Car air-conditioning DIY repairs... can anyone on here advise me please?

[charlysays]

My old W202 Merc (1997) has AC but it hasn't worked for years and years. With summers seemingly ridiculously hot these days I'm considering getting it working again. Car runs on waste chip fat so I really don't care about the fuel economy much.
Can anyone advise what might be totally goosed and if so, how I can check these parts? I've been told the compressor and dryer are almost certainly knackered and possibly the condenser too. These parts are all available off autodoc although if I can get away with not changing them all that would be good.

For example, could I inspect the compressor to see if it's badly corroded interally?
If it's not maybe it's worth trying to use it?
Could I pressure test the system somehow using compressed air perhaps to test the condenser?
Assuming the compressor and condenser aren't obviously knackered, could I just replace the dryer and get the rest of the system flushed and recharged and give it a go?

I'm assuming I need to somehow find a way to flush the system and replenish with oil and refrigerant at the bare minimum, is there a way to do this DIY or do I need to find someone with an AC flushing/ recharge machine?
I've read you can flush with pure alcohol and you can recharge the oil and refrigerant using canisters from halfords etc.

Thanks in advance, appreciate it's a bit specialist what I'm asking but this forum never ceases to amaze me regarding expertise of members
Cheers

 

[bert]

Kwik fit offer money back if the recharge doesn't work so I'd just book it in and pay the £70. I did it Saturday, they didn't let it run long enough for the cold air to begin so refunded

Their machine will vacuum test before refilling

 

[charlysays]

Kwik fit offer money back if the recharge doesn't work so I'd just book it in and pay the £70. I did it Saturday, they didn't let it run long enough for the cold air to begin so refunded

Their machine will vacuum test before refilling

Just looked this up and seems like a good start thanks If no effective recharge then at least it'll be some free diagnostics.

 

[slim_boy_fat]

If it's been unused for so long I'd expect all the seals to have dried out, maybe @premmington or someone knowledgeable like him will know what's needed to bring the system back to life, if it's even possible?

 

[Ross365]

You expect sensible air-con diagnostics from the guys at Kwik Fit . The blind leading the blind!

I'm surprised if halfords are still selling gas kits. Only qualified people are legally able to work on air-con now because the gas is so bad for the environment. Legally, they cannot fill a system unless they have tested it in advance and found it leak-free.

 

[premmington]

You expect sensible air-con diagnostics from the guys at Kwik Fit . The blind leading the blind!

I'm surprised if halfords are still selling gas kits. Only qualified people are legally able to work on air-con now because the gas is so bad for the environment. Legally, they cannot fill a system unless they have tested it in advance and found it leak-free.

Even I had to get a Fgas ticket - even at my age - as long as I been doing it (was no aircon qualfications when I did an apprenticeship).

 

[Ubique]

F-Gas is just a refrigerant handling certificate to allow you to legally connect to AC systems, actual training on systems is completely different.
Back to the OP's issue, the first thing to do would be recover any refrigerant - if there is any then it would be a good assumption that the 'internals' are in a decent condition. If the system is just air, then TBH, you'd need to replace most if not all of the system due to contamination, condensation (in turn causing corrosion) and external corrosion (road salt vs. condenser).
If you're lucky enough to have some refrigerant in the system, then the next step is to find out why it stopped working in the first place, pressure switch/sensor and supply to compressor clutch would be the first places to check, if OK, and a pressure leak check is OK, you need to be checking the high & low pressures.

 

[charlysays]

You expect sensible air-con diagnostics from the guys at Kwik Fit . The blind leading the blind!

I'm surprised if halfords are still selling gas kits. Only qualified people are legally able to work on air-con now because the gas is so bad for the environment. Legally, they cannot fill a system unless they have tested it in advance and found it leak-free.

I did look up the law on this and it only mentions service providers with regards filling up AC systems which may be leaky. Last thing I want to do is pollute the environment though, so perhaps quik fit are a good first step as they legally aren't allowed to fill a leaky system, so they test it first, then fill it if it passes the test, but don't charge you anything if it ultimately doesn't work.
At that point I would probably ask them to drain the system fully, then I might look at replacing parts/ flushing out the lines etc myself before trying to charge it it again.

 

[steveo3002]

on the basis its broken and wont make it any worse try this

if its air tight then see if bridging the clutch relay will make it engage for a few seconds , then find somewhere to fill it

 

[charlysays]

on the basis its broken and wont make it any worse try this

if its air tight then see if bridging the clutch relay will make it engage for a few seconds , then find somewhere to fill it

Great video, thanks man. Good to see a video which gives decent DIY advice!

I think I'll take it to kwik fit first, nothing to lose trying their service tbh. If its dead or they won't even recharge it because of a leak I'll get them to discharge it fully, buy some chinese gauges like the ones in this video and get diagnosing/ replacing bits, then once I'm done maybe have another go with kwik fit or recharge myself with a halfords cylinder. Looks like even though I'm not doing any spray painting the minute, all that I invested in compressed air drying will come in handy if I tackle the AC issues on my car.