Ric,
The glow plug indicator in the dash is in series with the glow plugs in the circuit. All the current going to the glow plugs must pass through the little coil and the resistance load causes it to glow. Mine used to glow fairly bright in the dark and after 45 sec to one minute it would be bright orange. I would suggest testing each of your glow plugs individually. If you have one that is not functioning properly the resistance load on the indicator coil will not be high enough to get it to glow. One bad plug on a three cylinder is a 33% reduction in starting capacity. I've learned from experience that the only sure way to test them is to phisically heat each one individually out of the engine. Hold the threaded portion of a glow plug with a pair of pliers against the negative post of a battery. Use a jumper wire attached to the terminal stud of the glow plug and momentarily energize the glow plug on the positive post. You should observe the tip of the glow plug turn red and the whole probe should glow. I have had glow plugs which show a resistance reading on an ohm meter fail the heating test or some that only heat one little spot near the base. Only heat the glow plug up to the point of turning orange or else it could vaporize like your little indicator coil although it does take several seconds to heat up. Remember it will heat up faster than it does when installed in the circuit since the resistor (indicator) coil is not in the circuit. The resistor also serves as a safety so it is impossible to burn out the glow plugs by energizing them too long. I don't know if you have had any experience with the old GM 5.7/6.2 or Ford 6.9/7.3 automotive diesels but most of them were equipted with 6v glow plugs so the preheat time was only about 8 to 10 seconds. The trouble with this set up was if the timer somehow failed or if someone tried to bypass or jump the circuit, after 15 seconds, POOF! eight burnt out glow plugs. So I always repaired the systems properly to safegard those precious glow plugs.
Stephen
