2002 v70 AC/Heater switch not functioning

auburneduprof · Post by **auburneduprof** » 25 May 2014, 17:50

Two weeks ago an alternator went and I had it replaced. Yesterday, the switch for the AC stopped doing anything. AC still blew- I"m assuming maybe the automatic system, but the fan switch doesn't work. I tried resetting the ECU, but no joy. My next thing to try, based on forum searches, seems to be the relay for the environmental system, but I have no idea if that makes sense. Please help! Thanks in advance.

Post by **oragex** » 26 May 2014, 05:38

How did you reset the ecu? I take both battery terminals off for about 15h. Remember when plugging the battery back to have the ignition key in position II (if you didn't when replacing the old battery, is probably the reason why the a/c switch is not working). To check the ecu has been reset, the center panel switches come to a default setting.

auburneduprof · Post by **auburneduprof** » 26 May 2014, 07:26

I turned fan and radio off. Waited 10 min. Took positive then negative terminal off. Touched them together for 10 secs. Put key in position 2. Connected first positive then negative. Would that not work?

Post by **abscate** » 26 May 2014, 08:02

Yesterday, the switch for the AC stopped doing anything. AC still blew-

We need to understand the symptoms better, I think.

Start car.
Put AC into auto. Select temperature well below ambient to engage AC.
What happens? Is the AC light on/off and/or is the fan blowing?
Do you get cold air?
Do you hear the compressor engaging with climate on auto and temp set well below ambient?

Acronym dictionary

ECU is engine control unit...this is a long way away from our problem.

ECC is the electronic climate control....the whole System. People often use this to mean the control unit for ECC, which is the box in the dash on P80 (2001 and earlier cars) which can get confusing. I'm not sure where the ECC control unit is on P2 cars but experts will chime in here.

Troubleshooting climate controls is most successful looking for component and wiring failures first, before jumping to control units which rarely fail.

Fellow sailor here...WWP crew on San Francisco Bay whenever I can....

auburneduprof · Post by **auburneduprof** » 26 May 2014, 08:10

Fair enough: I have the base model so there is no temperature setting. I turn the key on, and there is no fan, and the switch makes no difference- after driving down the road, a fan comes on and blows cold air, but it is also not controllable by the switch. After I turn the key off, the fan (and yes, it's the interior fan, not the engine fan, which also runs for awhile) still blows. That's all the data I have. Thanks so much for helping, and I envy your Eurovan camper.

Post by **abscate** » 26 May 2014, 08:18

Sorry my post sounded preachy. Trying to help.

It sounds like you have MCC or manual climate control and the fan is not responding to the fan switch?

That should be simpler to diagnose at least. I don't like that it stays on for a while. The ECC units do that to dry the evaporator and stop it from corroding. I don't think the MCC units do.

We need a kind soul to post a link to the wiring diagram for your car. Volvo asks the site moderators to not do this, but users can.

I'll send 12 knots of beam reach breeze to AL while we wait.....

Post by **precopster** » 26 May 2014, 08:30

There's a temp sensor probe in the climate unit that can break causing the unit to suddenly stop. It's located just behind a small grille in the top right hand corner of the climate unit

To remove the climate unit disconnect the battery (to avoid an SRS module problem) then pry the small trim between the gearlever and the climate fascia panel off. Then the torx screws are visible.

Once you draw it out the connectors come off and you can begin to disassemble the unit. The temp probe is accessible once the fascia plate is removed. You can solder it back into a loop.

auburneduprof · Post by **auburneduprof** » 26 May 2014, 11:14

Went to drive to store- car sitting in shade. Switch works, fan works, blows cold. Car sits in 90 Alabama heat while at store- I turn the car on and back to the switch not working.

So, the fan is good, the switch is good, and the AC is good. What next?

Post by **abscate** » 26 May 2014, 15:26

Sounds like a relay problem of some sort.

Another possibility is the ignition switch electrical part is going bad.

auburneduprof · Post by **auburneduprof** » 26 May 2014, 18:25

Definitely heat related. Now that's it's cool again, no problem. Hmm....