Golf 2.0 FSI engine starting problems

[AdamD]

This morning when I went to start my Golf (2005 2.0 FSI Comfortline auto), I was initially unable to start it. I turned the key to the ACC position, got all the usual dash lights, radio switched on, etc. When I turned the key to the start position, all I got was a single 'click', but nothing more. I switched off the radio (RCD-510) and tried again, and the car started first time, with practically no hesitation, and didn't sound like it was down on voltage (although I don't have a voltmeter to check). The car got a brand-new battery 2 weeks ago (a brand-new Bosch, supplied and installed by Transporter). Ambient this morning was 8 degrees C - so fairly cool.

I was a bit concerned, but I filed it away into the 'things I must get checked soon' list. I drove the car for around 30 minutes, and then left the car parked for about 2 hours. I had switched the radio off before I turned the car off, so it was off when I turned the ignition back on when I got back to the car. I turned the key and got the exact same problem - not once, but perhaps half a dozen times, it refused to turn over at all. After a few attempts I didn't even hear a click anymore. I disabled the interior lights and still no good. Headlights and other ancillaries all worked fine. I thought I was going to have to get the car towed, but tried again 5 minutes later, and it started first time - and as it had in the morning, the starter didn't sound like it was labouring with low voltage, it just started right up with no delay.

I had experienced this type of problem a couple of times a month or two back, but these were both on cold starts after not having driven the car for several days, and I knew the battery was struggling (it was 7 years old and didn't like going a week or so between the car being driven; I had put the issue down to a lack of battery charge and assumed a new battery would fix it). Now that I have a new battery, and given how easily the car does start when it actually does turn over, I'm wondering if I might have a failing starter motor or some other electrical problem.

I scanned the car with VCDS when I got home. The only issues (other than an unrelated NOx sensor code) are these faults in the Central Electrics module, which have been present since I got the car about 9 months ago:

3 Faults Found:

02403 - Terminal 15 for Interior
012 - Electrical Fault in Circuit

00185 - Control Circuit; Relay for Supply Voltage Terminal 15
010 - Open or Short to Plus - Intermittent

02402 - Control Circuit for Terminal 15 for Interior
010 - Open or Short to Plus - Intermittent

Can anyone hazard a guess at what the problem might be? Any idea what "Terminal 15 for Interior" is for, and if the above faults might be related to the starting issue?

Many thanks guys!

(And I've just checked the car now, after it's been sitting for 3 hours in my garage. Car started straight away, three times now, with no issues... Gotta love intermittent faults.)