Glow plug failure with no warning light and fault code

[Dave17]

I have a 2002 A4 2.5 TDi Quatrro Sport that struggles to start on cold mornings. The local garage checked the diagnostics and there were no fault codes. Is it possible to have failed glow plugs and get no error codes? I checked the voltage at one glow plug connector and it was OK, I also checked the resistance and found it to be >100K ohms. The garage says this is OK. Sounds wrong to me.

[Alan02]

A test with an Ammeter on the current draw would be easier.Either total amps,or wire in the meter in series to each plug.Or if you dont have ammeter,a test lamp in series to each plug may help.

[Turbokiisseli]

New, 100% working glow plugs should have a resistance of about 1Ohm. You measure them with a voltmeter with one prong on the very tip of the glow plug and 1 on the glow plug body.

I had 2 bad plugs in my old TDI without any fault codes.