) in both directions, they should read like a good diode. Then moving clockwise to the left two terminals (~ -) and do it again. Then the bottom two (- ~), then the left two (~ +). If it fails across any of the pairs of terminals, it's bad.