I had a chance to get a multimeter, and it looks like there is about a 75 milliAmp draw on the battery. I think that is a little high or right on the borderline of being normal, from what I've read. It was too cold and dark for me to pull fuses to find out which circuit is causing the draw, but I'll try to get at it this weekend. Hopefully, it's one of the inexpensive parts that you mentioned...

Pete

 

I had a little time to work on this and found a couple interesting things. First, it looks like there is minimal to no parasitic draw when the car is off. Also, I am able to recreate the no-start just by driving a few blocks and then shutting down. When I run VAG-COM during the no-start condition, there is at least one fault code - Power Supply Terminal 30: Voltage too Low / P1602 - 35-10 - - - Intermittent. When I check the battery, it's at about 12 volts. When I disconnect the battery, it slowly works its way back up to 12.5 - 12.6. When I re-connect, it drops back down to about 12. So it looks like something is drawing about .5 volts when the no-start happens. I didn't check amperage.

After I jump start it, the battery goes back to normal and the voltage draw disappears too. I'm not sure what's causing the draw, but I'll have a chance to look at this again and try pulling fuses in another few days.

Also, I checked the temperatures sensor readouts again in VAG-COM, and Audiltr may be right because the sensors showed that temp was around -60C to -180C and kept jumping around all over the place. There are 2 temp readings and they were both really low and bouncing around. I'm not certain which is the CTS and which is the MAF, etc., but either way I think the readings are wrong. I'll probably change the CTS since it looks like it's faulty and Audiltr says his symptoms were exactly how I previously described.

I'll update again if and when I get closer to figuring this out...

Pete

 

Interesting - the low voltage at terminal 30 indicates a low voltage at one of the output pins of your ignition switch. It can happen for many reasons. The ignition switches in this generation of Audis are notorious for screwy failures and internal shorting. It might be worthwhile to just replace it. They're $25 from FCP Groton and pretty easy to change out.

 

I'll give it a shot! Thanks!

 

ECS Tuning has an "Genuine" OEM ignition switch for $25 as well
Audi B5 A4 Quattro 1.8T > Interior > Switches > ES#1896875 Ignition Switch - 4B0905849

I'm thinking about getting this, cheap enough that in my mind I think "why not".

 

I received the new CTS today and switched out the old one. Surprisingly, it took less than 5 minutes. The old one looked a little cruddy - I'm attaching a photo. There was also some white gunk floating in the CTS chamber. I cleaned it all out before inserting the new sensor. I'm not sure if either of these had anything to do with the no-start.

I went on a couple of test rides, and things appear fine. The temperatures still look a little screwy though, and it may take a while before the no-start occurs again. I'm still going to change the ignition switch just in case since it's pretty cheap and doesn't look too hard to do. I actually found one on Ebay for about $8 including shipping, so I might as well give it a shot. Either way, I'll post another update once complete.

Thanks again all!

Pete

 

Any body have any ideas what else could cause this problem? I recently replaces my ICM for a cyl 3 mis-fire, the ICM fixed that problem but Now I'm having the same crancking but no start issue. Driving me nuts. I don't see how anybody stands it not to mention, its embarrassing...car cranking for 30 seconds or so. I read down some other post in this forum so I just replaced the coolant sensor and still having the same problem

 

Another update - I changed the ignition switch, and everything is still fine. I'll post if the problem comes back, but I'm hoping that these two fixes did the trick. Also, I made a write-up of the ignition switch replacement because I couldn't find one that matched my vehicle 100%. However, it's over 1Meg with the photos, and I can't post it here. Does anyone have any suggestions?

Thanks again!
Pete

 

The no-start returned. At least we ruled out the CTS and ignition switch. I'll keep working on it. There is something definitely pulling some power out of the battery when the no-start occurs, so I'll continue where I left off and pull fuses/disconnect wires until I find out what is causing the draw.

I'll start a new thread since we know it's not the CTS now...

Thanks again everyone!

Pete

 

I had a chance to pull wires, etc. and it looks like the alternator/voltage regulator could have been the culprit somehow. I removed it, cleaned contacts and the housing itself, re-installed it, and everything is running fine. Even the CTS readings have stabilized. I don't know how or why. But I'm glad I don't have to spend any more time on this, for now...