1998 S70 Auto HVAC is going crazy, suddenly blows full hot

Post by **clarkerussell** » 11 Sep 2023, 11:27

Hello all, the automatic HVAC controls on my 1998 S70 is getting a mind of it's own. When on "auto", it will randomly redirect the vents, change from cold to hot, and the fan will increase to full speed. If I move it off auto, it goes back to normal. The lights on the display are NOT blinking...

Any suggestions on where to start?

Post by **clarkerussell** » 11 Sep 2023, 13:50

Well, in digging through old posts, I found MY OWN post from 4 YEARS ago... I'm an idiot...

viewtopic.php?t=89511

I'm going to update in that thread, butI am still having the issue after cleaning the interior temp sensor. And the "surging" of the fan is not the fan motor failing, but more like the HVAC controls changing it to high speed like it was trying to defrost or something.

V50M66 · Post by **V50M66** » 11 Sep 2023, 15:07

Get the 850 OBD2 app and a cheap Bluetooth OBD2 dongle and view live data for the ECC parameters. You should see pretty quickly what’s wrong. You can also try a new sun sensor, as well as a new ECC unit if you want to throw parts at it. I have both if you decide you want to try it, shoot me a PM

Post by **clarkerussell** » 11 Sep 2023, 17:17

V50M66 wrote: ↑11 Sep 2023, 15:07 Get the 850 OBD2 app and a cheap Bluetooth OBD2 dongle and view live data for the ECC parameters. You should see pretty quickly what’s wrong. You can also try a new sun sensor, as well as a new ECC unit if you want to throw parts at it. I have both if you decide you want to try it, shoot me a PM

How am I just now learning of this App?!?!? I just installed it, dusted off my never used BT OBD2 dongle, and pulled some data. I need to figure out how to interpret the the log, but at least I have it! Thank you!

V50M66 · Post by **V50M66** » 12 Sep 2023, 06:26

clarkerussell wrote: ↑11 Sep 2023, 17:17
V50M66 wrote: ↑11 Sep 2023, 15:07 Get the 850 OBD2 app and a cheap Bluetooth OBD2 dongle and view live data for the ECC parameters. You should see pretty quickly what’s wrong. You can also try a new sun sensor, as well as a new ECC unit if you want to throw parts at it. I have both if you decide you want to try it, shoot me a PM
How am I just now learning of this App?!?!? I just installed it, dusted off my never used BT OBD2 dongle, and pulled some data. I need to figure out how to interpret the the log, but at least I have it! Thank you!

Go to live data, click up top where it says ECU. Then choose ECC. It should then show you all the climate control parameters (car must be running) - alternator D+ signal, blend door states, fan speed, sun sensor reading, etc. If one number is jumping around, try replacing that part first

Post by **clarkerussell** » 14 Sep 2023, 17:17

OK, so I bought a new BT OBD2 reader because mine wouldn't pull live data. I have it now and I'm getting some off readings on the EC report.

: Screenshot_20230914_182830_850 OBD-II.jpg (116.6 KiB) Viewed 541 times

The AC button shows off, but it was on.

Engine temp is showing 76.71 degrees, but it was at full temp (showed about 190 in the COMBI field).

Air Distribution damper is at 200%, I'm assuming that's the one that's been making the groaning noise for years...

Sun sensor value dropped as I covered it, so I'm assuming it works OK.

Cabin temp bairly fluctuated (less than 1 degree)

Based on these results, does anyone have a recommendation on what to do? Should I swap the ECC?

V50M66 · Post by **V50M66** » 15 Sep 2023, 08:34

Swapping the ECC unit is a good starting point. Keep in mind, they are '98 specific - even though they look the same, a '99 module will not work and cause the whole electrical system to freak out. You need part no. 9171595 (or it's revision), NOT 9171800. Make sure to double check with eBay sellers or verify the car is a '98 if harvesting yourself at the yard.

I do have a working '98 ECC if you need one, though it is in mediocre condition and (if I remember correctly) stuck in relearn. You can kick it out of relearn manually in the app, and then it will work fine, but it's not the prettiest. Message me if you're interested.

Post by **abscate** » 16 Sep 2023, 02:51

If I can find my good 1998 ECC controller I’ll send it down. Pm me your address

I’m rehousing all parts that have resided 5 years o r more so I don’t end up like that guy in Calgary

Post by **scot850** » 16 Sep 2023, 05:57

Not sure who you are talking about................??

Neil

Post by **clarkerussell** » 11 Oct 2023, 20:59

So I was at a pull-a-part yard and they had a 1998 S70 with ECC so I pulled it. The sticker on the box shows 9134784. @V50M66, you said I need to look for 9171595, is the 9134784 not compatible?