Coolant Warning light and the A/C...

[DudeDah]

Ok, so got an oil change yesterday at a reliable Indy shop (not saying the issues are related just giving all the background info). Yesterday I noticed that while sitting in the pickup line at school with the car parked and engine running that the A/C stopped blowing cold and was lukewarm. When I started driving again though the A/C cooled back down. Today as I was driving I noticed same issue, A/C would blow cold while moving but get lukewarm when stopped. When I went to pick up my daughter today, the A/C got lukewarm again while I was parked with the engine running but then...the COOLANT LIGHT went off and needle was close to HOT. So, Shut the car off. Drove to a nearby street to pop the hood and the level in the reservoir was near max and I could not detect any noticeable leaks but the coolant light was still on with A/C running lukewarm. I shut the car off for a bit and then restarted, turned A/C OFF...then needle went to halfway and I got the car home fine, no more warning light, no noticeable leaks and reservoir still near max.

Does anyone have ANY idea what might be going on here?

[jstarr427]

sounds like you're radiator fans aren't turning on. start by checking fuses, then maybe try VAGCOM to activate the fans. could be the fan controller went, vs the actual motors themselves.

[SinCityA6]

Ok, so got an oil change yesterday at a reliable Indy shop (not saying the issues are related just giving all the background info). Yesterday I noticed that while sitting in the pickup line at school with the car parked and engine running that the A/C stopped blowing cold and was lukewarm. When I started driving again though the A/C cooled back down. Today as I was driving I noticed same issue, A/C would blow cold while moving but get lukewarm when stopped. When I went to pick up my daughter today, the A/C got lukewarm again while I was parked with the engine running but then...the COOLANT LIGHT went off and needle was close to HOT. So, Shut the car off. Drove to a nearby street to pop the hood and the level in the reservoir was near max and I could not detect any noticeable leaks but the coolant light was still on with A/C running lukewarm. I shut the car off for a bit and then restarted, turned A/C OFF...then needle went to halfway and I got the car home fine, no more warning light, no noticeable leaks and reservoir still near max.

Does anyone have ANY idea what might be going on here?

IIRC the A6 has 2 cooling fans. Both will run continuously when the A/C is running; pulling outside air across the A/C Condensor. When the A/C is not running, they will activate based on coolant temp. I would check to see your fans are running by keeping the car in park with the A/C running. You should be able to pop the hood and see (and hear) them. If the fans are operating the way they should, then I would check the refrigerant levels in the A/C system.

[jstarr427]

this^^ you should be able to see and hear the fans running. I believe they are PWM controlled to vary in speed based on AC load/demand. scan it and post the codes!

[DudeDah]

Gentlemen...THANK YOU. I appreciate the info. I tried doing some research and it seemed the signs were leading towards it being fan related. Possibly a fan control module or something of that nature. I am afraid to drive it to my favorite Indy shop which is probably 20 miles away and have been waiting for a shop that is walking distance (not far enough that the car will even get warm) to scan it and take a look but I think the guy is on vacation because they haven't been open since Friday. I'll try the troubleshooting methods listed above, I did notice when the car was OFF that the passengers side fan was turning on and off, but did not notice what the fans were doing while the car was running and the A/C was on.

On a related note to this issue, I think I am migrating forums...

[jstarr427]

Glad to hear you're headed in the right direction! If you're hearing the fan randomly turn on and off when the car isn't running, that sure sounds like a fan controller going nuts. If you keep the AC off to reduce heat load, and drive the 20 min to the shop, you may be ok as long as you watch the temperature gauge.

[SinCityA6]

Gentlemen...THANK YOU......

On a related note to this issue, I think I am migrating forums...

Sorry if I am being dense, but what does this mean?


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[DudeDah]

Sorry if I am being dense, but what does this mean?


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Oh, I normally use a different forum but it seems as of late it's been tough to get useful information there with issues that are more...nuanced I guess. I posted here and in a matter of MINUTES had information leading me in the right direction. I think I will be coming here first from now on, that's all.

[SinCityA6]

Glad to have you!


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[boywonder]

If it isn't fan related, it could be the thermostat? It's a known issue on the 3.0T.

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[DudeDah]

this^^ you should be able to see and hear the fans running. I believe they are PWM controlled to vary in speed based on AC load/demand. scan it and post the codes!

I went into the garage this morning and started the car and turned on the A/C. I could see both fans turn on simultaneously from time to time for just short bursts. BUT I didn't let the car get up to a temperature that moved the needle. I have an appointment to take it to the shop first thing in the morning. Sound like the thermostat at this point or still potentially fan related...or are these useless questions without providing codes? ;0)

This car really has been much better than my B5 but I am now at the 125,000 mile point and just made my last payment on it last month...

[jstarr427]

I beleive when I first turn the AC on in my 09 the fans come on, ramp up to full speed, and then calm down and stay on at lower speeds consistently. It does this even with the AC on when its relatively cool outside (65-70 Deg) and the Temp is set at 72. If the car was blowing warm air but wasnt overheating I'm still thinking Fan issues.
It's anyone's guess without codes, if the T-stat is the issue, you'll likely get a code for that. However I've never seen one fail in the closed position.

[DudeDah]

I beleive when I first turn the AC on in my 09 the fans come on, ramp up to full speed, and then calm down and stay on at lower speeds consistently. It does this even with the AC on when its relatively cool outside (65-70 Deg) and the Temp is set at 72. If the car was blowing warm air but wasnt overheating I'm still thinking Fan issues.
It's anyone's guess without codes, if the T-stat is the issue, you'll likely get a code for that. However I've never seen one fail in the closed position.

Sweet, I'll ask the mechanic to write down the codes for me and post what he finds. This is my second Audi and you think by now I would have gotten a VAG-COM of my own but...there IS a Mac version now correct?

[DudeDah]

Just came from the mechanic and he said its the fan control module. Apparently the drivers side fan was bad and it "locking up" threw amperage back to the module and fried it. Getting a new module and both fans for just over $1000...

[jstarr427]

Glad the car is on the way to getting fixed. His reasoning sounds plausible- although I think sometimes its more due to excessive current draw from the fan through the controller that fries it.. I think they do make a mac version of Vag-Com now. If you own multiple Audi's/VW's its definitely worth it. I've got one.

[DudeDah]

Glad the car is on the way to getting fixed. His reasoning sounds plausible- although I think sometimes its more due to excessive current draw from the fan through the controller that fries it.. I think they do make a mac version of Vag-Com now. If you own multiple Audi's/VW's its definitely worth it. I've got one.

You seem like a good guy to ask...what is your take on timing belt/chain replacement? I THOUGHT I heard the C6 used a chain which was more durable than a belt and could go longer until it was necessary to change it....or is this just plain WRONG?

[SinCityA6]

You seem like a good guy to ask...what is your take on timing belt/chain replacement? I THOUGHT I heard the C6 used a chain which was more durable than a belt and could go longer until it was necessary to change it....or is this just plain WRONG?

All C6 models use timing chains. They are more durable than a belt and are considered "maintenance free". However, when they start to go, it is a major repair job. The chains are located at the rear of the motor; sandwiched between the engine and transmission. Based on that, replacement is something that should be done when signs of wear are becoming apparent. These signs are an extended rattle when cold starting. A brief rattle (1-2 seconds) is ok but anything lasting longer is a sign of wear.


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[DudeDah]

All C6 models use timing chains. They are more durable than a belt and are considered "maintenance free". However, when they start to go, it is a major repair job. The chains are located at the rear of the motor; sandwiched between the engine and transmission. Based on that, replacement is something that should be done when signs of wear are becoming apparent. These signs are an extended rattle when cold starting. A brief rattle (1-2 seconds) is ok but anything lasting longer is a sign of wear.


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I remember on my B5 that the water pump, thermostat and tensioners were all "right there" and when you did the timing belt and it was advised to knock out those items while you had the front of the car pulled off. Is it the same case with the C6? Are those items on the back of the engine near the chain? Thanks for all this unrelated info BTW...