air con system questions

air con system questions

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Chimp871

Original Poster:

837 posts

116 months

Monday 12th February 2018
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since I got my cerb the belt hasn't been connected up. The pulley spins freely and have yet to test if compressor, condenser, dryer, evap etc are working as they should.

There's a reason it's not connected and wondered what were the common faults on the air con system to save time?

FarmyardPants

4,099 posts

217 months

Monday 12th February 2018
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The condenser is in front of the water radiator and can be damaged by stones and road debris, maybe the a/c was disconnected because of a leak there? It is a bit of a pain to get to/change. If so, you may need a new dryer as well, although I am not an a/c expert so best get one in to have a look obviously.

Byker28i

58,831 posts

216 months

Monday 12th February 2018
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Have fun. I chased small leaks for ten years until I got mine to work.

Jimm218

200 posts

173 months

Tuesday 13th February 2018
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I have mine apart at the moment. So far I have found the compressor has a crack all the way up the underside and the hoses up to the compressor have worn through. I'm hoping that will be it but it will be a little while before I'm ready to put it altogether and test it.

Good luck.

Chimp871

Original Poster:

837 posts

116 months

Tuesday 13th February 2018
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So plenty of different issues then. The compressor is the big due to its cost so am thinking I'll put on a belt (5pk1113 I believe), re-gas and tested properly and look for leaks.

Assume there's no quicker way?

TwinKam

2,937 posts

94 months

Tuesday 13th February 2018
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A decent Aircon place wont regas your system with refrigerant until they have leak-tested the system with nitrogen. This is a legal requirement (often ignored) but also saves you money if you have one or more faults in the system, which you may well have.
By 'decent' I mean an experienced AC specialist, not a fast-fit monkey who had 2 hours training and is trying to do 12 regases a day to get his bonus.

nawarne

3,088 posts

259 months

Tuesday 13th February 2018
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TwinKam said:
A decent Aircon place wont regas your system with refrigerant until they have leak-tested the system with nitrogen. This is a legal requirement (often ignored) but also saves you money if you have one or more faults in the system, which you may well have.
By 'decent' I mean an experienced AC specialist, not a fast-fit monkey who had 2 hours training and is trying to do 12 regases a day to get his bonus.
^^I'd agree with TK, a pukka air-con specialist wont just stick a new 'charge' of refrigerant in. However, I understand that the testing procedure is to pull a vacuum on the system - and check to see how long the system can hold a negative pressure. (I'd imagine Nitrogen would be difficult to remove entirely?)

I also believe that the new charge has a dye plus the compressor oil added to it to highlight any leak paths.

Nick

TwinKam

2,937 posts

94 months

Tuesday 13th February 2018
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Nitrogen (or another cheap and 'inert' gas) is used as the system needs to be 'full' of something in order to test the compressor's ability to compress a gas!
It is removed by 'vaccing' in exactly the same way as the atmo air is removed before the refrigerant is introduced.

Jimm218

200 posts

173 months

Tuesday 13th February 2018
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Or you can use an air compressor to charge the system and leak check. Your not supposed to do this as it adds water to the system (and possibly some oil) but if there is a leak it is open to atmosphere anyway... That's how I found my holes. I wouldn't do it that way with the new components in. According to my new compressor (which was 280 quid in case you need to know) instructions the system needs flushing (but not the compressor or receiver drier), vacuuming for 1 hour and then connecting up, leak checking and charging. I'm considering finding someone mobile to do this.

Chimp871

Original Poster:

837 posts

116 months

Tuesday 13th February 2018
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I've got an air compressor - do you connect to either hi or low port and what pressure do you go up to I can add an air reg to make sure it's not too much

Byker28i

58,831 posts

216 months

Tuesday 13th February 2018
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I just chased leaks. New air con rad early on in life but I could never hold refrigerant for longer than about a month. Even the schreider valves in the refil connections leaked slightly!

Before the engine was removed I'd had working aircon for about 6 months. However - when it gets really hot, in traffic on a hot day, the aircon doesn't blow cold, I guess through the design of a really hot radiator/engine next to the aircon rad?

Thunderroad

202 posts

121 months

Tuesday 13th February 2018
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Hi there,
“Oxygen Free Nitrogen” should be used to pressure test the refrigerant system not air. Air will introduce moisture to the system which could freeze within the system and create blockages. But this is probably not something you would have readily available.

I would first find both Low pressure and high pressure test points and establish if there is any gas currently in the system by pushing in the schroeder valve and seeing if any gas comes out.

If you get gas coming out then i would assume there are no major leaks and buy a can of a/c gas from Halfords ready to top up the system if necessary.

You should be able to turn the compressor by hand, its not easy to turn but you should be able to do it. (Not the belt pulley, the bit on the front of the compressor) if you cant, it may be seized!

If the compressor is free to turn, and you have pressure in the refrigerant system, try to run it just to prove it runs, you should also be able to run it with no gas in the system, for a short period without doing any damage. (Assuming there is no “low pressure trip” on your system).

HTH.
Simon.


alabbasi

2,469 posts

86 months

Tuesday 13th February 2018
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If the belt isn't connected I would suspect that the compressor might be locked up which would still allow the pulley to spin as long as the clutch is not engaged. The first thing I would do is put gauges on it on and see if you have refrigerant in the system. If you do, throw on a belt , turn on the a/c and see what happens, while being ready to shut it down,

The next step would be to charge the system and add leak dye to see where it comes out.

Is your system an R12 or R134a system?

Chimp871

Original Poster:

837 posts

116 months

Wednesday 14th February 2018
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Thanks gents. I'll have a go at turning the clutch.

It's a weird quick connect coupling that I don't have otherwise I'd throw a gauge on. Let's see if the mechanics work first.

Thunderroad

202 posts

121 months

Wednesday 14th February 2018
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Not cheap, but it looks like the gauge and connection is re-usable. Handy to have in the garage due to most systems needing a top up every year. smile

alabbasi

2,469 posts

86 months

Wednesday 14th February 2018
quotequote all
Thunderroad said:


Not cheap, but it looks like the gauge and connection is re-usable. Handy to have in the garage due to most systems needing a top up every year. smile
Those things are pretty useless. Get a real set of gauges and learn how to use them.

Chimp871

Original Poster:

837 posts

116 months

Wednesday 14th February 2018
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So the clutch turns nice and freely with little resistance. I can feel it grabbing slightly as it passes the ports. Good news at this stage.

I'll hook up the belt & pulley and see what we get. If nothing then I'll find a decent air con place and get them to test it for pressure and leaks.


Thunderroad

202 posts

121 months

Wednesday 14th February 2018
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alabbasi said:
Thunderroad said:


Not cheap, but it looks like the gauge and connection is re-usable. Handy to have in the garage due to most systems needing a top up every year. smile
Those things are pretty useless. Get a real set of gauges and learn how to use them.
Hi Alibbasi,
Thats a shame, in what way are they useless? I have never actually used one of these as i have my own gauges etc. I just thought they would be a good thing for a DIY’er to have and save a bit of money. A proper gauge set etc is an expensive outlay if your only going to use them occasionally.
Regards, Simon.

alabbasi

2,469 posts

86 months

Wednesday 14th February 2018
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Thunderroad said:
Hi Alibbasi,
Thats a shame, in what way are they useless? I have never actually used one of these as i have my own gauges etc. I just thought they would be a good thing for a DIY’er to have and save a bit of money. A proper gauge set etc is an expensive outlay if your only going to use them occasionally.
Regards, Simon.
You can't really measure system pressure on the suction side (low side) and get a good idea of how full or empty a system is. You really need to measure the high side. A proper gauge set can be found on Amazon for about that price and will allow you to read both high and low side which will allow you to accurately (as accurate as you can get through charging by pressure) charge the system plus diagnose faults such as a worn out compressor, blocked expansion valve etc.

Haynes has a great A/C manual that you can buy which will teach you how to use the gauges.

Thunderroad

202 posts

121 months

Saturday 17th February 2018
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alabbasi said:
You can't really measure system pressure on the suction side (low side) and get a good idea of how full or empty a system is. You really need to measure the high side. A proper gauge set can be found on Amazon for about that price and will allow you to read both high and low side which will allow you to accurately (as accurate as you can get through charging by pressure) charge the system plus diagnose faults such as a worn out compressor, blocked expansion valve etc.

Haynes has a great A/C manual that you can buy which will teach you how to use the gauges.
The pressure measured on the discharge side cannot be relied upon to tell you how full or empty a system is either. (If the condenser is blocked the discharge pressure could be too high with an undercharged system) The only way to be sure the charge is correct would be either to reclaim the existing gas in the system into a reclaim cylinder and weighing the gas you get out using scales, or to start from a fully vacuumed system and weigh the gas in.

To do all this the diy’er would need to invest quite a bit of money on additional kit. Yes, you can get a cheap gaugeset from Amazon (but personally i wouldnt like to be stood around them for too long with 15 to 20 bar of pressure in them).

Personally, if i was’nt in the trade, and have the kit already, this can of gas with the charging hose on it would be axactly the sort of thing i would use.
If the system is empty just connect it up and purge the system for a few seconds to expel any air, then empty the whole can into the system, run the system to suck out all the gas in the can, i think the cerb a/c takes 1.5 kg so you would have to top up with another bottle using a set of kitchen scales (preferably digital for accuracy) job done!

Then turn the engine off and have a listen around the system for any leaks, then when the engine is cool, spray system with soapy water to check for any smaller leaks.

If the a/c still doesn’t work you could check your superheat but anything more than that you would probably be better off getting a reliable professional in to sort it.
That Haynes a/c manual sounds like it would be a handy point of reference thumbup