glow plug indicator isn't working... what do i do?!?

[75mercedes07]

alright, we just got done with the glow plug replacement on saturday, and what a difference it makes... but now the glow plug indicator isnt really lighting up. so i dont know when to pull the pull start or how long to let the thing glow. what should i do?

[pdxwaker]

My glow indicator doesn't light for a good 30 seconds... try an _extended_ glow cycle and see if you get any idication. Also, my '73 indicator is much dimmer than my '69... I may need to replace the '73...

[MB-Owner-in-ind]

When cold my '77 300D takes about 30-45 sec to cycle. If you hear a click then it is done cycling.

[Ken in NC]

If your alternator warning light is working, you can watch it to determine when you have pulled the glow knob out far enough to engage the glow plug circuit....it will dim slightly.

As far as how long to hold it in the glow position, that will depend on your outside temperatures. Just experiment with it

[katja]

you mentioned in your previous thread that when you first installed the new parallel glow plugs, the ground wire was still attached, and that the glow light became super bright, very fast....

I think that light saved your new glow plugs and in turn, probably burned itself out. Glad you removed that ground wire!

The glowing filament in the dash light really acts as a resistor in series with the four glow plugs to control the current (in a strange way, it's like a 5th glow plug...I was so curious about this system I read all the details on the Mercedes service CD). With the parallel plugs wired to ground, the filament in the dash light absorbed the dead short that was created....if it wasn't there, my guess is your new glow plugs would have burned out within a few seconds.

I read your posts with interest because I have a '76 and was considering the new-style glow plug upgrade, but was told that the glow plug light (resistance indicator, as it is referred to in the manual) had to be disconnected as it drops the current too much. I think that light is too cool to get rid of, it draws much more attention than the simple yellow light on the newer cars!

I still have the series system in my 240D, and who knows how old the glow plugs really are. Although it only got down to about 33 F this weekend, my car always starts within one second, but idles a bit rough for a few seconds (my car also has 250K+ miles on it). I have no idea how it will do at say, 5 degrees, it never gets that cold here. I love using the block heater though, my car starts so smoothly it's like summer, and heat comes out of the vents right away.

I think I read somewhere that the pencil style glow plugs heat up in 7 seconds, and on a really cold day, maybe 30 seconds would be the maximum time you'd need to pre-glow. Guess that's a lot better than the whole minute you have to hold that heavy knob out with the old system!

-AC
1976 240D "Katja"

[75mercedes07]

Originally Posted by katja

you mentioned in your previous thread that when you first installed the new parallel glow plugs, the ground wire was still attached, and that the glow light became super bright, very fast....

I think that light saved your new glow plugs and in turn, probably burned itself out. Glad you removed that ground wire!

The glowing filament in the dash light really acts as a resistor in series with the four glow plugs to control the current (in a strange way, it's like a 5th glow plug...I was so curious about this system I read all the details on the Mercedes service CD). With the parallel plugs wired to ground, the filament in the dash light absorbed the dead short that was created....if it wasn't there, my guess is your new glow plugs would have burned out within a few seconds.

I read your posts with interest because I have a '76 and was considering the new-style glow plug upgrade, but was told that the glow plug light (resistance indicator, as it is referred to in the manual) had to be disconnected as it drops the current too much. I think that light is too cool to get rid of, it draws much more attention than the simple yellow light on the newer cars!

I still have the series system in my 240D, and who knows how old the glow plugs really are. Although it only got down to about 33 F this weekend, my car always starts within one second, but idles a bit rough for a few seconds (my car also has 250K+ miles on it). I have no idea how it will do at say, 5 degrees, it never gets that cold here. I love using the block heater though, my car starts so smoothly it's like summer, and heat comes out of the vents right away.

I think I read somewhere that the pencil style glow plugs heat up in 7 seconds, and on a really cold day, maybe 30 seconds would be the maximum time you'd need to pre-glow. Guess that's a lot better than the whole minute you have to hold that heavy knob out with the old system!

-AC
1976 240D "Katja"

if it's true that the glow plug indicator burned itself out, (which makes sense) then would there be anything i could do to replace it, or make it light up like it used to? thanks for all the info and help!!!

ra