Heater/AC not working

[Casper23]

I am currently having a problerm with my Toyota IQ2 2009. The heater control assembly unit (55900-74010) has a blank screen and none of the functions for heater, A/C work with the exception of the hazard lights. We have bought a replacement unit which hasn't solved the problem, taken the car to 2 garages (one being toyota) and they have checked the fuses, relays and were unable to locate the issue. The LED display screen lights up when turning on the engine however it is blank. 

Any ideas where the problem may be coming from? In this weather I am unable to clear the windscreen so I am eager to get this problem sorted. Any help would be much appreciated!

[Given]

Long shot getting a reply given the original post date, but I have the same problem.  Toyota state the fault is the heater control unit, with a new unit costing £960.  However, the same unit on eBay is £65.  

Did you find the cause and resolve the problem?

[craggle]

There is an associated heater / AC ECU located underneath the heater unit behind the dash. It can be located in 10 minutes but involves removing the centre console and gear lever surrounds. 
Maybe that has failed in some way.
 

Craig.

[Given]

Cheers.

The fault was not with the heater control unit.  After many hours of investigating a local garage found it was related to a faulty aircon pump.  Each time the car was started the system tried to reboot, but failed, hence the display appearing briefly. 

FYI, the £65 unit on eBay was from the Aston Martin model, was compatible just not the part that needed replacing.

[sebwout]

Hi

I have the same issue as you after running for 4-5 minutes the screen goes blank.

I've changed the ECU but no effect

What was the issue with the compressor? Is there any cheap solution (like the magnet trick for the flow sensor)?