An ohmmeter won't always tell the whole story, at least not on my '83.

All of my plugs checked okay w/ the ohmmeter. Fuse(s) fine. Still no glow plug light. Car started fine but ran rough and stumbled if I didn't press the pedal in about halfway while starting. I knew that some of the plugs were working, but I likely had one or more than one that was very weak.

Replaced all five glow plugs. Light now comes on and all I have to do is bump the key over to start and the motor fires right away.

Check the big strip fuse and the relay, but you will likely need to just replace all five and you should be in good shape.