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Old 13th May 2011, 09:34   #16
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

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I own a Baleno!
Mr. VinoTH, you know whom to call. Do it fast as mercury is touching 42 C.
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Old 18th May 2011, 12:13   #17
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

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Originally Posted by Jaggu View Post
Electric fan might not even kick in at 80 kph. So i dont think that is a problem. One thought, is there any wire in front which is getting shorted at high speeds due to wind speed

As i mentioned early its a funny situation.
Had the wirings checked; no short-circuits at any place. its is indeed funny

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Originally Posted by SS-Traveller View Post
I think Tanveer said it...

Check if both the main and condenser fans start up as soon as the AC is switched on. If either fan fails, the AC will still work, but there won't be enough cooling of the condenser (esp. when the car's radiator needs to get rid of a lot of heat from the engine when driving at high speeds) - and a little switch will then cut the AC compressor out and stop cooling.

Also check for a AC compressor clutch slippage / failure.
The fans are working alright. Will check on the AC Compressor clutch. A visit to Cool Days is pending

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Originally Posted by tsk1979 View Post
If your condersor fan is not rotating, your AC will cut off due to condensor overheating. Many modern AC systems have this feature.

So if you have dust and debris in air flow path, you will see frequent AC cutoff.

Now imaging a condensor fan, which has a mechanical fault. When car is not moving fast, the fan is blowing air towards the condensor, and as per newtons law of motion, the fan is getting pushed outwards.

At high speed, lets say 80-90kmph, the air flow hitting the fan will be significant, so the fan is going to get pushed inward.

Imagine a mechanical defect, where if the fan is pushed, it moves on the spindle slightly, leading to spindle rotating, and fan not rotating with the spindle. This will be a rare case.

Imaging a defect inside the fan motor, so that when fan is pushed due to airflow, the spindle jams.

If there is a sensor inside the AC mechanism which is designed to turn off AC when fan is not rotating, AC will immediately cut off.
However, if such a mechanism is not there, AC will cut off when condensor temperature reaches above a certain level, which will happen very quickly if fan is not rotating.

I have had such an issue. The condensor fan was not rotating , therefore the AC was cutting off regularly. After the condensor fan was replaced things were fine.

In the above case, lets say fan is lose on spindle.
Airflow pushed it towards the condensor, and the blades touch the shroud, and at high speed spindle rotates, but fan is stationary, actually blocking the airflow. This will lead to temperature increase immediately within a few seconds. So after 15-20 seconds the safety circuit will cut off the condensor. In such a case Ac will come on intermittently.

Since OP has not mentioned that AC is going on/of/on etc., I suspect that when airflow speed is high, the spindle itself is getting jammed, causing a speed sensor to cut off the AC.

A rared case would be a problem with some ECU sensor, which is giving some wrong signals leading to AC cutting off.

For example, if some sensor detects engine overheat, it will first cut off AC to slow down overheating.

Usually this leads to a error code in ECU. Since there is no error code in ECU, it looks like some secondary sensor in ECU.
Checked the fans. No mechanical issues. Had replaced the fans for trial with working fans of another car; the issue still persists.

Also, the ECU does not give out any error code when the AC cuts off above 80kmph

It is indeed a very weird situation, especially in this heat
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Old 18th May 2011, 13:43   #18
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

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Originally Posted by rideon View Post
...
It is indeed a very weird situation, especially in this heat
Check if AC recirculation mode is working, and that no outside air coming into the cabin.

I'm not so sure about the working of a AC divertor valve in a Honda city, but you might also want to check it out, as that too affects cooling.
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Old 18th May 2011, 21:20   #19
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

Yup sometimes its as simple as that ^^ But seems to be this is a case of a problematic compressor unit.
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Old 11th May 2012, 18:44   #20
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

@rideon - sorry to restart an old thread, but I'm having a similar issue with my i20. I'm getting AC cut off in the fourth gear (works perfectly as long as I'm on 3'rd gear). not sure what the reason is.
did you find out and fix the root cause ?

P.S. This is a second hand car I bought a while back in the winter time.
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Old 12th April 2014, 09:27   #21
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

Restarting this old thread, I am also facing this problem in my logan. At stand still AC works very fine, but if I take the car above 80km per hour the AC does not cool. Can anybody have a valid reasons for this kind of behaviour.

Visited AC mechanic , he said to do AC servicing, I have top up gas, but to no effect.
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Old 12th April 2014, 12:03   #22
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Default Re: AC Cut-off above 80kmph - City ZX Vtec

It could a variety of things - First there is a cut off if the load of the car is > 85% it is to do with throttle sensor and some other settings. This is the hard fix. the easier ones have to do with condensor fan not working and low AC gas. Can you try if the AC works on 2/3 gear at 80 kmph compared to 5th gear at 80kmph. Could be that the Compressor lost compression and cannot work at lower engine rpm?
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