2000 S70 passenger side stuck on heat

itsmekirby · Post by **itsmekirby** » 01 Nov 2023, 19:30

I've read a few threads about this issue but wanted to see if anyone has advice specific to some particular symptoms I've noticed.

2000 S70 GLT SE with an electronic climate control unit. The mode knob and the passenger temperature knob stopped working at about the same time - it is stuck on defrost+front vent mode and full heat on the passenger side. The drivers side temperature knob works normally. The passenger side only puts out heat from both the defrost vents and the front vents. No air on the feet vents. No flashing lights or other unusual behavior from the control unit.

This started during a cold weather trip so, while the two knobs failing at the same time feels symptomatic, my guess is the weather made both damper spines brittle which caused them to fail simultaneously.

One other symptom I noticed is that the passenger temperature did briefly work during particularly cold mornings. My only explanation for this is that it stiffened the plastic in the damper controls enough to get it to barely work.

Anyone have any advice? Agree or disagree with my diagnosis? I'm ok with hack solutions if they're easier, and do have access to salvage yard parts.

Post by **abscate** » 02 Nov 2023, 03:26

Do your ECC controller unit lights for recirc and AC flash for a few seconds on startup? That tells you ECC codes are stored. If it doesn’t , I would guess the passenger side gear linkage to the damper has fallen off

I think you can get to it easily after removing the glove box

I’ll try and find pictures

itsmekirby · Post by **itsmekirby** » 02 Nov 2023, 09:08

No flashing lights. And that would be great thank you!

Post by **scot850** » 02 Nov 2023, 12:20

There are many threads on heating system issues. I think you may have more than one issue, and the fact you are not getting codes may be a symptom of you ECC unit failing. There are too many issues from your list to believe that you would have multiple failures all at once.
If you decide to swap the ECC with a junkyard item, make sure it is from a 99-00 model. 98 is different operation internally.

I would look at removing and cleaning your cabin temp sensor. I did a thread on this a while back on how to remove and clean it. It requires radio removal (make sure you have the code), ECC control unit removal and then you can access the temperature sensor to the left of the ECC unit behind the dash. If you look at the RH end of your dash buttons nearest the ECC unit you will see a small grill. The temp sensor is behind there.

You can also check the cold air flap lever has not broken which will only let warm air in.

There is also a rotating knob to the left of the 2 center dash air vents. This increases the amount of fresh air into the cabin. In summer you want that open, in winter closed.

Servo motors (4 off) can fail and there is a possibility flaps can stick internal to the air control system or they can break.

I would suggest finding a way to have your ECC system scanned for issues even if it is not flashing to make sure the system has no codes that could help identify issues.

Neil.

itsmekirby · Post by **itsmekirby** » 13 Dec 2023, 16:09

Finally got around to pulling the damper motor behind the glovebox to find that 1) the motor seems to be functioning normally (it moves in response to the passenger side temperature knob with good force) and 2) that the spindle it plugs into feels intact. I can twist the spindle a little with my fingers and it feels the way I expect (I can twist it one way but not the other since it lays against a stop, and when I release it pulls back to that stop by gravity I guess). I took a photo and see no cracks in the spindle.

So at this point I'm stumped because I feel like I've ruled out an electronic issue by the first observation and a mechanical issue by the second observation. My gut still says there must be something wrong with this motor-spindle connection that I'm just not seeing. What do you think?

V50M66 · Post by **V50M66** » 13 Dec 2023, 22:54

Odd. It's possible that it's cracked internally. Also, verify your motor and spindle are clocked correctly in relation to one another. If it's not, it will try to force the door past its stops and blow the spindle apart.

V50M66 · Post by **V50M66** » 13 Dec 2023, 22:54

V50M66 wrote: ↑13 Dec 2023, 22:54 Odd. It's possible that it's cracked internally. Also, verify your motor and spindle are clocked correctly in relation to one another. If it's not, it will try to force the door past its stops and blow the spindle apart and/or just refuse to work because it's encountering too much force at the wrong end of the travel

Post by **scot850** » 13 Dec 2023, 23:36

The flaps can degrade and become sticky and actually stick to the casing. Try to move the spindle yourself. Careful use of a small flat blade screw driver on a diagonal may work to try to turn it unless you have a small square bar to fit the hole. If using a screwdriver to not force it or you could crack the spindle end.

Neil