Ted, your post is confusing and contradictory to the TM's. Your post is telling him to test the glow plugs by suppling them with battery power(unspecified 12 or 24 volts) with a test light(and the comment about a 24 volt test light is irrelevant to the test). While actually powering them with a test light is a reasonable indication of a good or bad glow plug, using an ohm meter as called out in the TM is more definitive(very small range of readings is acceptable, with very little variation).
A simple test with an ohm meter is what the TM calls for. They need to measure 0-3 ohms.
In about 95% of all GP problems, I think about 95% of the time, the problems could be diagnosed and repaired by the OP, simply by reading and following the TM diagnostics, step by step. (rather than reading random responses from posters that want to help but are usually less than 100% sure of all the facts and rarely explain how to test the whole system.
Heres a good read on testing them.
http://www.steelsoldiers.com/500489-post3.html
And yeah, you wussies/nubies that get hurt feeling when we say"do a search", this is exactly why we get tired of re-explaining and linking to old posts that TOTALLY covered a subject, over and over. No wonder the search function results are challenging to read through. (this comment was NOT directed to the OP or any one individual in particular) In the last thread that discussed how we could just ignore it and pass on, well If we do, the forums will be full of incorrect and useless crap! So ignoring it is NOT the best answer!
I think in this threads case, a simple link to a relevant thread would have sufficed, better than a confusing and incomplete answer.
btw, If you think I'm a jerk for saying all this in this thread, don't, I do it because I care about the site and it IS my job as a moderator to try to manage the site.