strange glow plug issue. STUMPED!!

heres the deal, ive been having an issue with my 2000 beetle glow plug circuit (p0380) ever since i bought my car a few months ago. i have read and completely understand the glow plug 101 thread and many others as well. i have just replaced all 4 glow plugs and the coolant temp sensor with genuine VW parts. the fuses and relays check fine as well.

my issue is the glow plug harness does not recieve power when cold unless the temp sensor is unplugged. as soon as i unplug it, everything works fine. i plug it back in, and no power. this is the second sensor ive put in it and both checked out good with an ohm meter before i installed them. any ideas would be very helpful. thanx

Glow plug really doesn't kick in until you get into the 30-40degF range, so unless the ambient temp in Cleveland is in that range, I wouldn't expect them to get any power...except when you disconnect the coolant sensor like you stated above.

Someone stated there was a way to modify the settings through Vag-com to make the GPs come on at higher temps, but I never looked into the details

now thats interesting. i know im comparing apples to oranges but my dodge cummins air heater comes on when the engine is cold regaurdless of ambient air temp. my hard starting may be the cause of the anti shutter valve or something else. its been around 50 here in the mornings and its a ***** to start. thanx for the info. ill look into this further.

Check your injection timing. If it's retarded it will be difficult to start.

xtremetractorteam said:

now thats interesting. i know im comparing apples to oranges but my dodge cummins air heater comes on when the engine is cold regaurdless of ambient air temp. my hard starting may be the cause of the anti shutter valve or something else. its been around 50 here in the mornings and its a ***** to start. thanx for the info. ill look into this further.

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the cummins will always heat up no matter if its 90 or -90
thats just the way it works
it may be because its an airheater and not plugs but i dont know
check timing
check shutter valve if u havent already