This is all done assuming a cold engine.

After turning my key to pre-glow the glowplugs, I have noticed that my glowplug light SOMETIMES comes on, and sometimes not. No matter the temperature, the glowplug light only stays on for about 3-4 seconds max. And that is only when it comes on.

Sometimes when I turn the key and notice the light has not come on, I turn the key off, then back on until the light comes on just to make sure my glowplugs will heat up. I'm not sure if it actually does anything, but it makes me feel better and it only takes a couple seconds to turn the ignition off then on again.

I understand the light is supposed to stay on about 10 seconds (cold engine obviously), and on my other 300sd, stays on for longer sometimes.

I understand how and what to do to check the resistances in the plugs, the stripfuse, and the relay, but I'm just wondering if the fact that the light stays on for only a few seconds would indicate any single component is faulty before having to check everything (not to mention its completely dark and am alone)?

I know that the light will not come on if one or more of the glowplugs are faulty, but since my light comes on only intermittently, I don't know if any glowplugs are bad.

IF the light's short "on-life" IS NOT normal, then I'm guessing it may be the timer that is to blame. I have a spare parts car as well and all parts work on it, so parts are not a problem.

Its getting colder out everyday and want to make sure the preglow system is in tip top shape this winter in my new baby!

Thanks!

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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

ALSO, I'm guessing the best way to test the actual timer is how I would test the relay, but hold the + wire from my meter in the female pin on the relay until the meter reads 0, indicating that the timer has turned off. This would tell me how long the timer was keeping the relay on, regardless of the light on the dash.

But even knowing that, I'm not sure where the timer is...
is it an integrated part of the relay?

This still doesn't answer my question about the light coming on intermittently, unless the timer is the culprit causing this as well.

Thanks again.

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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

I find it easy to tell when the glow-plugs turn off by watching the dome-light for brightening. In the 60x cars the light turning off indicates you may start the car, but the glow does not go out with the light. Not sure how the earlier system works.

__________________

Gone to the dark side

- Jeff

The amount of time is based in part on the ambient temp. They will also stay lit for something like 30sec after the light goes out. The light should ALWAYS come one. Check out diesel giants howto.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

The light-brightness thing is a neat trick. I usually sit quietly and listen to the relay and wait for it to click off. Both work equally well, but you get to listen to music!

I've checked out the dieselgiant DIY thing. It doesn't have anything pertaining to my question really...It basically lists how to check everything, which I don't have any problems doing.

I think the glowplugs are staying on the correct amount of time, as I can hear the relay "click" off, after checking. BUT I'm just not understanding why the dash light goes off so quickly or why it is intermittent.

Obviously I need to check everything out with my meter, but I posted this thread to find out if anyone has had a similar experience and could possibly direct me to a direct cause of an intermittent function of the glowplug light. Also, I have to wait until tomorrow to check out everything and just wanted to see if I could find out anything about the intermittent light tonight beforehand, that also might save me some time.

Thanks for the recommendations so far!

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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

Check for bad plugs first. This will cause the lamp to extinguish early.

ah! This is what I wanted to know! I was under the impression that if there was a bad plug, the light just wouldn't come on at all.


Thanks for giving me a headstart on where to start!

And also, just for knowledge, I'm still wondering about the glowplug timer. Am I correct about the timer being part of the relay component itself?

__________________
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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

I know mines a different outfit altogether but my 190 D as the same issue. Even when I've got all new glow plugs in and they are all reading appropriately on the meter my glow plug indicator is still erratic. Nonetheless my glow plug relay is like clockworks, pert near 32 seconds to the second. When it's bit chilly out I just let them cycle completely. Often times when it's cold out, ironically my glow plug light stays on longer and more conistently while they cycle the second time after ignition than it does prior to ignition. More curiosity to me than anything else...it always fires easily. Best to ya,

Jim

When one of my GP's failed, I did not get any light at all on the dash. Did the ohm test, found it, replaced all, just for grins, problem solved. I believe the timer is in the relay itself, the "other" plug you see on the relay is the timer.

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83 SD

84 CD

I'm not sure about yours, my experience is limited to the 602 and 603, and the glow plug light does not come on during the start cycle if there are glow-plugs burned out (1 or two of 2-6).

I do have one car doing the same thing yours is, light goes off after a couple of seconds, but the glow cycle is normal. There are two timers, one being the one that is temperature dependant (glow plug light) and the other just a timer (glow plugs), with the light turning off right away you just don't have an indication of when to start. No biggie, I'm going to diagnose it eventually, ... figure either it's the temperature sender or the gp relay module, I have spares of both.

Actually, I'm hoping you figure it out first so I know which one to replace.

__________________

Gone to the dark side

- Jeff

Babymog - are you parting out any parts from your "parts car"?

I need a drivers side "hand hold" handle, which is above the just drivers head.

Thanks, if you can help.

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Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

Probably will be getting rid of parts, after I finish disassembling and choosing parts to keep as spares (such as the powertrain). As far as interior, I should have the (palomino) assist handles but I haven't removed them yet (you know how hobby projects are).

__________________

Gone to the dark side

- Jeff