So you are telling me the light sometimes won't function if the plugs are bad? I usually pull glowplugs and bench test them as I have seen them ohm out okay and then not work..... But I will start with the ohmmeter 'cause its so easy!! Thanks for the tip! They glow really red when good so it is very obvious. Also, the plugs continue to glow even after the dash light has gone out? Weird, but definitely cool. Thanks all, RT