[97 850 w/ECC] Front Vents/Defroster Mix

[mercuric]

Hi all,

Having lots of fun today going over the ECC system in my new-to-me 97 850T5. Evil contraption!

Right now: Vent controls (the round knob) do nothing. It's stuck on half-front vents, half defroster. Evil blinky lights. Haven't read codes, hoping to not care about them.

Goal: Get it on front vents only. Everything else is optional, and probably more trouble than it's worth. Just give me cold AC in the face... It doesn't get cold in Texas

Did a bunch of reading and found the split damper shaft (behind the glovebox) issue. Disassemble glove box and remove motor, yup, shaft is split.

But it seems that shaft only controls the mix between the upper vents and the floor vents? I can turn it by hand, when I do, it goes between all air to the floor at one extreme and the half-front-vents, half-defrost setting (with floor vents closed) at the other extreme. It doesn't turn very far, less than a 1/4 turn.

So, is there another motor/damper combo that controls the mix between the front vents and the defrost vents? Or maybe closes/opens the pathway to defrost? If so, where do I find that beast?

OR, should that split shaft turn further, such that if it kept going, it'd direct all air to the front vents?

Thanks!!

[mercuric]

In the hunt for more ECC info, I found some stuffs...

component locations


ECC
- Damper motor, driver's side (16).
- Damper motor, passenger side (17).
- Damper motor, recirculation (18). Ulike the MCC recirculation motor, this has stepless control.
- Damper motor, ventilation (14).
- Damper motor, floor defroster (15).
- Power stage (11) controls fan (12) speed. As the power stage generates a certain amount of heat, the cooling fins face inwards towards the airflow.
- A/C relay (13).

MCC
- Fan resistance (1).
- Max. fan speed relay (2).
- A/C relay (13).
- The recirculation motor (3) controls the recirculation damper in two positions in versions without A/C (open/closed), and in three positions in versions with A/C: open, closed or 30% recirculation at max. fan speed.

15 "Damper motor, floor defroster" seems to be the motor connected to the split shaft some of us have encountered.

The wiring diagram of the ECC unit has verbage with some more information (first imaged linked for full view, if you so desire)




So it seems the 16 and 17, the drivers and passenger side motors, are for temperature control. 18 is of course recirc, leaving 14 "Ventilation shutter"... Still not sure what the intent of that one is, exactly. Suppose I should dig for it, guess it's on the drivers side?

Info hunt continues

[mercuric]

Video, damper motor testing:


I didn't have a 9V battery, but did find a 9V wall wart in the bin 'o random old wall warts, rated 500ma, and that worked just fine.

Mark the gear with a sharpie or whiteout before, so you can spin it back where it was.

Like many others, I also found the white lithium grease had migrated to the contacts under the gear, which needed to be cleaned up of course.

[mercuric]

Huhm... This ECC system is way too smart for my liking. Generally, when one selects the icon for "front facing vents" on the selector, one expects.. front facing vents. Not so much with ECC. Hate it already, but here's how it goes:

From http://www.volvoclub.org.uk/tech/servic ... m-Auto.pdf
(plenty of good info in this doc)



Yup, it's a wiseguy. I'm the wiseguy, not you, car !

With the above info, I was able to get it to vary the distribution between front vents and defrost vents by varying the temperature control between extremes, so I guess the ventilation control motor isn't totally borked. Good! although it still sends some air up the defrost and the side vents (far passenger/driver) blow very little whereas the center vents blow much more. Hmm. At this point, I suspect all the other damper motors have lithium grease on their sensor contacts, the ECC computer has no clue what's going on, and I need to clean them all. I'd also suspect the computer lost track of the floor/defrost damper motor position (and probably the other ones too!), leading to it overrunning the position and splitting the shaft after it whacked on it a sufficient number of times. Age and texas heat has made all the plastic brittle -- For example, when I disassembled the floor/defrost damper motor, the tabs cracked as soon as I put enough pressure on them to move them at all. There are several recommendations on how to fix the shaft linkage on this site, including sleeving the split shaft as well as extending the damper motor shaft by various methods to fit further into the damaged shaft. Hopefully I'll find some time to monkey with that soonish, as well as getting to all the other motors. I read here the calibration process is an absolute PIA... I'm going to forget I read that and worry about that later.

Maybe I'll get this working as designed after all, depending on my patience level and willingness to dig into the dash innards.

I guess I've answered most my own questions so far, but I'm going to keep posting any info I find, and let you all know how this little nightmare goes, hopefully you will learn something and/or have a good time laughing at me

[jreed]

Hi Mercuric--
Great posts! Thanks for uploading the documents.
I had similar problems with the ECC unit on my car last year and I found the code reader to be a handy little gizmo for shedding light on what the ECC is complaining about.
The code reader is not too bad of a DIY... all you really need is some wire, resistor, LED and a switch. If you don't already have these parts lying around as spares, you could get them from Radio Shack or some other electronic supply house (like DigiKey) for small money.
I wrote up a short guide on the code reader here:
https://www.matthewsvolvosite.com/forums ... 43#p251189

My adventure fixing pieces of the system is here:
https://www.matthewsvolvosite.com/forums ... 5&p=251436
and here:
https://www.matthewsvolvosite.com/forums ... 8&p=254621

[mercuric]

Thanks, jreed! Great posts also. Looks like you tore down the motor further than I did, I should probably remove the board as well and clean up the underside -- I just did the board and contacts under the large plastic gear.

Right now I'm thinking I'm going to try to extend the shaft of the damper motor... There's a post that shows one creative forum member using some spare bits to extend the damper motor shaft further into that evil plastic shaft that likes to break.

https://www.matthewsvolvosite.com/forums ... 6&p=102794

The third pic, with comment "As you can see, there's an opening in the base of that plastic part, and it is much stronger than the rest" got me thinking this is the right way to approach this repair. I like how you think, sir Marginal

He comments further on that opening further down in reply to his own thread:
"The parts that were still on (2 out of 4 walls of the square plastic opening) were soooooooo very much loose, that I decided to just brake them and take them off.
The remaining opening is on the contrary very strong."

Good, because what's left of my shaft is like his.. Partial and is certain to break the rest of the way.

The damper motor shaft, according to my best measurements using a (janky old) manual caliper, is exactly 3/16", and with part of the end of the plastic shaft completely trashed, I'm going to try to sleeve the damper motor shaft with a stub of 3/16" ID (inner diameter) brass square tubing into which I can slip a longer piece of 3/16" OD square brass. Should only need 1/4" to mate. Solder-bond the brass sections after adjustment, then epoxy the "extender" onto the motor shaft... Seems like the most solid way I can think of. K&S engineering makes the exact tubing I'm looking for, hopefully the local hobby shop has it in stock (fat chance, since I could use it, lol).

Update: So indeed the local Hobbytown USA had the goods, K&S stock number 153 (3/16th OD) and 154 (7/32nds OD). The 3/16th slides nicely into the plastic tube, but the 7/32nds is just a hair too small to fit over the damper motor's stubby shaft. I suspect the dimensions are actually metric. However, when I get home (stuck at work now) I suspect a little dremel action on the motor shaft to remove a few hundredths will result in a purrr-fect press fit, so maybe that's for the best. Probably better than trying to bond a loose fit to the stub shaft. Note that for this to work I'm planning on carefully removing about 1/2" of the remaining split plastic shaft, such that I can extend the motor shaft with 7/32 tube and then fit enough 3/16 tube to fill the entire shaft. Getting the length of the 3/16th section will be the trick, as will be removing some of the split shaft. I think it's doable though. We'll see.

They also had some 7/16th OD brass round tube, which has an ID of a little over 10mm, I need to cut it to try it (should have brought the dremel with me!) but I think it should fit over the plastic shaft. I'm going to cut a section of it about 1/2" long and epoxy it around the inner end of the brittle plastic tube in an effort to prevent it from cracking -- a sleeve. It might be a little big (calculated ID is 10.4 and I read the shaft is 10mm) but that's nothing a wrap of tape won't fix, and again that should result in a press fit.

The three 12" sections of tube came to about $8 w/ tax.

[mercuric]

Well awesome. My above-mentioned plan seemed to work out pretty nice.

First, I cut two pieces of square tubing.. 5/8" length of the 7/32" OD, 7/8" length of the 3/16" OD. These interlocked to form a little thing:


The dimensions were too long, as I'd find out by several rounds of trial and error, but that's OK. Easy to buzz down with the dremel. I then ground down the motor shaft until the wider tubing press fitted on.. The next picture shows the final deal, after finicking with the length to get it seated properly in the plastic shaft. The final dimensions were about 15/32" for the wider piece that slips over the motor shaft, and 5/8" for the narrower piece that fits into the plastic shaft. If you're going to re-create this, I recommend you start with the dimensions I did and cut a little bit off a few times until it seats as far in the plastic shaft as you can get, while the wider piece attached to the motor clears what's left of the plastic shaft.



Then, I cut a 1/4" legnth section of the 7/16" OD round tubing


Which was the right length, but a little too big around, so it was somewhat loose on the shaft. So I wrapped 1.5 turns of electrical tape cut down to about 1/4" width and jammed the brass "sleeve" over the shaft in hopes of making it less likely to split in the future. Then, I cut off what was left of the plastic shaft, which resulted in:



Which I cleaned up a bit after taking the pics, but you get the idea.

After adjusting the length of the rods to get it just right, I put in two of the screws and used some jumper leads to see what'd happen, and it happily opens and closes the damper now. Win!

You have to cut off what's left of the split shaft to use this method, as I did, because the remainder will interfere with the new, wider bottom part of the extended motor shaft. But that was the broke part anyways. I guess if it's just partially cracked, the method of simply sleeveing it will probably do for you, but in my case the other half of the shaft had fallen off and was probably vacuumed up long ago by the previous owner.

When you grind down the damper motor shaft, take off a little bit at a time using a grinding bit until you get a good press fit. You don't want to overdo it, or it'll fit loose. You don't have to grind off much.

Use a pair of vise grips or similar instrument, and bend in the walls of the wider piece of square tubing that goes on the motor shaft, at the end opposite the motor shaft. Just enough to make the narrower tube press fit into the wider one. This way it stays in place and won't come off in the shaft when you remove the motor again.

Parts: K&S Precision Metals stock numbers 153 (3/16" brass square 12" long), 154 (7/32" brass square 12" long), and 137 (7/16" brass round, 12" long). You can find these at most Hobbytown USA or Jerry's Artarama retail shops, among many places online (google is your friend).

Now to get at the other damper motors, clean them up, and see what other nastiness I have to fix. Then the nightmare of trying to calibrate the system. I think I'm done with this project for a few days. I know the recirc damper works fine, the ventilation damper seems to work at least partially... Which reminds me, I forgot to try the heat when the car was warm earlier.. drat!

[jreed]

Nice close-up photos! They are among the best I've seen.
Thanks for sharing this fix. I admire your enthusiasm and energy... I'm looking forward to your contributions to the site!

[mercuric]

Nice close-up photos! They are among the best I've seen.
Thanks for sharing this fix. I admire your enthusiasm and energy... I'm looking forward to your contributions to the site!

Cheers! Glad I could share something I really dig macro photography, fun stuff.

[combatkarl]

Hey everyone,
Trying to fix my issue with ECC and no heat or defrost. My problem is similar to Mercuric's issue, except where Mercuric has room on the plastic shaft for the brass "sleeve" my shaft is broken almost flush with the it's mounting area. If looking at the last picture on Mercuric post, the shaft would be broken behind the brass "sleeve." I'm hoping to recreate the square tubing shaft, but mine might be longer. Anyone else have any other thoughts? I'm assuming to replace the broken shaft would mean removal of the entire dash?
Thanks
Karl