Weird AC Problem hot-cold-hot-cold

Good afternoon,

My 2.0 tourer has developed a strange air conditioning problem that has people scratching their heads.

Basically the air conditioning works beautifully, but only for a short period of time and only when the engines revs are up above about 3500rpm.

If you turn the car on at tickover and turn it to LO, it will not work. Get driving and get the revs above 3500rpm roughly, beautiful cold air will start firing out.

Cruising at 80mph, and you will noticably feel the compressor cutting in and out with a corresponding change in temperature. Gas is fully charged, relays were changed for brand new Honda items.

I am at a loss!

Any words of advice? I tried the DIY AC diagnostics, but I wasn't entirely sure what the readings should be if the system is working perfectly. Nothing seemed amiss.

that description sounds like a perished condenser, with a perished condenser the system runs colder at higher road speeds (not engine revs, just road speed)

After having inspected the condenser, it is not perished at all. 99% of the fins are still there and in-place, a few are squashed as you would expect and some dead flies packed in there.

But it also wouldn't explain why I can noticably feel the compressor cutting in and out at a steady throttle position at 80mph. At which point ice-cold air immediately starts coming out the vents, or when it cuts out the air starts getting warmer as if the A/C isn't functioning at all.

Also, if I accelerate to 40mph in second gear with high revs after pootling along, the ice cold air will start coming through. Go to fifth gear at the same speed and it will either stop or won't cut in at all if getting to that gear/speed from rest.

Really irritated with it!

freddofrog said:

This was the condenser on my car before I replaced it, front bumper removed.

Click on picture to enlarge the picture, then you can see the difference between the top half of the condenser (above the front spar), and the bottom half of the condenser (below the front spar)

Click to expand...

For example, the bottom of my condensor look as good - if not better - than the top of yours!

this is the condenser in the car




same one when out of the car






another perished condenser out of the car









as you can see, they don't have to look as bad as the one that was in my car, basically it's not so important what the condenser looks like in the car, it's what it looks like when it's taken out



Those symptoms definitely suggest perished condenser, the only other things could be low on gas, or slipping clutch on the compressor, but if it was either of those then coldness would be related to engine revs only, road speed would make no difference. Higher road speeds give better cooling to the condenser, if the condenser is perished, it needs more air flow than the fans can provide.


btw compressor cutting in and out is normal operation when the gas is compressing to liquid and back to gas during the heat circulation.

Definitely a perished condenser problem and I would also change the receiver drier when doing it.

One thing you can try is to get a hosepipe and run cold water over/down the condenser while the engine is running with the A/C on, but you'll have to remove the grille cover/trim above the condenser to get the water onto the condenser (if you do remove the cover/trim, make a note of which trim-clip goes into which hole, they are different lengths).
If the A/C does not blow cold like that then take the car to an aircon specialist.