Knock/Click in dash

Post by **tom39** » 09 May 2010, 09:46

Recently I my 98 S70 has developed a clicking or knocking sound within the dash. It is not a rattle or sound caused by something loose. It sounds like an actuator trying to engage. I think it has something to do with the heat/AC. I say this because if I were to adjust the settings the sound changes.
Is there an actuator that controls the vent settings or degree settings that would be making this sound.
Note that the heat and AC work just fine and there is no issues in using them or adjusting the settings.

Thanks
TOM G.

JohnInFlorida · Post by **JohnInFlorida** » 09 May 2010, 09:57

I have the same sound in my 2000 Volvo S70 but I don't know what it is either.

Post by **jblackburn** » 09 May 2010, 10:16

Is there an actuator that controls the vent settings or degree settings that would be making this sound

Yes. I'm glad to know my S70 isn't the only one making these sounds, but wow it's annoying.

Behind the right (passenger) panel to the center console is the actuator/controller for the damper flap that controls the airflow between the heater core and the AC evaporator. You can either clean the contacts on this motor, clean anything it's "catching" on, or just replace it altogether ($$$, but the highest probability that it will shut up).

See the instructions for a heater core repair; the removal of the side panels is very similar. It's really not very complicated, I just need to make the time to do it.

Post by **tom39** » 09 May 2010, 12:55

Thanks for the info. Will give that a try. I had been turning the radio up to drowned it out. Be nice to not have to do that anymore.

TOM G.

Post by **Ozark Lee** » 09 May 2010, 18:50

You may very well have a split shaft on either the mode damper or the temperature dampers. There are several methods that our members have used to repair the shaft. There are a number of relevant postings in this thread.

https://www.matthewsvolvosite.com/catego ... e-control/

...Lee

Post by **tom39** » 20 Sep 2010, 17:31

Ok,I know it has been awhile but I just got to attempting to fix this problem. Now I have another dilemma, I took the glove box, radio, kick panels off and the clicking went away. I have been riding around like this for 4 days now and not a sound. For months this thing has been sending morse code like a cry for help and when I finally get there, NOTHING!!!!
Can someone point me to the common problem? Gotta start somewhere but I am not looking fro a wild goose hunt.
I looked at the link provided but not sure where to start if I can't pinpoint the noise.

Thanks
TOM G.

note4shawn · Post by **note4shawn** » 22 Sep 2010, 09:43

I too have the same knock. I have determined that it is temperature sensitive. It only happens when the interior cab is warm. It happens most with acceleration while turning although any acceleration or deceleration makes it knock. The harder the accel or decel the louder the knock. It always happens on warm days but never on cold. If it is cold when I start driving then have the heater warm the interior it will start knocking at a certain temp. I tend to think that it is a bushing or dash bolt that somehow is affected by heat expansion. To me it almost sounds like where the dash is attached to the body. This would make sense since it happens more while turning and accelerating because of the slight twist of the body/cab. I can kinda change how it acts by pressing/pulling on the windshield vent cover/dash that goes across the entire dash right at the windshield.

I am almost to the point of taking it in to a Volvo shop and paying a ton of money to get it fixed. It is starting to piss me off

I hope someone on here has figured this out.

Post by **Ozark Lee** » 22 Sep 2010, 18:59

Look at the temperature damper flaps and their motors that are mounted low on both sides of the climate unit.

...Lee

Post by **tom39** » 27 Sep 2010, 07:08

OK, both flaps and motors for the climate control appear to be functioning as they should. I have confirmed this by, removing both motors and checked their function, noting that the motors rotate according to the input of the climate control. I have also checked the function of both flaps and can manually move both freely in either direction, changing the temperature from hot to cold.

I also have checked the fresh air input is clear and appears to be operating correctly and the cabin filter is clean and cavity is clear of any obstruction. Only note of possible defect: The motion of the motor going from recirculate to fresh air is jerky, but the motion going from fresh to recirculate is smooth. Note that the flap fully engages in both directions.

Lastly, I have checked the function of the air flow selector. It moves from floor to dash to defrost and to the mix combination without any issues. The motor appears to be working as it should and the cog and arm to the flaps is unrestricted and moving freely.

I am at my wits end. This thing is baffling. The knocking sound is gone completely and the system works flawlessly in the garage. Now the issue that has reared its head is that after driving for about 45min to and hour it acts as if something in the system closes up and air movement is blocked somehow. The fan revs at full speed but the air movement slows to almost nothing. I have also noticed that when this happens the air is cool but humid. I do not smell any coolant nor am I losing any from the system plus the heater core was changed out last fall.

The service manage at the dealer posed the question of maybe the foam used around the heater core came lose and has been blown in the system and causing the issue. It is possible but I am not sure how it would block the flow of air completely, as it is a dual zone system.

Any and all thoughts would be appreciated.

TOM G.

Post by **tom39** » 27 Sep 2010, 07:15

Here is the schematic of the climate control system the Volvo Dealer printed out for me. Its not the best but gives a general idea of how it supposed to work.