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Old 10th June 2022, 10:04   #1
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Honda City AC short-cycling | Compressor turning on and off within seconds

Hi all,

I have a Honda City ZX 2006 which has done 1,03,xxx KM.
Its been running flawlessly for the last 15 years and regular engine oil and filter changes are done.
Nothing much has gone wrong with it and its been reliable and refined all through.
A few days ago I observed that the AC compressor started and then stopped within maybe 5 seconds and then started within 5 seconds and so on. The air from the vents was only slightly cool and was basically useless in this summer heat. I checked by hand and found the suction pipe got cool and the condenser pipe got hot when the AC keeps cycling like this. I searched on the internet and found low AC refrigerant to be a common cause for this.


I showed it to a local car AC shop (works only on car AC).

The guy opened the bonnet and checked the behaviour of the compressor and said its probably less gas. He connected a gauge to the low pressure valve and got a reading around 50psi when the compressor had been off and it went to around 30psi once the AC was switched on and started short cycling. He said the refrigerant is not low. He said maybe the engine is overheating causing the compressor to switch off, so he openend the radiator cap to check the coolant and found it was full and looked good. No 'Engine overheated' light or 'Check Engine Light' on the Instrument Panel. He felt the pipes and said that the AC system seems to be fine and it must be some electrical fault. He asked if I had got any accessory installed like lights, horn etc. I replied that only music system was installed around 15 years ago and no other accessory was ever installed. He asked me to remove the battery for the night and check the next day.
I did that and found that the same issue persists. I am yet to go to the shop again.


Any idea what can be the issue? Could it be a thermostat issue? or some relay gone bad? I also checked the drawing at oriparts to see there is a thing called a pressure switch. Could that be the culprit?

https://oriparts.com/47/728/68141/2938715#item_62404304

I searched on this forum and found some threads where either the AC stopped cooling completely or where the cooling went for a toss in afternoon or after driving for some time, in my case the issue crops up even on a cold engine when switched on in the morning (guess the temp of around 35C in the morning these days is cold for an engine). For the short duration when the compressor is on, it does its work and the pipes and the air from the vents gets a little cool.
So my problem is diffrent from:

https://www.team-bhp.com/forum/techn...utch-coil.html (City GXi - AC Compressor clutch coil)

Last edited by guptavis : 10th June 2022 at 10:08.
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Old 10th June 2022, 10:23   #2
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

There are a couple of things that can cause this, some of them can be checked easily

Make sure the cabin filter is not clogged, also check the air inlets to the cabin filter for debris,leaves etc.

Check the condensors isn’t clogged.

A dirty/ clogged evaporator can cause similar behaviour. Not sure how easy it is to get access to. In many cars that is a dashboard out job, although you might be able to get a peek at it via other means.


https://www.wheelsjoint.com/honda-ci...how-to-fix-it/

Good luck

Jeroen
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Old 10th June 2022, 10:52   #3
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by Jeroen View Post
There are a couple of things that can cause this, some of them can be checked easily

Make sure the cabin filter is not clogged, also check the air inlets to the cabin filter for debris,leaves etc.

Check the condensors isn’t clogged.

A dirty/ clogged evaporator can cause similar behaviour. Not sure how easy it is to get access to. In many cars that is a dashboard out job, although you might be able to get a peek at it via other means.


https://www.wheelsjoint.com/honda-ci...how-to-fix-it/

Thanks for the quick reply Jeroen.

This car does not have a cabin filter from factory. I have confirmed this from various forums and from the Honda A.S.S. One needs to cut up the blower case to add one. I did not want to do that so its been running without a cabin filter.




I did spray the condensor with water. I do this occasionally. It appears to be ok, atleast not badly clogged/dirty from outside.

The evaporator is difficult to access. I could not get a view of it from under the dashboard or after removing the glovebox. If the issue is the clogged evaporator, i understand it may cause iceing on the evaporator and cause the compressor to switch off but would it not take a substantial time to switch back on? would it switch on again within seconds? It takes maybe 5-10 seconds in each off/on state

Last edited by guptavis : 10th June 2022 at 10:54.
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Old 10th June 2022, 11:25   #4
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by guptavis View Post
Thanks for the quick reply Jeroen.

This car does not have a cabin filter from factory. I have confirmed this from various forums and from the Honda A.S.S. One needs to cut up the blower case to add one. I did not want to do that so its been running without a cabin filter.
https://Youtu.be/d_x87cPgELQ


The evaporator is difficult to access. I could not get a view of it from under the dashboard or after removing the glovebox. If the issue is the clogged evaporator, i understand it may cause iceing on the evaporator and cause the compressor to switch off but would it not take a substantial time to switch back on? would it switch on again within seconds? It takes maybe 5-10 seconds in each off/on state
Can you check where the cabin air is drawn in and ensure there is no debris or leaves blocking the flow of air entering.

Yes, a clogged evaporator might cause icing of the evaporator, but in that case it is most likely the proper functioning of the system is also affected up stream, I.e. the expansion valve. I donít see an expansion valve in the drawing?

It appears your pressure switch is a dual action, meaning it detects both lo and hi pressure. Which most likely means itís actually some sort of linear signal input to whichever computer controls the AC. So, yes a defective pressure switch might cause the problem. On some cars the proper working of this switch can be measured with a proper OBD scanner with so called live functions.

As you mentioned, the most common reason for Compressor cycling is low refrigerant. Those pressure reading seem ok. If everything else seems ok, I would start to suspect the expansion valves and or pressure switch.

You might just want to check all fuses too. Check your manual if there are any relais labelled AC or compressor. You can just swap identical relais and see what happens.

Not sure what type of AC compressor your car has? Is it just one with only a magnetic clutch or a variable one?

Magnetic clutches sometimes go wonky. They switch on and then, usually due to old age, the resistance goes up sharply as they warm up. Which causes the clutch to disengage.

Good luck, let us know what they find
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Old 10th June 2022, 15:06   #5
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

I had a similar issue with my DZire recently. Trying to isolate components one by one, here's what was done overall:
  • Serviced the AC Belt Pulley as the bearing was offering some resistance - it actually started with a squealing noise from the belt, ultimately leading to the shredding of the belt.
  • Changed the Magnet assembly in the Magnetic Clutch - with age and higher temperatures, the effectiveness of this part decreases.
  • Cleaned the Radiator - with reduced running during the lockdown, gunk had settled in the radiator leading to reduced circulation of coolant.
  • Cleaned the AC Evaporator/Condensor fins with pressurised water at a service station. A cleaner/breathing engine bay is a good way to allow more surface area for the engine to vent out temperatures.

If the above list has not been touched in your car, its a good place to start off with.
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Old 10th June 2022, 17:42   #6
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

May be check the fuse / relay once? If they're alright, then check on the AC clutch if it's okay?
Not sure if something causing the AC to trip would be caught in the OBD scan (if it's engine overheating, I think it should be caught).
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Old 10th June 2022, 19:48   #7
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

For me this seems to be an issue with AC starter relay making intermittent contacts. Please start by checking the power input to AC circuit and identify the problem.
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Old 10th June 2022, 19:57   #8
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by guptavis View Post
...Honda City ZX 2006 which has done 1,03,xxx KM.
...I observed that the AC compressor started and then stopped within maybe 5 seconds and then started within 5 seconds and so on.
...
He connected a gauge to the low pressure valve and got a reading around 50psi when the compressor had been off and it went to around 30psi once the AC was switched on and started short cycling. He said the refrigerant is not low.
...
Any idea what can be the issue?
The system appears to be low on gas, but the AC technician doesn't seem to know his stuff. With adequate refrigerant, the low pressure end should be in the region of 50-55 psi while the compressor is running, and the high pressure end should show ~280-330 psi when the outside ambient temperature is 35-38 degrees C. Look up any car AC temperature-pressure chart on the Internet.

I would also suspect a leaking cooling coil, considering the car is 16 years old and had never had the cooling coil opened up / changed in all these years.

Find yourself another AC workshop in your city.

Last edited by SS-Traveller : 10th June 2022 at 20:04.
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Old 10th June 2022, 20:27   #9
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by SS-Traveller View Post
The system appears lowgas, but the AC technician doesn't seem to know his stuff. With adequaterefrigerant, the low pressure end should be in the region of 50-55 psi while the compressor is running, and the high pressure end should show ~280-330 psi when the outside ambient temperature is 35-38 degrees C. Look up any car AC temperature-pressure chart on the Internet.
You are correct on those values of course. But I donít think he ever measured the high pressure.

It said
Quote:
He connected a gauge to the low pressure valve and got a reading around 50psi when the compressor had been off and it went to around 30psi once the AC was switched on and started short cycling
So I read this as a measurement on the link Port only whilst Compressor off and on

Better check those measurements again

Jeroen
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Old 11th June 2022, 13:35   #10
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re: Honda City AC short-cycling | Compressor turning on and off within seconds

This does look like an issue around the cooling coil. Considering the age of the car, I would suggest you replace it and not just clean it.
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Old 15th June 2022, 16:51   #11
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Re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by guptavis View Post
Hi all,

I have a Honda City ZX 2006 which has done 1,03,xxx KM..
A few days ago I observed that the AC compressor started and then stopped within maybe 5 seconds and then started within 5 seconds and so on.I searched on the internet and found low AC refrigerant to be a common cause for this.

He connected a gauge to the low pressure valve and got a reading around 50psi when the compressor had been off and it went to around 30psi once the AC was switched on and started short cycling.

Any idea what can be the issue? Could it be a thermostat issue? or some relay gone bad? I also checked the drawing at oriparts to see there is a thing called a pressure switch. Could that be the culprit?
For the short duration when the compressor is on, it does its work and the pipes and the air from the vents gets a little cool.
So my problem is diffrent.
Firstly, to be on the same page, let's agree that the main problem here is that the compressor is cycling ON And OFF. Not intermittently or erratically, but at almost regular intervals. This tells us many things about the possible causes and trouble spots possible to look out for.
As per the points from your post that I have highlighted in my reply, I would like to state that, firstly, THIS PROBLEM IS NOT CAUSED BY LESS OR LOW REFRIGERANT. PERIOD.

This problem is most probably caused by high pressure in the system causing premature cut-off issue. Probable causes:
1) Condensor fan malfunction,
2) Radiator clogged/obstructed,
3)Compressor internally jammed
4)Expansion valve stuck shut.
These are the probable causes I can think off according to the scenario.

And I will say again, because most people found the fault to be Low Refrigerant, that if it's indeed the case of low refrigerant then the Compressor will either stay OFF, because the pressure switch doesn't allow it to switch on at that particular pressure range, or it will stay ON because the pressure is enough for it to stay on and in this case it won't shut off because it won't reach the cooling temperature point enough to cut off. But, IT WON'T CYCLE ON AND OFF!! I guess most mechanics get smart and use the "Low Refrigerant" diagnosis so that they get to fill the "Low" gas up and make a fast one. It's common.

Keep is updated on what you find.
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Old 17th June 2022, 21:53   #12
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Re: Honda City AC short-cycling | Compressor turning on and off within seconds

Quote:
Originally Posted by guptavis View Post
Hi all,

I have a Honda City ZX 2006 which has done 1,03,xxx KM.
Its been running flawlessly for the last 15 years and regular engine oil and filter changes are done.
Nothing much has gone wrong with it and its been reliable and refined all through.
A few days ago I observed that the AC compressor started and then stopped within maybe 5 seconds and then started within 5 seconds and so on. The air from the vents was only slightly cool and was basically useless in this summer heat. I checked by hand and found the suction pipe got cool and the condenser pipe got hot when the AC keeps cycling like this. I searched on the internet and found low AC refrigerant to be a common cause for this.
Check Radiator Fan before anything else.

Mod Note: Please quote ONLY the relevant bits of a post. Quoting a full, long post inconveniences our mobile readers.

Last edited by Rudra Sen : 17th June 2022 at 22:45.
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