IQ3 HVAC Heater/AC Issue

[sebwout]

Hi All!

I have a desperate problem with my iQ 3 (automatic A/C).

It all started a day after letting my iQ sitting for a few days I went to start it and to my surprise it crank and did not start! First time I ever see this with an iQ...
Tried again, no start...
3rd time it starts!
Weird...
Then on the way after 4-5 min the whole AC control panel starts flickering and then stops working.

The panel goes blank and none of the buttons function except the Hazard light switch.

The heater fan also stops working.
The next day I try again, the car starts right away and the AC unit works again but only for 4-5min and then starts again to flicker and then stops working totaly.

I first thought it was the AC ECU/Amplifier that sits under the AC unit center console. Mine is 88650-74032. Impossible to find the same unit second hand.
Luckily, I see in Toyota's docs that unit nr 88650-74031 is the same but they changed to 74032 in 2011. My business partner also has an iQ3 so I try with his ECU (which is 74031 and not 74032 but also had automatic AC so it should work!) and the problem remains the same.

I try his control panel, same problem.

I check all fuses are OK

When the problem happens, I can feel the AC ECU is quite hot to touch in some places. The situation is the same with both ECU tested.
When I connect my OBD reader I get error code E0164 : lost communication with HVAC Contro module.
When I check in the OBD reader for live informations over AC unit I see infos are flickering like if the AC unit was starting over and over again

My Battery is OK, starting is strong. 13.9V with all lights up. Tried with a big jumper Battery nothing changes.

My AC system is empty - I never use AC. And I have the flow sensor error code from the beggining but have never try to repair it as I don't use AC.

Any idea what could be my problem?

Thank you so much in advance for your help!!
 

[flash22]

go and get your Battery and alternator tested - auto or manual gearbox?

I would disconnect the heater fan or remove the fuse (HTR B 40a) and see if it comes back to life, also check/clean/replace the cabin air filter

cabin filter location

 

[sebwout]

Hi 

Battery is tested and good. Charging at 13.9v even with lights on.
fuse is OK
As for the filter I really doubt it has anything to do with electronic stuff but I'll have a look
Thanks for your answer

[flash22]

airflow can affect how the system operates a stuck/jammed fan will cause issues with the a/c amplifier , a badly clogged filter, is like trying to breathe through a straw

with auto climate the system will try to start the pump if the pump/valve is bad it can overload the AC amp

unplug the electrical connector on the compressor and also disconnect the pressure switch, running it with no gas/oil has likely killed the pump

[sebwout]

Thanks for your reply. I see what you mean. That would explain why some parts of the Amp circuit would be hot to the touch.
I am getting the circuit filled up today and have magnets coming from Amazon to try the magnet fix of the flow sensor.

[sebwout]

AC filled up, filter changed, Battery post cleaned, problem is still there.
I am getting the subframe down tonight to have access to compressor to put the magnet and check all connections.

[sebwout]

Update:
I tried the magnet fix but it did not work
While I was at it I tried disconnecting the big electrical plug coming out of the compressor.
No more issue with compressor unplugged. Heating works as it should

So I guess I am good for a new compressor

[flash22]

glad you got to the bottom of it