AC blows hot air, instead of cooling my Innova's cabin: Finding a fix!

I think significant time and quite some money has been spent on this issue - however, the issue still persists.

BHPian Alphard recently shared this with other enthusiasts.

Hi Team,

I am writing to you to seek help with a problem that I am facing with my 2010 Toyota Innova 2.5V D-4D.

Problem Statement

My Car has an automatic AC and the AC normally works well and cools the entire car cabin effectively. However, sometimes, the AC starts heating the cabin instead of cooling the ambient air - this issue happens intermittently.

Problem Description

If I switch on the AC, sometimes it will start cooling normally and sometimes it will start heating the cabin.

When the AC starts cooling, the AC will keep cooling regardless of how many km or Hours the vehicle is driven. However, if the vehicle is stopped and then restarted, there is no guarantee that the AC will resume cooling or start heating the cabin instead.

If the AC starts heating the cabin, the AC will keep heating the cabin regardless of what temperature is set on the AC control panel. Once the AC starts heating, it works completely opposite of what it is supposed to do i.e. if I lower the temperature on the AC control panel, it will start blowing more hot air in the cabin.

When I started the vehicle, the problem with the AC was indicated by the AC control panel going dead and the blinking of the AC defogger light (i.e. the small amber-coloured LED on the defogger button on the AC control panel) for about 20 -25 seconds. Once the AC defogger lamp stops blinking, the AC control panel starts - however the AC may or may not cool the cabin. Moreover, this problem seems to affect only the front AC air vents on the dashboard - the rear AC vents keep cooling the cabin.

I have checked online and even visited Toyota Service Centre 4 times in the past 2 -3 months to get this issue addressed. Initially, they had re-programmed the AC control panel and told me that the problem had been resolved. However, despite the AC control panel re-programming, the problem had re-occurred and I have been visiting them repeatedly to get the issue resolved.

In one of my recent visits to the service centre (Aug 1st week), my vehicle was kept with the Toyota Service Centre for 3 days to enable them to properly diagnose and fix the issue. They had replaced the AC control panel giving me assurance that the problem had been solved. However, despite their best efforts, the problem occurred with the vehicle being driven for less than 100 km since taking delivery of the vehicle.

After the problem reoccurred, a team from Toyota Service Centre was sent to my home to check the issue. During their visit to my home, we took the vehicle for a trial run and a different issue with the AC control panel cropped up - the AC panel would keep turning on /off, display random numbers and become unresponsive during the drive. The Team took the vehicle with them so as to attend to the issue. They investigated the issue and I was informed that it was due to some loose electrical connection. The vehicle was with the Toyota Service Centre for 4 days and now the original AC problem has reoccurred with the vehicle being driven for less than 100 km.

I think significant time (i.e. total of 8 days on 4 occasions) and quite some money (~= INR 12000) has been spent on this issue - however, the issue still persists.

The staff at Toyota Service Centre has been helpful, sensitive and responsive to my concerns however now I am at my wit's end trying to understand how to get the problem fixed.

I raised a Grievance with Toyota India last week however they have just routed me back to the same Toyota Service Centre. Given the past experience, I am not sure whether taking up this issue with the same Toyota Service centre will do any good.

I would like our members to guide me based on their rich experience and technical knowledge and advise me on the way forward.

Thanks & Regards

Here's what BHPian Jeroen had to say on the matter:

If the Toyota mechanics start swapping electronic parts or reprogramming stuff I would hope they did a thorough analysis. This means hooking the car up to a proper OBD analyser that can access the AC system. Ask them for the error codes. If they don’t know or say it can’t be tested, you know they are lying.

Reprogramming the computer is unlikely to have been the problem in the first place.

I believe this problem to be more likely related to one of the sensors, flaps and or valves that control the airflow. Not sure how they operate on this Toyota, pneumatic (vacuum) or electrically.

Whereas electronic problems can usually be diagnosed easily, if you have access to a good OBD analyser, everything else is a lot more complicated. It also means in most cases taking the whole dashboard apart! Ask me how I know!

So you really need to find a very competent mechanic and it might take quite a few hours to find the problem.

Good luck

Here's what BHPian shikh_oberoi had to say on the matter:

Please check if the outside temperature sensor is working correctly. How much temperature does the car show on the screen?

AC mechanic damaged my Verna's outside temperature sensor and the car was blowing hot air. The AC panel showed a temperature of 8*C. He fixed it and the temperature changed to 38*C and it started cooling again.

Here's what BHPian NomadSK had to say on the matter:

Hey, seems I had almost a similar problem in my vehicle, check post#84

The local FnG guy went below the dashboard on the passenger's footwell and corrected the blender door actuator's position which was stuck in its position. That’s what he told me, I couldn’t get the exact troubleshooting scenario because of the language barrier and while he was fixing it (I thought it would take some considerable time) I went to get some water and while I came back he said, it was fixed. At that point, I was a bit sceptical. One tends to trust more service centres than a local mechanic.

Afterwards, I tested it with a few scenarios (auto/manual, heating/cooling), it’s been a few months now and it’s working fine. I couldn’t update the thread, since I didn’t exactly know what he did in those few minutes. He even didn’t charge me for this, since he had earlier taken the payment for OBD scanning.

So I guess it’s all about correct troubleshooting with an OBD scanner and the correct fault finding. Don’t let anyone implement the hit-and-trial method. At the Toyota service centre, they told me, that they would have to pull down the whole dashboard only for the diagnosis.

Here's what BHPian dhanushs had to say on the matter:

The heat in the hot air is from the engine coolant and there is a valve that controls it.

Most likely in your case that valve is a problem and it brings in hot coolant even when not asked for. You have to go to a dedicated Car AC Mechanic to solve the issue.

I had a similar problem in my Ford iKon years back and the jugaad done was to bypass the coolant completely. i.e. I only get cold air.

Check out BHPian comments for more insights and information.