Question about climate control unit. B6 vs B7?

[BASARAB]

First of all, ECS must be on crack http://www.ecstuning.com/Audi-B6_S4-...trol/ES438111/.
But anyways, I just have ordered a b7 unit with part number 8E0820043AM, my original unit 8E0820043AD. Should I install a new unit or should I just swap the front plate? Units look exactly the same, but if I am not mistaking I remember reading somewhere, that b7 unit wont operate properly in b6 even if it correctly recoded.
Does anybody have first hand experience with that?

[onceover]

Why not just try it and see if it works?

[BASARAB]

Why not just try it and see if it works?

Cause I just have ordered it today, but want to find out sooner than it arrives

[FoRbAnNa]

Am I missing something here? Is $1005 a bargin? Or did the price just go up? I paid $500 for a new ac last year and I thought that was expensive even though dealer wanted $1695..

If you can manage without a rear defroster and always have the leds on the ac unit run at full lumination and won't mind 3-5 codes then yes it would work. I think there are some later B6's that can use B7 ac units but the early models def can't without having issues like I just said, ask me how I know.. I ended up swapping the front on my new 2DIN B7 unit over on my 1DIN B6 unit when I did my 1DIN to 2DIN dash conversion last year. Hot and cold air works fine but the rear defroster light would go out in less than a second after pushing the button. After what I found out the B6 uses a built in relay to control the power to the rear defroster but the B7 units have the relay somewhere else in the dash, not built in the ac unit and therefore a B7 unit won't work in a B6.. Also the lumination on the led display was running at it's strongest all the time and I always had like 1-5 different codes related to the B7 AC unit not working properly in my B6.

[FoRbAnNa]

The unit in your ecs link, rev AG works in B6 A4 and S4 but the AM rev you said you ordered is an outdated B7 model that later was replaced by the BM rev. Which is what I bought that didn't work that well as I described above.. My original ac unit had the A rev, later replaced by both J and now AB. Going from A to BM didn't work so I suppose you would also have the same problems as I did. Here are some of the codes I got after installing a B7 ac unit in my B6:

18043 - Powertrain Data Bus: Missing Message from A/C Controller
P1635 - 35-10 - - - Intermittent
00975 - Heated Rear Window (Z1)
39-00 - Output won't Switch or Short to Ground
01794 - Control Module - Incorrect Chassis (VIN) Number
35-00 - -
01320 - Control Module for Climatronic (J255)
49-10 - No Communications - Intermittent

[BASARAB]

Lol I am not buying ECS unit, that price is just an error I believe, MSRP for this unit is about $500. I ordered a unit from a salvage yard for $50. I keep researching about it and somebody mentioned a resistor fix for rear defroster, however I cant find anymore info about it

[BASARAB]

Got the new unit today, its actually BM version. Will install and report back after my fever goes away and I can get out from the house. Its very nice to see that nothing is peeling on new unit lol

[BASARAB]

For those who will have the same question. As Forbanna posted b7 unit works in b6, but rear defroster will turn off right away

[FoRbAnNa]

Have you checked for codes after the install? Got the same codes as I did?

[BASARAB]

Nope, I did not check the codes, I basically just ran out to check if it works. Still got fever and its too damn cold outside lol

[DPDISXR4Ti]

If you can manage without a rear defroster and always have the leds on the ac unit run at full lumination and won't mind 3-5 codes then yes it would work. I think there are some later B6's that can use B7 ac units but the early models def can't without having issues like I just said, ask me how I know.. I ended up swapping the front on my new 2DIN B7 unit over on my 1DIN B6 unit when I did my 1DIN to 2DIN dash conversion last year. Hot and cold air works fine but the rear defroster light would go out in less than a second after pushing the button. After what I found out the B6 uses a built in relay to control the power to the rear defroster but the B7 units have the relay somewhere else in the dash, not built in the ac unit and therefore a B7 unit won't work in a B6.. Also the lumination on the led display was running at it's strongest all the time and I always had like 1-5 different codes related to the B7 AC unit not working properly in my B6.

I went searching for the thread about swapping in a B7 HVAC control unit into my B6, but I just stumbled across this comment above which is causing me to stop in my tracks. I have an early (12/01) 2002, and had been thinking the B7 control unit (8E0 820 043 BM) was mostly plug-n-play, save for adding a circuit for the "off" button not found on my original unit. Can someone shed some further light on this situation? Is there a build-date cut-off that defines "early B6" for the purposes of this topic? I'm assuming mine qualifies as "early".

[frenchyofcp]

Has anyone figured out how to run a B7 CC unit successfully?

[Charles.waite]

I ran a b7 one in my b6. All I needed to do was to rewire the rear defroster through a relay. Matt Devo has a really good DIY for that. Not sure what everyone is talking about codes, but the b7 one worked great in my 2004 b6.

[EuroxS4]

As mentioned the only difference was you need to add a relay for the rear defroster at the ac head. There is a good DIY floating around somewhere IIRC.

[DPDISXR4Ti]

Ignore my comments a couple posts up ^^^ from 2019, as I was all screwed up in my thinking at the time. I'm currently running a late B6 unit in my early B6, and it was 100% plug-n-play; no need to add anything to enable the on/off button found on the late B6 units.

What I don't know however is if there is an issue putting a B7 unit in an EARLY B6. I know about adding the relay for the rear defroster as discussed in Matt's write-up, but is there any validity to what I quoted above from FoRbAnNa?

[DPDISXR4Ti]

Here is the link to Matt's thorough write-up....
https://www.audizine.com/forum/showt...ight=defroster

There's no mention there of any difference between early and late B6 models when doing the B7 swap. I'm classifying that "info" as sketchy, at best.

[EuroxS4]

No you can adapt the ac head and it should be free of codes. I have yet to see anyone have issues. I have a b7 ac head in one of my b6 a4 from 2003 model year. As long as you adapt to the vin you should be good to go.

[frenchyofcp]

Awesome, thank you guys! Going in my 04 USP.