Working on a new to me '97 850 GLT with the electronic CCU. (198K miles)

After putting the temp. knobs to max cold, I am still getting some heat blowing from the vents. No warning lights on the ECC unit.
My last 850 had the manual climate control unit, which I believe had cables controlling the vent doors.
Where would y'all suggest looking at first to fix this.
Are these known to have bad servo/stepper motors, bad vent door seals ??

Thanks all.
Peter

If you get the orange blinking lights of death at engine start (the recirc and AC buttons have LED's in them), there will be one or more error codes stored in the ECC. You can make a code 'reader' with some wires and a 12V light bulb (LED is better):
https://www.matthewsvolvosite.com/forums/viewtopic.php?t=79406

I used large paper clips, straightened, to connect the 3 wires to the OBD box. The OBD is under the coin tray in front of the shifter.

If there are codes, write them all down, and then clear them. Unplug the 'reader' and restart the engine, then shut off the engine and check the codes again - these are the ones that you need to deal with.

The vent motors normally are very good and last forever. The plastic used to turn the vents is another story, they tend to crack and fail. The motors are all held in place with T15 screws, 3 of them. Only one, the ventilation damper motor on the driver's side gave me a problem - that one opens/closes the dash vents - and I had to remove the upper dash from the car to get at it.
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Keeping it running is better than buying new

Thanks for the info.
No ECC codes at present, so I will remove dash cover to see what's up with the vent motors.

The entire right side can be viewed by removing the glove box and the knee brace. Removing the dash cover is the last resort!

Did you check the AC lines going into the car from the engine bay? The low pressure one should be very cold and the return line should be cool to the touch. You may be a bit low on R143a, as are most 850's.

As for the vents, move the vent selector from one position to the next. Give it a couple of seconds to determine movement.

The blinking lights of death might not always show up unless the blower speed is in auto and the vent selector is in auto at start up.
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Keeping it running is better than buying new

The AC system had NO pressure, so I added 1 12oz can of Freon. This caused the compressor to cycle on & off constantly. I'll add another can to see what happens, I think the AC system takes 26oz of r134a.
The passenger side seemed to blow "slightly cool" air, the drivers side continued to blaze hot air.
So it would appear that the driver temp/vent door/motor is stuck.
So it's off with the dash top !
I'll double check for blinking ACC lights.

Thanks
Peter

I hope I am not too late!! The vent you want to look at is above and to the rear of the gas pedal. No need to take off the dash for this one. It just means working upside down in cramped space. I have been known to remove the seat bolts and flip the seat rearwards, just for better work room.
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Keeping it running is better than buying new

Nope ! not to late, thanks.
BUT, I did just get the "binking trouble lights" on the ECC, but only just once !
I'll get the codes after I make the "LED/switch" code reader.
I'll also get my head under the dash to check out the drivers side vent motor.

The dash top removal is no fun. The steering wheel has to come off.

Once off, it will become obvious that you are almost at the point where you can take the entire heater box out of the car and replace the evaporator!!! That is probably where your leak is anyway.

If you do remove the dash, get some good glue and use it to reinforce the T25 screw holes that hold the kick plates.

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Keeping it running is better than buying new