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Discussion Starter · #1 ·
1998 New Beetle with 87k miles, about 1000 miles after I bought it, CEL comes on about 30 seconds after starting. I borrowed an Autozone scanner which returns codes P3080 and P1156. I can find little info about 1156 but obviously tons about 3080.

I followed the glow plugs 101 troubleshooting here, thanks to Wingnut at TDIClub.com for that.

The issue appears to be zero voltage at the harness - when I turn the ignition on, all plugs on the harness show only the residual voltage (.11 volts), none of them ever show 12V. I checked the glow plug relay, contacts look fine and I can feel it clicking on/off when I cycle the ignition. I've found tons of info on troubleshooting the glow plugs but not much on the relay itself, I've ready it doesn't often go bad.

Is it possible the relay is bad even though it feels like it's turning on and off? Is there a way to actually test the relay or should I just replace it? Anything else that could cause me to have no voltage at the harness?

Thanks.
 

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Discussion Starter · #3 ·
Update - I tested again by pulling the plug from the coolant temperature sensor and then checking the voltage at the glow plug harness. Bingo! With the coolant temperature sensor disconnected I show 12v on the glow plug harness. So off to the auto parts store, new coolant temperature sensor, installed the new sensor and put it all back together and.....no go. With the new sensor installed I'm still getting 0 volts at the glow plug harness.

So does that mean I have a wiring issue somewhere? Or is the relay still potentially the culprit?

Interesting note, when I had the original temp sensor installed, I was getting some residual voltage (0.1v) at the glow plug harness. With the new temp sensor installed I see a solid 0v at the glow plug harness.

Do I need to get the code scanner from Autozone and clear the codes now that I have the new sensor installed? I read that the CEL is supposed to clear itself after 3 starts where the fault is not present. Any help greatly appreciated.
 

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Don't know where you live and what the weather is like, but be aware that the gp's won't come on above 40degF.
 

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Discussion Starter · #5 ·
Don't know where you live and what the weather is like, but be aware that the gp's won't come on above 40degF.
Thanks for the reply but I'd respectfully suggest that is not accurate. A ton of reading on the subject, one good post here: TDIClub Forums - View Single Post - Glow Plugs - What temp do they turn on?

Regardless of when the plugs 'should' be turning off, the consensus is that every time you turn the key, if the glow plug system is functional I should see 12V at the plugs - I'm seeing 0V at the plugs. The actual symptoms here are:

1. The fault code and persistent check engine light
2. Car cranks for at least 3 - 6 seconds before firing.

On the second point, when doing the 'disconnect coolant temp sensor' test, I get 12V at the plugs, the glow plug light illuminates for around 10 seconds and most telling, the car fires instantly.

As I'm already in it I went ahead and ordered a new glow plug relay from ID Parts, will see what that does and report back.

Thanks,
Ben
 
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