Air Only Blows to the Windshield - Hot or Cold

[songzunhuang]

850's used to have a motor on that end. There is one on the driver's side that turns that shaft. The black item behind that is a servo motor so you are correct in your assumption. If you remove it (I can't recall the size of Torx screw, T15 or 20? It is not 'fun' extricating that motor as you need to be bendy and it is hard to see the screws. A mirror on a tick with a built in light may help. I can't now recall if I used a bendy stick with a Torx bit on it to get into the screws. Last did that a long time ago.

Once you have the motor out, mark the position of the motor shaft flats to the motor case so if you try to test it with a 9V battery, you can make sure you get it back to the correct position before re-installing.

Neil.

So I used my handy dandy boroscope to see where the screws are. I was hoping to get more definite info on the problem before I dig that damper out.

I did take apart the ECC just to clean up the connections if needed, but I really can't say that looked bad.
Here's the front side.

Front side with components

ECC Front.png (2.19 MiB) Viewed 382 times

The backside.

Back side with solder joints

ECC Back.png (2.75 MiB) Viewed 382 times

I cleaned it up and put it back in. There are no error code lights happening.
I did hear that tapping sound once again. I noticed that when I turned the knob to direct airflow from the windshield to the front vents or the floor, the tapping sound would stop. However, the airflow didn't seem to change. I am still getting air at the windshield, but this time, I also feel a flow from the front vents.

I really suspect a bad motor or sensor in the suspect motor. I just don't know which one. According to a previous post, it may be one under the driver kick panel. The sound seems so clear coming from the center of the dash (where the flaps are?). When I have a day of tinkering available, I'll take a look at the motors under the driver kick panel. I'm just not so sure what I'm looking for!

I also bought a replacement ECC on eBay, but I fear that's not going to anything. Oh well, more spare parts.

[FireFox31]

Of the two dampers on the driver side, do you know which controls the windshield / front vent direction?

According to my notes, the one being pointed to does the vents and floor/defrost on a 1999 and later. Supposedly, the 1998 has a motor on the passenger's side for floor/defrost (as shown in the 850 diagram I linked), but yours doesn't have one. Perhaps the one being pointed to was combined to do vent/floor/defrost in 1998, not 1999. It might be reasonably easy to remove that motor and watch it try to work while still connected to the car.

[songzunhuang]

I came across this official looking document that has some great information about my ECC unit and other things about our cars as well.

https://automotivetechinfo.com/wp-conte ... r-2018.pdf

It confirms that I only have 4 dampers. It also states a procedure to auto calibrate if I were to replace the damper motor (which I think I am on my way to doing). Anyhow, came across this and thought I would share.

[songzunhuang]

In the interest of sharing accurate information, in another thread, the author has the same issue I have and indicated that the damper in question is the one pointed at by the arrow below.

Motor for defrost / vent control.

HVAC-Box2-jpeg-600×800-.png (1.19 MiB) Viewed 298 times

Note this picture was borrowed from an eBay seller who listed the HVAC box for sale.

However, the problem according to him isn't a motor issue. He has observed that the black plastic end that the square motor shaft is inserted into has become messed up and is no longer square. Basically it's rounded off so the motor shaft cannot get purchase. This makes sense to me and I'll investigate further. The damper motor has to be removed to see this black plastic shaft end.

The trick is to do this without having to remove the entire dash and/or the white HVAC assembly. That's a very time consuming job.

[scot850]

There is a 2nd thread with this same issue.

I had an issue with one of the P80's I had. When I opened the box, what I found was the rubber type seals on the flap had gone soft and sticky to the point the flap had stuck. I'm guessing the torque of the motor was sufficient to damage the square section.

Repairing the the square section had really only one option and as Abscate say sit is a while dash pull and removing the box to replace the flap. Not sure if the flap is even still available.

Neil.