W210 Glow Plug Testing
 

Last summer, check engine light came on due to glow plug fault. I tested glow plugs with multimeter and found one bad. Car started fine with mild rough idle all throughout the winter. This morning I tested the plugs again and it looks like five out of the six are bad. Which is fine...they're all original. What I'm trying to figure out is how the car made it through winter with, likely, so many plugs out.

This will give me a good excuse to use the HHT emulator on Xentry to see if I can figure out exactly what's going on.

There's no need for a scan tool. It's simply going to say "Glow plug circuit voltage low/0 volts/open" or something like that.

The glow plug is open, simple as that. Just like a burnt out light bulb. Change plug, problem gone.

The glow plug can no longer provide continuity. Luckily your glow plug circuit isn't shorted, otherwise stuff starts smoking

That cars must be insanely hard to start with just ONE glow plug!

My mistake....was having continuity issues with the multimeter....just one plug out, #5.

I had a similar run in as well, I like test lights much better because it's easier to get a positive response.