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Working AC, at last!

To clarify - that's In Car Entertainment - not frozen water
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EddieMunster
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Working AC, at last!

Post by EddieMunster » Wed Feb 27, 2019 3:03 pm

Hi

I thought I'd post about the AC system, just to give other owners the heads up. My AC wasn't "working", so I had a re-gas specialist friend come and have a good look at the system for me and this is what we discovered.

1. The compressor will remain off when there's no gas in the system, or when there's low pressure. This is quite normal for cars from the 2000s onwards, but it's very, very unusual for a car from the early 90s. I mention this as my initial diagnosis was that the compressor itself was seized or faulty, whereas in reality the system could detect low pressure and the compressor had simply turned itself off.
2. The compressor doesn't affect the static revs as you'd expect; normally, you put the AC on and the revs immediately drop, but this isn't the case with the Honda. On most cars, when the revs don't drop you assume the compressor isn't engaging, but that's not the case here. It will kick in and out, but at normal idle speed the Honda compressor can still work and run the AC to around 9-10 degrees vent temperature.
3. The Honda AC system changed 6 times in the life of the 4g, almost every year, so that can mean fixing a non-working system could be tricky.
4. The Honda AC system takes 600g of gas, that's about 200g-300g more than a car of this age would normally take. Most modern systems only accept 120-150!!
5. The Honda AC system, when fully working, will get the vent temperature down to 3 degrees; that's very, very cold! Indeed. most modern systems will struggle to get to 9-10, and the very latest systems are between 12-13.
6. The Honda AC system will continually cycle, so you'll get 3-4 degrees for 10-15 seconds, the compressor will lift off and it'll rise to 8-9 at which point it'll kick in and go back down to 3-4. You don't feel this temperature rise in the cabin, it remains cold throughout.
7. There's a factory-fitted clip on the bottom left-hand side of the condensor radiator, as you're stood at the front of the car, and it's the SAME colour under UV light as the testing dye is! Initially, we thought there was a leak until we noticed that it was in fact a clip!

So, an hour spent today on the system means I have fully working ice-cold (and I mean ICE-COLD) air-conditioning.

Regards
4g 2.2 in Silver, 5g 2.2 Motegi in Blue.

Scott560
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Working AC, at last!

Post by Scott560 » Wed Feb 27, 2019 4:44 pm

I think the lower pressure sensor has been around for a while. I believe its also known as a trinary sensor (3 states, 4 pins) , and is essentially 3 pressure switches in one (low/ok/too high).

I had one on the Rover 620ti and that was a 94onwards car (mostly an accord, but the engine and management was a rover, so expect the loom was rover too).

Glads its sorted though. The revs may not drop instantly as the clutch will ease it in i believe, rather than a harsh jolt to the compressor and the belt drive.

Newer cars aircon is more complicated, emissions and all that - they are also much more efficient. Rather than cycling the aircon on and off, they have adjustable compressors so that they can always run the most efficiently.

Surprises me how many people you see with the aircon not running in winter months - little do they know it actually helps dry the car out, removes smells, and of course lubricates all the seals/components, and if you don't do that, they dry out and you lose the gas...
'00 UKDM 2.2VTI H22a8
'97 UKDM 2.2VTi (Gone)

EddieMunster
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Working AC, at last!

Post by EddieMunster » Wed Feb 27, 2019 5:18 pm

Scott560 wrote:
Wed Feb 27, 2019 4:44 pm
Surprises me how many people you see with the aircon not running in winter months - little do they know it actually helps dry the car out, removes smells, and of course lubricates all the seals/components, and if you don't do that, they dry out and you lose the gas...
In a car with as much glass as the Prelude, AC is more important in the winter/wetter months as it is in the summer months as it helps to keep the condensation to a minimum. My new Civic literally drips water from the windows on days with high humidity, the AC doesn't remove all of the condensation no matter what setting it's on or for how long you drive; I'm dreading the summer in it!

In contrast, the Prelude was on cold, fan speed 1, and after 5 minutes I had ice-cream headache!! :D
4g 2.2 in Silver, 5g 2.2 Motegi in Blue.

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