A.C. Malfunction when on Auto

[Silver Caravelle]

Hi IVO,

Dis you get this sorted in the end?

Cheers,

Scott

[Ivo]

The saga continues! The motor has been rebuilt and runs perfectly but the air is still trapped in the dash The rear AC is working perfectly and if I set the front temp on about 19 it blows just a little air. If I set it any colder it trips out the entire system after about 30minutes. Then I have to turn it off and let it rest for 10 minute then start the AC again. All the actuators in the dash test as ok on both VAGCOM and the Bosch System...so the motor is working but a flap is not.

We pulled the pollen filter out and you can feel the air speed change with higher and lower settings. Its blocked somewhere after the "small radiator" in there. That means most the dash has to come out to get at them Its just been a matter of time to schedule it for a few days to get it all apart. Its booked in next Wednesday for a few days.

[Silver Caravelle]

The saga continues! The motor has been rebuilt and runs perfectly but the air is still trapped in the dash The rear AC is working perfectly and if I set the front temp on about 19 it blows just a little air. If I set it any colder it trips out the entire system after about 30minutes. Then I have to turn it off and let it rest for 10 minute then start the AC again. All the actuators in the dash test as ok on both VAGCOM and the Bosch System...so the motor is working but a flap is not.

We pulled the pollen filter out and you can feel the air speed change with higher and lower settings. Its blocked somewhere after the "small radiator" in there. That means most the dash has to come out to get at them Its just been a matter of time to schedule it for a few days to get it all apart. Its booked in next Wednesday for a few days.

IVO,

This is worth a try before you go to the pain of pulling the whole dash apart.

If you can some how access the vacuum actuator for the recirculation flap (somewhere under the left hand side of the dash), this may be where the air leak/perforation is. At least this was the case on my previous T4. The T5 might be laid out slightly different. The symptoms you describe relating to the temp settings may mean the recirculation flap is not closing when A/c is set below 19 to 20 c......because of an air leak relating to the recirculation flap actuator ......which gives the impression that it is a temp related….. but really means an vacuum leak because the flap closes below this temp range.

Clear as mud!

Cheers,

Scott

[Ivo]

Its not vacuum actuated, they are electrically operated.

[Ivo]

Dash is out and still no luck We have stuck a camera down the ducts to check for blockages....nothing! Still got some more investigating to do though.

[Ivo]

A few pics of the chaos!

[gregozedobe]

Are we having fun yet ?

I hope you find it after all that work.

[Ivo]

Oh yeah heaps of fun and to top it off, our second car (79 280e merc) has decided to play up as well.

[BrianJ]

Wow, I hope mine never does this!!

Have you considered the recirculate vane, it might have slipped and blocked off the source air so the fan would be trying to pull a vacuum, and therefore have no output.

Brian

[Tornado T5]

I really hope you solve it although I'd go banana's if it were fixed and everything was put back together and there was one screw left over and a small rattle. Good luck.

[Ivo]

Well.....its back together....but not fixed lol!

We have narrowed it down two possible causes. The rebuilt fan is not working hard enough....although it really is pumping out a lot of air into the pollen filter. Maybe its just not enough. We are hoping to find a T5 owner who will let us test his fan and see if the output is stronger.

The second possibility is that the evaporator is somehow blocked. The passage ways are restricting the air flow through it. We have stuck a camera down from the top vents to the evaporator and there is nothing blocking the ducting and with the pollen filter out we can see the other side of the evaporator and there is nothing blocking it. So maybe the evaporator has been damaged somehow??? The mechanic made a tool up to poke through the evaporator to enlarge the holes for the air to flow through. He did this about 20 times and now there is more air coming trough. But that could just mean the weak fan is able to now push more air through or the evaporator is buggered!

Now the old Merc is in the workshop to be checked for its problems and sometime in the new year we can get to the bottom of the AC/fan problem.

[BrianJ]

A few more observations

I noticed with my dash fan that if the right outlet control knob was set clockwise from the dash air to the feet position by just 1 - 2 minor graduations that the dash air is almost reduced to nothing. This made me think about what you said about the amount of restriction through the cooler unit, and what I realised is that if there is any way for the fan pressure to be relieved via another leakage path then almost nothing comes out of the dash vents.

I recall reading somewhere a thread which talked about how the right outlet control knob had no stop and some people always wound them in the same direction until the cables wound up and seized, which would cause the control to become misaligned with the indication on the dash. Meaning that it could be directed slightly to the feet or demisters when pointing to the dash outlet. If this happened then there would be next to no air from the dash vents.

Food for thought.

Brian

[Silver Caravelle]

Well.....its back together....but not fixed lol!

We have narrowed it down two possible causes. The rebuilt fan is not working hard enough....although it really is pumping out a lot of air into the pollen filter. Maybe its just not enough. We are hoping to find a T5 owner who will let us test his fan and see if the output is stronger.

The second possibility is that the evaporator is somehow blocked. The passage ways are restricting the air flow through it. We have stuck a camera down from the top vents to the evaporator and there is nothing blocking the ducting and with the pollen filter out we can see the other side of the evaporator and there is nothing blocking it. So maybe the evaporator has been damaged somehow??? The mechanic made a tool up to poke through the evaporator to enlarge the holes for the air to flow through. He did this about 20 times and now there is more air coming trough. But that could just mean the weak fan is able to now push more air through or the evaporator is buggered!

Now the old Merc is in the workshop to be checked for its problems and sometime in the new year we can get to the bottom of the AC/fan problem.

Hi IVO,

Is there any leak in the ducting to the vents or could the ducting have popped off at the vent end causing reduced flow when being put back together?

It is unlikely that rebuilt fan is not working hard enough, they either work or they don't in the end. Probably only needed some new brushes I assume?

All the best.

Regards,

Scott

[Ivo]

FIXED!


Almost 3 months with basically no AC over summer. I'm almost embarrassed to say what it was.LOL!

If you recall, the blower motor shorted out, a new one from VW was $620 with a 2-3 week wait from Germany. So my mechanic sourced some new brushes and repaired the electric motor. Motor was installed and very little air was coming out the vents.

Motor could be heard changing speeds, with pollen filter removed we could slide our hand up in the slot and feel the air movement. Dash out, cameras down the ducting, nothing blocking it. All flaps operating correctly. Suspected it was either the fan had not enough force or the evaporator was blocked.

My neighbour is an auto electrician/AC mechanic and he offered to have a look. We decided that the dash had to come out again so we could get at the entire system again. 2 hours later we had the dash out and started testing. Everything worked as normal but still no air.

After some head scratching he decided to pull the blower out again. Plugged it into the controls and fired it up......."hmmm does that look right, I think it should be turning the other way". Got his battery pack and reversed the power supply....hmmm it spins that way as well???? Still feels like the same amount of air being thrown off??? So installed blower back into housing but used battery pack to power it up in reverse.......

SUCCESS!!!! Air is blasting out all the vents! Turns out when the mechanic had rebrushed it he put the wires in backwards. When it ran in reverse it still created that much turbulence in the housing it was forcing some air through the system!

Now its fixed and I have my AC back! WoooHoo!

[Silver Caravelle]

FIXED!


Almost 3 months with basically no AC over summer. I'm almost embarrassed to say what it was.LOL!

If you recall, the blower motor shorted out, a new one from VW was $620 with a 2-3 week wait from Germany. So my mechanic sourced some new brushes and repaired the electric motor. Motor was installed and very little air was coming out the vents.

Motor could be heard changing speeds, with pollen filter removed we could slide our hand up in the slot and feel the air movement. Dash out, cameras down the ducting, nothing blocking it. All flaps operating correctly. Suspected it was either the fan had not enough force or the evaporator was blocked.

My neighbour is an auto electrician/AC mechanic and he offered to have a look. We decided that the dash had to come out again so we could get at the entire system again. 2 hours later we had the dash out and started testing. Everything worked as normal but still no air.

After some head scratching he decided to pull the blower out again. Plugged it into the controls and fired it up......."hmmm does that look right, I think it should be turning the other way". Got his battery pack and reversed the power supply....hmmm it spins that way as well???? Still feels like the same amount of air being thrown off??? So installed blower back into housing but used battery pack to power it up in reverse.......

SUCCESS!!!! Air is blasting out all the vents! Turns out when the mechanic had rebrushed it he put the wires in backwards. When it ran in reverse it still created that much turbulence in the housing it was forcing some air through the system!

Now its fixed and I have my AC back! WoooHoo!

That's great news in a round about prolonged sort of way.

I think I would be sticking with your neighbour for future work rather than the other mechanic!

Cheers,

Scott