Nate, did you ever discover the cause of the horn/beeping? I may have missed the answer, if so please point to message or repost.
you posted: "so now we know that massive glow plug failure causes the indicator lamp to flash and maybe also the horn to toot (I dunno about this part , stay tuned) ."
Any update on the answer?
Thanks,
Chuck
84 300sd
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--- In diesel_mercedes@yahoogroups.com, "Nate" <vwnate1@...> wrote:
>
>
> O.K. Guys & Gals ;
>
> Here's one for the books :
>
> My 1985 (build date Oct. '84) 300TD has had this weird horn beeping & glow plug lamp flashing at initial cold startup , to-day I decided to quick check it thusly :
>
> Test light tip grounded in the throttle linkage on the rockerbox , I attached the alligator clip to the easiest to reach glow plug , turned
> on the key and the lamp lit even though the horn beeped and the dash indicator lamp flashed in time with the horn beeping....
>
> So I removed the GP Relay's black plastic cover and inspected the fuseable link , it passed the lamp test on both ends , screws were tight so I unplugged the lower MPC ,this contains the 5 glow plug wires , then I connected the alligator clip to a known good ground and turned on the ignition key ~ all five relay output pins had current , this showed the relay was O.K.so I then connected the alligator clip of the test light to the known hot wire inside the open relay then I probed each female connector inside the MPC and guess what ? only _one_ lit up the test lamp . the rest were open circuit .
>
> Therefore I tested each glow plug by touching the test light's tip to each glow plug nut and only one lit the lamp ~ so now we know that massive glow plug failure causes the indicator lamp to flash and maybe also the horn to toot (I dunno about this part , stay tuned) .
>
> As I suspected the 25 year old glow plugs may have simply died of old age , I'd already purchased a full set of five Monark brand ones and will hopefully install them to-morrow along with a valve adjust .
>
> I tested in this sequence so I'd discover if the harness between the GP Relay and the GP's had any problems , shorts or open circuits .
>
> I hope this helps , the engine was hard to start , it only began to fire when I released the throttle and didn't touch it whilst cranking until the engine began to fire .
>
> -Nate
> (still learning every day)
>
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