My pre-glow system isn't working. '83 300D OM617
This is the first time I have had any issues with the GP's. Functioned perfectly until a couple days ago.
Cold starts are challenging. I fear for the life of my starter and battery.

Dash light does not come on at all.
Bulb is good.
GP relay is getting 12V at main lead.
Relay's 80A fuse is good.
All GP's are getting equal power (10.9V) with key on.
I can hear the GP relay click off after ~30 seconds.
GP resistance thru harness shows four under 1ohm and one at 2.4ohms.

What else should I check?

it sounds like you have one bad GP. also 10.9 is a little low with just the GP's on. I get 11.4 with all 5 of mine on. you may have a weak battery. one GP bad should not affect the light though. is it starting?
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I never have luck checking the GP when they are in the car. I have to pull them out. Did you pull yours out to check or check them in?

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I have not pulled them yet.

I assumed the problem lies somewhere in the control system since they all quit working at the same time.

you keep saying they quit working... from the meter readings you report, only one is not working.
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

They produce no results. They are not heating my air/fuel mixture.
I went from 3-click cold starts to minute-plus cranking.

That 10.9V GP reading was taken just after an attempted cold start. Battery is new and strong (enough).

It starts, with much cranking and no assistance from the plugs. (Starts easily when warm.)

Everything worked perfectly until a couple days ago when the dash light quit coming on. Now the plugs are not working.

Are you sure that all the plugs aren't working. It can take only one bad one to cause starting problems depending on the condition of the engine. Have you checked each GP seperately to ensure each one is getting juice? If yes, then I would venture that you have a bad plug or two. If no, then check that and go from there.

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I replaced the one GP that had higher resistance.
My GP light came back on as it should.
Car starts almost instantly (like it did before).

$10 for Bosch at Autozone, normally stocked item.

I'd like to know what the part number you got from AutoZone. The price I saw for mine was $17.99. I have the pencil type. Are yours different?

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1984 300SD 148K Gold
1979 300SD 142K Cream
2001 Audi TT Roadster 60K
2005 Chevrolet 3500 13K

autozone part # 80006
9.99 bosch pencil type 81 and up 617 motor style glow plugs
bosch # 0 250 201 039
Made in France. not Germany though.
John
get two at a time, and get your autozone card punched or swiped whichever type card you have... 20.00 adds up quick!
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!