I have not checked a wiring diagram, but maybe someone knows ...

If the contacts in the ignition switch go bad, would that cause the glow plugs
to not work ?

I have removed and cleaned the contacts before on the 300D ignition switch.
I imagine repeated use would eventually cause failure.

I checked resistance on all 5 glow plugs from the connector at harness.
Number one was bad so I replaced it.

I checked voltage at the relay on both sides of fuse and it is 12 volts.

I next checked the voltage at each of the five posts on the relay
for 12v when key on, this worked until the relay clicked off.

When in the car I get no to very short glow plug light
(cold morning at 30 - 40 degress F).

I noticed that if I wiggle the key around and go from off to on several
times in a row I can get the glow plug light to come on.

It makes me think ignition switch, if so, how common is ignition switch
failure ? Car is the 300SD 1983 with 263,000.

Do most of you take apart and clean contacts, or just replace ?

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
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