1993 300SD W140 glow plug issue

[mccark]

Hi all,

Been reading the posts on all the glow plug issues but still have questions.

Problem:
Turned the key, waited, no glow plug light, waited some more, started up (it was warm). After 10 seconds of running, glow plug light came back on for several minutes while driving before going out.
That was yesterday.

Today:
Turn key, wait, no glow indicator light. Started, but obviously forced, started very rough. (not going to make a habit of that) Glow plug light came on after startup, then went off. Let it run for 15 minutes until warm, stopped engine, turned on ignition, no plug light....

Question(s):
Is this a sign of a relay not dropping in/out of a circuit?
Are glow plug circuits in series or parallel?

What's first, clean the relay contacts and check the fuse?

Bosch shows 16.83 ea for plugs, seems reasonable, but I am unsure of my options.

Lastly:
Thanks,
kevin