wizardofoddd

new here, first post. please be patient with me.

i've got a 2007 s8 with 5.2 v10. it isn't perfect, but it's mine.

it seems like the a/c was cruelly cold last year but seems a bit weak this year. the lowest vent temps match the ambient temps.

codes -
00470 company comfort data bus in single wire
00065 rear left footwell heater - electrical fault
00020 motor for blocking flap defrost and body vents right - mechanical failure intermittent
02596 rear brake pads worn - implausible signal

ambient temp about 60
high pressure 125
low presssure 20

so one of the lines is frosting up (high pressure line??) i can't hear the compressor clicking on and off and the needles on the gauges don't dance around the way i've seen before. i'm assuming it's either a bad clutch on the compressor or relay for compressor.

i dropped the belly pan to look at the compressor, but instead i found where the alternator is located. it's tough to snoop around in there and identify anything without tearing things apart. the fuses labeled for the a/c are in good condition.

if someone could let me know if i'm on the right path, where the a/c relay is, and where the compressor is, i would appreciate it. any other advice on clearing the other codes is a big help too. thanks

wizardofoddd

i've done some work on the car recently, it's possible that i've bumped some connector loose. i'm usually pretty detailed and careful, but it is possible.

it has a new filter for the hvac.

ltooz_a6_a8_q7

If the ambient temp is 60F, your pressures seem to be a little low but compressor works. Evacuation and recharge may fix the problems.

http://www.dognmonkey.com/audi/hot-a...ith-ac-on.html

MP4.2+6.0

Get a/c recharged. Do not use the can type crap or you risk blowing compressor. As you already (didn't) see, if you blow the compressor, besides the high price it is a world of hurt to get it out and in--gear driven on an S8. Refrigerant fill is by weight. It is just over 600grams--less than a pound and a half--so far less than older vehicles were, and also why the can crap is dangerous to use since so easy to go overboard. Any A/C shop can do it with standard recharge gear. There is no "special Audi" magic here.

Audi compressors for last 15 years plus do not use clutches, so you won't be hearing anything there. They use duty cycles--a signal telling compressor what percentage of the time to operate.

None of your codes would get at basic failure to cool sufficiently AFAIK. System losing some of its charge and then not working well is known on D3's. Comes up every year starting about now, at least for our Northern Hemisphere members. BTDT myself, and recharge got it back to strong again like it had been earlier.

wizardofoddd

thanks for the advice.

i'm going to get drained and recharged on weds. i'll let you know how it turns out.

any advice on sorting out the other fault codes??

MP4.2+6.0

In general, clear codes and see what returns.

First isn't known to me but might clear. If that is not VCDS speak though, it may be another code reader garbled code.
Second is a code 95% of all older D3's probably already have. You replace the in line ducting heater under (US) driver's side seat--move driver's seat full forward and you will see it right there in the floor. Comes out with just a screw or two. Problem is part is like $3-400 via discounted dealer. It's only a booster function for regular coolant driven heat. If you live in a cold place and folks in back of car a lot, you may want to restore it.
This needs to be run down. But it might clear. Look at when fault date and number of times detected were. If yesterday and/or lots of instances it coded, it probably is a legit code. If years ago and only one or two incidents, likely clears.
Fourth is likely mis set rear brake pad thickness when they were replaced. Search for procedure on how to set thickness correctly with VCDS. Procedure is pretty unforgiving of even slight variations to the exact steps.

wizardofoddd

thanks for the info. i'll provide a bit more insight....

a/c update-
today was warmer, with a 70 ambient temp, my a/c vents were at 60. so it's weak but working.

i'm getting fault codes from vcds. i wish i could just copy and paste the results. oof
i have cleared many faults as i've been working on the car, but these are the codes that always come back.

fault 00470 company comfort data bus in single wire
from what i understand this is a secondary fault that allows the rest of the hvac system to work even if theres a component failure. so this mightvclear once i get the other two faults remedied?? although i have read something about a power failure on pin 32, but i haven't gotten involved enough to know what that means

fault 00065 rear left footwell heater - electrical fault
understood!! i'll look into it. i know there are quite a few a8 parts cars around. maybe this is a good opportunity for salvage parts??

fault 00020 motor for blocking flap defrost and body vents right - mechanical failure intermittent
this is a new code. it is intermittent. i was hoping that it would have something to do with bringing air thru the a/c. but i haven't found a lot of info on this code...

fault 02596 rear brake pads worn - implausible signal
i have done the procedure a million billion times and it never damn takes. there is also a line of data that says 9.83v. so maybe some corrosion in a connector? or maybe a bad connection to the p brake actuator?? i'm not exactly sure where the voltage is being measured at.

thanks again

MP4.2+6.0

Short version--weak but working on AC really sounds like low refrigerant. Been there, felt that.

On others, yes maybe find the floor heater element via junkyards. Problem is given scans folks post, like 90% + of them seem to be toast already. Both mine died along way too. Thus, be sure you get it from a place with free return if DOA, and you test it right after install. Unlike many parts swap outs, this one is very easy so lost labor for a bad second hand part is low.

Can't answer 00470, but code definitely not connected with the floor heater one lots of folks have had, me included. Maybe a control head I suppose, but even there my rear controls (4 zone) started to get balky and not want to change temp settings. Never saw a code like that, and replacement rear control unit (from a junkyard) fixed that issue completely. I used to get occasional balky vent code stuff on my 2000 A6, but since system worked in general I just tried to clear and move on. Again, no secondary code about control bus and had no obvious connection to general cooling effectiveness either.

wizardofoddd

got the a/c charged. it's now holding vent temps of 40 degrees even when the ambient temp is 77 or so. not the coldest a/c i've ever experienced, but it will do. thanks for the help

Panelhead