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Morning All - Hope everyone had a good Christmas!

I’m trying to sort the air conditioning on our 2002 Vogue SE at the moment. The last VSE I did wasn’t too bad but this one’s being a pain!

So far I’ve replaced:

Air Con Condenser
Air Con Drier
Pressure Switch
Tri-Switch
Both A/C pipes that run along the bulkhead
Various O-Rings

After doing all of the above I put 2 bar of Nitrogen into the system and soaked all of the connections with soapy water and got no bubbles anywhere. I then took the pressure up to 10 bar and after an hour I’d lost 1 bar of pressure. Over 24hrs I’m loosing anywhere between 6 and 8 bar of pressure in it.

I’ve done soapy water tests over and over on all of the connections that I can see and am unable to find any leaks anywhere. I’ve got the dash out just now replacing the heater matrix so I’ve sprayed the evaporator too and cannot see or hear any leaks anywhere.

I’ve bought some UV dye but as there’s zero refrigerant in the system I’m unsure how to circulate it as I don’t fancy trying to engage the compressor when it’s only nitrogen in the system.

Has anyone got any thoughts or suggestions on where to go next as I’m at a loss unfortunately.

Thanks,
David.

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Running the compressor with no refrigerant in it won't move the UV dye about, as the refrigerant is what carries the oil (with the dye in it) around the system. Nitrogen won't move the oil.

Are you sure you're service fittings aren't leaking? Might not have a complete seal on the quick release fittings. You could try putting a bit of pag oil on the o-rings in those, or around the outside of the connections on the car that they clip onto.

Might even be the compressor seals - more so if it hasn't actually been operated for a long time. They may sort themselves out once it has run with gas in it for a while - but unfortunately the only way really to find out is to get it filled up and cross your fingers. Or - find an independant mobile AC guy that is willing to fill it with gas and dye, run it for a bit, then recover the gas again assuming it makes itself known either via a good leak detector or visible UV dye.

Technically its not legal to fill a system you know is leaking here in the UK, but its not like that stops anyone. Not that I condone it - and gas is damned expensive! But in this case - I'd have no problem doing the above as a last resort to finding the leak. Better fill, lose a tiny bit finding the leak, and then recover the rest to repair, than just blindly fill it and send it when it may dump it all out in short order.

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One other thing I’m pondering the idea of is filling it with something that could be sniffed with a gas sniffer and then flushing it with compressed air and nitrogen.

We’ve got a sniffer and it’ll detect very small leaks but am not sure it’s a great idea.

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The other option was one of these:

https://www.pce-instruments.com/english/index.htm?id=google-uk&_artnr=271331&_p=170.4&_pmode=0&_pbexkey=37&_date=20211227011124&_pbhash=b31dd49355ae96eb15c7f1b79c878fab00831b42229b6f4da37f421a5f07f95c&gclid=CjwKCAiAiKuOBhBQEiwAId_sK2WAOy5hPX2pyyqqH4Jghqwrr1BLNaTp4EIyTlcLQQJ2EoOAFRzY4BoCgJ4QAvD_BwE

And a can of refrigerant from Halfords in the hope that it’ll be enough to allow it to engage the compressor, circulate the dye and then allow us two attempts with an R134a sniffer and the UV dye.

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A mate who does mobile air con work bought one of those and it found leaks everywhere. Then we realised is was responding to coolant, brake fluid, exhaust fumes and just about anything else it could sniff.

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I've got a Fieldpiece infrared leak detector - its been very good so far. But they're considerably more expensive than the heated diode type.

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Sounds like you have done everything up to the evaporator. Do you know what condition it is in, with its attendant connections?

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I’m following this to try and learn as usual, and won’t stray too far away with this question I hope: a/c wasn’t a big priority for me after getting the car, and I suspect the system was empty, possibly for some time.

I am in touch with a local a/c guy who’ll come and check out the system once the car’s back on the road. When I confirmed the system was empty, I did change the condenser when I did the heads and camshaft and added up dyed lubricant as advised by the a/c guy.

But would a compressor be damaged or need replaced if the system has had no coolant?

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donmacn wrote:

I’m following this to try and learn as usual, and won’t stray too far away with this question I hope: a/c wasn’t a big priority for me after getting the car, and I suspect the system was empty, possibly for some time.

I am in touch with a local a/c guy who’ll come and check out the system once the car’s back on the road. When I confirmed the system was empty, I did change the condenser when I did the heads and camshaft and added up dyed lubricant as advised by the a/c guy.

But would a compressor be damaged or need replaced if the system has had no coolant?

The worst thing generally for an A/C system is moisture - I've seen it ruin a compressor but that system had a hole in the pipework that had been present for several years. There is a dessiciant canister in the system which can capture moisture, but obviously it has a limit on how much.

When you regas it will first vaccum the system and then try to hold that vacuum, this should show up any obvious leaks and should get rid of anything in the system that isn't wanted to a degree (moisture should boil off with the reduced pressure AFAIK).

The system shouldn't try to run with too low charge so shouldn't be any reason to suspect the compressor of damage, and theres very little way to tell without trying to put refrigerant in and see if it works.

I've had a system sit empty for a year or so with no charge and got it to charge sucessfully once we found the leak (someone elses badly refitted pipe with a trapped o-ring) and its been fine since. You could get a nitrogen test done to test for leaks as detailed above if you weren't sure.

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Excellent, thanks Brian. I’ve no reason to suspect moisture having got in, so fingers crossed the system will have shut off as you’ve said. Sorry for the wee hijack O/P.

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If refrigerant has leaked out, moisture will have gotten in - the desiccant in the drier is there to absorb moisture in a closed system, so as soon as there is a way for more of it to get in, it will absorb all it can until it is saturated. That's why you should always replace the drier unit on any mobile AC system (or any refrigeration system that otherwise has one) when it has had work done to it - and I'd do it on any system that has sat with no charge in it for some time.

Some manufacturers have started using condensers with the drier element actually attached to them - given the condenser is the bit that cops the most abuse requiring replacement, it makes sense to package them together, protecting the rest of the system down the line.

Moisture reacts with the oil and turns it acidic - this in turn corrodes the system from the inside out.

Vacuuming the system down won't boil the moisture out of the desiccant unfortunately.

Re. the evaporator - it could be the source of the leak, but if you've checked that and can't find visible leaks on it, the only other place that is less easy to get to is the expansion valve block that lives between the firewall side of the evap and the pipe connections in the engine bay. It is removable and has two o-rings between it and the actual evap core - without taking it apart or removing the firewall foam around it, I don't think it is really possible to get an eye on it really.

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Had another look at this yesterday, I definitely can’t find any leak with soapy water and 10 bar of nitrogen in it so I’m going to need to look at getting some R134a and some UV dye into it.

I’ve got the UV dye so am thinking of buying a tub of refrigerant from Halfords to get the compressor to kick in and circulate the dye and then looking around the whole system with the UV torch now as I’m all out of ideas.

Thankfully the dashboard is out of this one just now as I’m doing the heater matrix (again!) and until I’ve found the leak I don’t really want to build it back up in case it’s the evaporator.

David.

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This afternoon we managed to find the leak in the Air Con system thankfully.

enter image description here

The soapy water spray was running off the compressor to quickly so we weren’t seeing the bubbles. We got some leak detecting spray today that was much thicker and didn’t run off so quickly and we found this!

https://youtu.be/bxO7aPl3jjQ

Going to order a new compressor and get it fitted then hopefully that’s another part of this P38 back to working condition.

David.

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Nicely done!

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Did well there! Imagine if the leak were not on a visible side of the compressor, in that situation I'd probably keep looking around other parts for ages before thinking about replacing the compressor.

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I’ve been looking around it for days and was about to throw in the towel when I just happened to glance and see that. Quite lucky really as I was loosing the will to live.