A.C. Malfunction when on Auto

[Ivo]

Hi fellas, my AC is doing something strange when on Auto control. Normally I set the desired temp and let the system take care of the rest. At the last service they did not have the filter element in stock so the left it out and week later when I had time I dropped back in and they installed it. All was good! About a week after that It was a warm day (32c) got in the van and there was a strange noise coming from below the dash on passenger side., sounded like the fan. Then I could smell an electrical burning smell..... it only lasted for a few seconds but was there.

Since then the AC system has been playing up when in Auto mode. It will start and run for a few minutes then the fan drops to nothing even though the display shows it on full speed. I switch it off for a few minutes and sometimes it works normally and other times it does not. Now here is the strangest part, if I just run it in full manual mode it works perfectly! If I switch it over to auto it some times works or it shuts down.

I dropped into my mechanic , explained what was happening so he connected it up the VW diagnostic computer and scanned it. Sure enough there was an error code! It basically says climate control. He reset the fault and lets the computer run another full test and its all clear. He then does the same again with the engine running and the AC on.... works perfectly again in auto mode.

I set of again and all was good. Stopped at the hardware store, came out 1 hour later and it would not work. Shut it of, let it sit for a few minute as I drove with the windows down. Then started in manual mode...and it worked again. Only other thing is it seems to happen on warm/hot days.....when you need AC the most.

So..... has anyone else had something like this happen? Any suggestions on what to look for or check? I get the feeling its a sensor the controls the Auto mode and thats why the AC still works in manual.

2005 T5 Multivan.

[gregozedobe]

From the symptoms you have described I would be much more suspicious of the mechanism that adjusts the fan speed when in auto mode - presumably it is some kind of small motor/solenoid that alters which resistor the power for the fan goes through. It sounds like the fan speed control itself is fine (works OK in manual mode).

Caveat - my T5 has manual HVAC, so I have no direct experience of the automatic T5 ones. I can't remember reading of this particular problem before, so it seems it is uncommon.

[Deeceer]

32 degrees C is warm?

Sorry, couldn't resist

[Ivo]

32 degrees C is warm?

Sorry, couldn't resist

Yeah yeah everything in Queensland is bigger and better LOL ! It was 42 here on Sunday....I think thats hot but where does that fit into the QLD'er scale? You blokes probably have your cardigans on the heater on full eh LOL!

Turns out the fan/blower unit is buggered.....only $620 for the part plus fitting! Hopefully it turns up Wednesday?

[Tornado T5]

Yeah yeah everything in Queensland is bigger and better LOL ! It was 42 here on Sunday....I think thats hot but where does that fit into the QLD'er scale? You blokes probably have your cardigans on the heater on full eh LOL!

Turns out the fan/blower unit is buggered.....only $620 for the part plus fitting! Hopefully it turns up Wednesday?

The extended factory warranty offer I saw on the counter of the service dept. looks more attractive now that i think about it....3yr/60,000km approx. $1,900

[Ivo]

More good news None in stock Australia wide....has to come from Germany....maybe 2 weeks!

[gregozedobe]

Turns out the fan/blower unit is buggered.....only $620 for the part plus fitting! Hopefully it turns up Wednesday?

If you are paying for that out of your own pocket (ie not a warranty job) I suggest you keep the old one and see if it can be fixed cheaply - that way you can either keep it as a spare or flog it off to save some other poor sod some $$$ and also recoup some of your costs.

Often there is only one small component that has failed, but these days the manufacturer only supplies a complete unit (and strangely enough, the complete unit always seems to cost WAY more than the component).

As an eg some Golfs (and similar VAG vehicles) have an ABS unit that frequently fails. VAG charge approx $3,000 for a new unit, but there is a mob in the UK that replaces the duff sensor that is usually the actual fault, reconditions the whole thing and sells the refurbed unit for under $200 (IIRC).

[Ivo]

The mechanic has pulled it apart and it needs new brushes. None in stock down here but they have ordered in from Brisbane and should be here Friday!

[Ivo]

It gets better........


The mechanic has repaired the electric fan, tested it on the bench then fitted back in place. It works perfectly and you can here it change speeds as we adjust it on the dash. Only problem is......there is barely any air coming out the vents. Auto or manual mode, it makes no difference, redirect for windscreen defrost...nothing either!

I delayed my departure for my weekend trip away so we could get the repaired fan unit fitted and have AC for our trip. The rear AC is working perfectly, cooling and blowing as it should but there is something strange going on with the dash unit. The air is trapped inside somewhere?? After 4 hours in the car we made it to our destination. A few short trips over the weekend and still the same.

On the trip home I was sitting on 120km/h and hit a nice bump in the road.....I heard a small thump under the dash, it sounded like a vent or flap changing position and there was more air coming out the front vents. Not the full amount but more than before.


My mechanic has a VAG 5051 computer and a Bosch diagnosis system as well. He ran both systems on the car and found no faults or errors in the climate control system. So we can't help but think there is a vent that is broken or jammed somewhere. I will take it back later this week for him to have another look.

Usually there is water that drips out from under the car but there has not been any for a while now. Could this have something to do with it? Any other ideas what it could be?

[Tornado T5]

Prior to this weekend we had very humid days in Melb so I noticed far more water under the T5 then normal, in fact high 30's and high humidity matching a FNQ day. Your smaller amount of water dripping could be based on the fact the faulty unit is not working fully and thus not removing as much moisture from the interior air. Hope you get some success! I take it when you switch the air output selector from feet to face to windscreen it shut's off fully from the prior setting or does some air remain flowing. I'm not sure but does the control for this work on vacuum pressure or is it an electricallly controlled unit?