97 850 NA - Regular soft knocks/clicks -- repeated pattern of movement

Post by **xHeart** » 29 May 2018, 13:09

The moment key is inserted in to ignition, clicks or knocking sound is heard inside the dash. The pattern is repeated endlessly -- click click - pause - click click. It is a gentle sound of plastic object trying to engage. More towards the passenger -- kick board than the glove compartment.

I am suspecting, it has started to stress the battery.
Heater works fine, fan is great, but AC hasn't worked for two years.

TIA!

Post by **bmdubya1198** » 29 May 2018, 18:17

Weird... that location of the noise would lead me to believe the blend door arms are the culprit, but that shouldn't do anything right when you insert the key.
I'd drop the kick panel and look around.

Post by **scot850** » 29 May 2018, 20:08

Check the servo motors in the heating system as suggested. Whilst not guaranteed in your case, that is what I had with a bad servo motor as it wasn't able to find its home position. It was the one on the RHS of the center section to the back in my case.

Neil.

Post by **xHeart** » 30 May 2018, 09:11

CORRECTION bmdubya: Not at inserting the key, rather at POSITION I & II.

#17 in this diagram is a motor. Does this motor controls shutter underneath the charcoal filter assembly?

Details here:
http://volvopartslisle.com/assembly/253 ... eater-Unit

Post by **scot850** » 30 May 2018, 10:36

Number # 17 is one of the motors. That controls the cold air intake and mounts to the side of the cabin fan housing. It should have a plastic rod that rotates and turns the flap behind the cabin fan motor and below the cabin filter.

Being an 850 there are 4 (?) more motors if I recall. There are 2 on the RHS of the center section. One where the arrow for #49 is pointed to and the other where #45 points to. The one at #45 goes into a plastic sleeve than can split open. You can try gluing it and then tightly wrapping a small zip-tie around the shaft to prevent it breaking again. You used to be able to buy a replacement part that could be replaced with an internal flap on that side of the center section. Not sure if it is still available.

The other 2 (?) motors are on the other side of the center section above your right knee.

Neil.

Post by **bmdubya1198** » 30 May 2018, 11:29

Gotcha, that makes more sense. Number 17 is for going between recirculation and fresh air. You could probably test that by turning recirc on and off and seeing if you hear the noise.
Otherwise, the other motors/arms are for changing the zones. So, you could rotate the knob to change between the main vents, the floor vents, defrost, etc. and see if the noise stops on any of those settings. Or if you notice that the zone of air flow doesn't change when going from one setting to another, especially on the passenger side, that could point to that arm being an issue.

Hopefully that made at least a little sense, I'm trying to figure out how to word it!

Post by **xHeart** » 30 May 2018, 14:45

It is the #17 motor. It stopped when switched from fresh air to recirculation. So at recirc it no longer clicks.

Thank you bmdubya and Neil.

Post by **bmdubya1198** » 30 May 2018, 15:53

Inspect the arm (#18). That's likely where your problem is.

Post by **scot850** » 30 May 2018, 16:27

It is the first thing that breaks that arm. It can still be bought new, or it was about a year ago.

Neil.

Post by **xHeart** » 30 May 2018, 16:41

Thanks Neil!
I'll check with Volvopartslisle, meanwhile eBay shows: