The everlasting HVAC problem

dsno · Post by **dsno** » 12 Sep 2017, 11:17

Good evening guys.

i've been searching and searching, and trying and trying. and looking and looking. starting to pull my hair soon.

i've got a 1999 Volvo V70 2.5TD which has some gremlins with the climate control.

the thing is. i'm freezing my balls off when it gets cold. there is little to no heat coming out of the vents.

the engine is warm as it should be. the heatercore heats up as it should. but i'm still freezing.

ECC panel works, no blinking LEDs.

but the wierd thing is. every once in a while i get a loud "pop" sound from the dash, and it suddenly blows warm again, for a short while, and only while im stationary. it slowly gets colder again when i start moving (engine is still hot according to the gauge)..

AC works "ok" (i say ok, because that too acts a bit funky from time to time, like it blows cold right after starting, and the hotter the outside is, the warmer it blows)..

sooo... winter is coming yet again to norway. and i don't want to spend the winter driving around in a cold car. i can deal with the funky ac in the summer, but driving in -10c is a bit worse.

the dampermotors all seem to work, i get full flow through them to start with, then one or more gradualy starts closing. i can hear the fan working hard against a door inside the dash.

they doo as i say seem to work because i cannot recreate the problem in the garage while looking at the motors, it only happens after a while when driving..

any experts that has any advice? all advice is good advice for me right now. i'm a vw guy who happend to get this V70 dirt-cheap from my uncle as he had two cars after a divorce.

and sorry for the wierd sentence buildup and back and forth on the issue. not too god on the english language

Post by **abscate** » 12 Sep 2017, 11:47

The Volvo climate control is full flow heater core, air mix to make up temperature requested by the ECC control unit.

My guess is the mix door is broken inside - no codes for the ECC as all the motors move as requested, they just don't connect to anything!!

dsno · Post by **dsno** » 12 Sep 2017, 12:47

but it does work, from time to time..

how much of a PITA is it to get to the doors? full surgery trough through the tailpipe?

Post by **abscate** » 12 Sep 2017, 13:06

Its about 10 hours labor to remove the dash and climate system to repair. It is stupid labor though, not labor you want to pay $100 an hour for

Post by **850 LPT** » 12 Sep 2017, 13:14

dsno wrote: ↑12 Sep 2017, 11:17 and sorry for the wierd sentence buildup and back and forth on the issue. not too god on the english language

You are doing just fine my friend, pretty impressive actually!

dsno · Post by **dsno** » 12 Sep 2017, 13:21

abscate wrote: ↑12 Sep 2017, 13:06 Its about 10 hours labor to remove the dash and climate system to repair. It is stupid labor though, not labor you want to pay $100 an hour for

i'm quite fine doing this myself

and laborcharges for a mechanic in norway (atleast dealership labor) would run me about $150 pr hour. so i can use a good weekend on this myself if i have too.

does it exist a book, pdf or anything on the matter?, the furthest down the dash i've been is taking the top of in an attempt of getting rid of that god damn squeeking noise that the dash makes

dsno · Post by **dsno** » 12 Sep 2017, 13:23

850 LPT wrote: ↑12 Sep 2017, 13:14
dsno wrote: ↑12 Sep 2017, 11:17 and sorry for the wierd sentence buildup and back and forth on the issue. not too god on the english language
You are doing just fine my friend, pretty impressive actually!

thanks

Post by **scot850** » 12 Sep 2017, 15:24

Welcome dsno. Look for the replacement instructions in the database for the evaporator. It will possibly be for an 850, but the V/S 70 are almost the same. The main differences are the airbag in the steering wheel (yes it has to come off) and the top section of the dash is slightly different. You have to remove several hidden screws by first removing the air vents and also the 2 on the ends of the dash need the short tubes to be prized out and there is a screw behind there. There is also a screw under the small speakers on the dashboard top.

Next you need to remove the glove box liner and undo the 3 10mm bolts that hold the passenger airbag in place. The last 2 screws are hidden in front of the speedometer unit in front of the clear plastic cover. All screws are the same T25 Torx.

I wouldn't rush to remove the dash just yet. Have a good look at the cabin temperature sensor hidden behind the small grill to the left of the ECC unit. To access the sensor, you have to remove the radio, and ECC units and then feel in behind the dash. There is a connector on the back of the unit (green usually) that unplugs and then the tricky bit. There are 2 tabs that have to be compressed into the sensor body and they are hard to feel as you can't see them easily. If you are looking from the front seat, the tabs are at a 4 and 10 o'clock position if I recall. Once you remove it, be careful as there is a rubber seal that attaches to the front of the sensor and it tends to stick to the dash and then fall down behind it!

Clean all the crap that in inside the unit and make sure the little suction fan is free to turn. I usually use a small artist paint brush and cotton buds with some rubbing alcohol (IPA). Once clean, a small amount of silicon oil on the fan spindle and then I blow the fan with an air line to spin it up in case it is tight and it also removes excess oil.

I think you may find that is the issue. If the unit cannot draw air past the sensor in the middle of the unit it assumes the temperature and not what it actually is.

I'd try that first before ripping the dash apart.

Here in this thread I show a couple of pictures what the part looks like:

viewtopic.php?f=1&t=70611&hilit=cabin+t ... ure+sensor

Neil.

dsno · Post by **dsno** » 13 Sep 2017, 12:11

thanks for the reply. the sensor is free of any dust and crap that might get down there. and the fan moves freely. and it didn't help. did that about 1 year ago now.

looks to me that i just have to set a side a weekend to start digging into the dashboard :/
oh well. just another thing to add to the list. i've got a complete timingbelt job on my list too

is there any way of checking the sensor? in my world (vw golf mk2 world). we've got the infamous "blue" tempsensor. its possible to readout the resistance at a given tempereture to check if its within the threshold.

don't know what kind of sensor the cabin air temp sensor is (thermistor?). if so it should be doable. if it exist a chart of known good values

Post by **scot850** » 13 Sep 2017, 15:31

Which sensor are you talking about when you say down there? There is a sensor beside the fan/resistor pack monitoring incoming air I believe, and then there is the one in behind the dash up to the left of the ECC control unit as shown in my link. If that one is 'working' they do go bad and can info can be scanned by Volvo/Vida. I had that issue with a 98 V70XC and replacing it fixed the issue. As to the specs., not sure I have ever seen anything on that part.

Neil.