Saab glow plugs look similar to spark plugs. Instead of spark plugs, glow plugs are used to heat and start diesel engines. It takes only two or three seconds for glow plugs, once activated, to generate sufficient heat to warm the engine block so that it's safe to start the vehicle. Saab Glow plugs get it going when the engine is cold or ambient temperatures are low.
More often when a service is carried out your garage will check each Saab glow plug, just like they do with spark plugs and they will let you know how many need replacing.To see what