I am planning on a road trip with my Benz tomorrow and I need to figure out why my glowplug light flashes. This has happen 2 other times and again today. When you turn the key the glowplug light comes on as usual. Once the engine is started the light flashes 3 or 4 times. The car starts and runs fine. I have read that a flashing light before the engine is started, indicates a bad glowplug, what about after the engine is running. Is this something I should be concerned about? Thanks

That is the self diagnostics letting you kow that a plug or plugs are bad. Test each plug at the harness to see which one is bad.

I thought the flashing was supposed to happen before the engine is started. I have looked at the harness connector before, when I was just "poking" around. The connector has 7 pins(female) to it 5 for the plugs and 2 go to the block temp sensors. Unfortunately the connector actually has 8 holes and #4 doesn't have anything in it. So, which "pins" go to the glowplugs. The setup on my car is different than my father's W123. On his when you pull off the connector, there are only 5 pins, which makes it easy. Of course this doesn't help me.
Also when I say it flashes 3 times, that was from memory when it last happened. I just ran to the store and the light flashed 8 times. Oddly it didn't flash when I started the car to come back home. I gather this may have to do with the temp. of the engine. This flashing doesn't happen all the time, that's what is so puzzling.

[Edited by rickjordan on 05-26-2001 at 10:16 PM]

self diagnostic
 

Hello, My 300D was blinking like this on a number of
different occasions last year, whille driving the car.
I learned from this forum about the self diagnostic
at work here. Although I tested the plugs with a volt meter, I never replaced them and this problem has not recurred so far.
So, its best to be ready for a pit stop but I wouldn't
stress over it.
Cheers.

Thanks for everyone's replies and tips. I am now in CT, it was a 200 mile drive from NJ. First thing this morning when we headed out, the light flashed. The car started as usuall. On our way up we stopped once and when I went to start the engine, the light did not flash. Again I am assuming this is because the engine is all warmed up. I will probably just replace all 5 glowplugs for good measure.

Hi Rick, In your diesel engine manual job no.15-710 for W116 300SD up to 1980. It tells you exactly what each flashing light scenario means.

As the previous posters stated you have a bad glow plug, or wire interruption, or incorrect input.

You'll find the whole test procedure in the 617.95 turbo diesel manual under number 15.8-710/5

I hope your trip was great, take care, Patsy.

Well I am back now. The culprit to my flashing light was a loose glowplug wire. I started poking around with the glowplugs wires and found #1 to be loose. I tightened it down and the problem went away. As a side note, with the car loaded down with luggage for 4 (wife, myself, 2 kids), averaging 70 mph., I averaged 29 mpg. Up in MA, diesel was costing about $1.62, whereas super unleaded was costing $1.92.

I thought I would add my odd experience I had today on my 82 300D turbo, so others may stumble on it if they need it. I was driving, engine warm and the glow plug light came on and stayed on. While driving it came on and then went off after a long time a few times with no apparent reason. I arrived home while the light was still on and started with my volt meter testing. I found nothing odd electrically. Note this has not happened before. I took the cover off the glow plug relay box and found the fuse bar hotter than a pistol. I turned the car off and disconnected the the relay box and removed it. When I opened the box, pulled the 4 top screws and pulled the top off, I found the box half full of water and the circuit board soaked. Closer inspection showed two breaks in the o-ring seal under the top. I have been cleaning the engine compartment for a week getting the car ready for a show and must have gotted the water in then. I dried everything off and baked the board in the oven at 250 degrees f. for an hour and put it all back together. All works fine now. This is I guess for those that have a 123 cars and did not know about the o-ring. I hope this helps.
Rick