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Discussion Starter #1
2010 TDI 140000km

This is my second winter with the Touareg. Last winter I noticed as the temperature got colder, the engine would crank slower than normal. During the cranking, the backlighting behind the HVAC temperature displays would flash. I installed a brand new battery and the voltmeter shows 14V when running. The new battery made really no difference (except to my wallet).

Over the past summer, the warm weather cranking even seemed to be a bit slow - with the flashing backlighting. Now that it is cold out again, it is cranking even slower than last winter. This morning the ambient temperature was -32°C and it took about 10 seconds of really slow cranking before the engine fired. The 1000W circulating heater was plugged in for about 3 hours before starting. I notice even at -10°C the cranking is slower than at any temperature last winter.

Is this a symptom of my starter going bad? Failing battery to starter cable? The only code on VAGCOM is a NOX sensor. I will hook up my multimeter to determine battery voltage at the various stages of starting. If I turn on the ignition without starting it, the voltmeter seems to read below 12V (because of the glow plugs I believe).

I've started other Touareg TDIs in the cold and they crank full speed and fire right up. Any suggestions of what to look at?

I miss the 24V starter in my old LandCruiser! (12V truck, 24V starter)
 

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You need to check the cranking amperage along with the voltage. Not an easy or cheap test if you don't have the tools. You may have a starter with excessive mechanical resistance but not enough to keep it from popping off at this point.

Sent from my SM-G930T using Tapatalk
 

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Discussion Starter #3
This morning was warmer (-27°C). If I turn the key without pressing the brake, it reads about 9V while the glowplugs are cycling. Once running, it reads 14V. After warming up, if I shut off the engine and turn the key back on, it reads 13V.

So it may be the glowplug circuit that's causing too much voltage drop. Perhaps a loose ground? Where are all the engine related grounds located?
 

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Just tonight I removed the electrical connector to all the glow plugs and was surprised at how dirty they were.
I cleaned them all with parts cleaner and blew out with compressed air until shiny new. Only took 10mins and cost nothing to do.
We have done 150K so similar kms to you.

Cheers
 

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Discussion Starter #5
I'll check them, but the glow plugs seem fine on mine, it's the starter that seems sluggish.

-35°C this morning - I cycled the glow plugs twice and then cranked. Slow starter, but it did start and run fine. It's supposed to warm up this weekend so I'll poke around looking for grounding problems. I'll try a heavy gauge cable from the starter body to the negative jumper post to see if that helps the starter.

Is the starter on the US driver's side?
 

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Discussion Starter #7
Alas, I sold my 2010 back to VW. I installed a coolant heater on it, and that helped with the cold winter starting. But the starter always seemed slower whenever it was cold.
 

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Hmmm... to late for the OP, but if we are 100% sure the battery is good (have it tested to double check) then the most likely things to quickly check is...

1. The point where the factory battery disconnect was installed, which is the negative battery ground to car chassis. The entire amperage of the system will go thru this point and we have had rare reports of corrosion problems here. Spilling a soda down the front of the seat or wet winter snow shoes that could drain salt water over this area would be great ways for the corrosion to happen.

2. The battery cable terminals on the battery itself.

Why did I pick these two? Because it sounds like a extra resistance problem in the circuit. The more amperage you push thru it, the higher the resistance goes, the more pronounced the problem becomes.

If there is a 3 and 4 it would be to check the connections to the back of the starter and then finally to pull the starter and have it checked off of the car.
 
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