ok I have very little air moving to windshield under defroster mode. I removed glove box and removed servo and operated by hand I CAN SEE WHY THE SERVO GO BAD hard to turn agasint blower force anyway doesn't help at all doing by hand. 95% is blowing out vents. Both yellow lights flash on cimate control when veh. is turned on. Then flashing stops. I cannot get air directed to windshield no matter what I do. What other damper servo controls windshield defrosters or do I have a control problem???

 

Anybody ??? any schematics on air box anywhere anybody and prints.???? on door system and servos ????

 

the flashing lights are the climate control computer telling you there is a fault code. Check out volvotips.com to see if you can pull the codes from the OBD1 LED box. There are something like 5 servo motors controlling the air blend doors - it sounds like the one opening to the defroster is either out of sync or bad.

 

what is the one behind the glove compartment suppose to be doing

 

https://www.matthewsvolvosite.com/fo...ic.php?t=48265

There's a passenger's side temperature servo and also the defroster servo.

Volvo 850 ECC climate control AC & heater system service manual


Since you are in there anyway, can you tell whether or not that damper does what you think it does? I don't know whether the ventilation damper has to be in a certain position for the defroster to work, but I would guess not. It's probably just open/closed going to the dash vents. if that's true then it needs to close. If the air is coming out the vents when you want defrost, then in fact the dash vent servo failing is the actual problem.

 

OK so far I found that it takes two of the servos to control volume of air to point to the windshield IE defrost, one is the glove box defrost servo and also the ventilation damper drivers side main one, with the two exterior half gears. It seems shaft is split on defrost servo making that one inoperative and the servo with the two half gears jumped out of time and no longer mesh with each other forcing that one to be in vent mode all the time. drivers side is a back breaker for sure. Easy way to tell is on glove box side you have the other end of shaft RED looking **** and its free to spin letting you know its not coupled to servo anymore on the other end drivers side.

 

Theres no description anywhere describing the correct operation of the defrost mode. Not anywhere.

 

You have to check these shaft with no blower motor going as you are fighting the air pressure and cant turn with your fingers

 

So as a emergency procedure you can clamp a small pair of vise grips to red **** being careful not to crush plastic and get some air direction to the windshield, of course you have to leave glove box out. Taking off servo on defrost shaft I temp. pushed a long rubber hose over shaft and can twist that one as well.This one also controls vent to drivers and pass. feet with air.

 

I would gather that the grease slobbered up the carbon wipers on the variable switch and thru servo out of time. I did find that on my own and then seen it on the web so I was spot on that baby.

 

Just the other day I replaced the dash lights dimmer switch and then tore the old one apart to find that it was burnt and broken on the carbon track. The electronics was ok just the mechcanical carbon slide failed. 10 min. job.

 

Thanks for the info that way mighty nice of you.

 

The fifth one is outside or inside air only there are really 4 that control in the car air blending and defrost take two of them to get the job done. Both of mine were bad. If the servos are fixable because of the grease and get back into time then ecc should become clear then.

 

So you figured it out? Great! Hope you can find some parts. I sure don't like working on them. Need to be a contortionist.

 

Contortionist for sure, good think I am trim and fit yet. Yes this will be a time for making creative tools. Still hard on a 68 year old. I like my race car better easier to work on lmao.