Citroen Dispatch - can't find leak

[oscar21]

Hi my name is Wayne and I'm having a few problems with my aircon on my van, if anyone can offer me any pointers I would be grateful. This is the sequence of events, we purchased the van about 12 months ago and all last summer the aircon worked perfectly, this year when it got a bit warmer it didn't work at all, I did a few preliminary checks and deduced there wasn't any pressure at all in the system.

I then took it to my local specialist and he did a vac test and a pressure test with nitrogen and it failed them both, all he could tell me was it was leaking somewhere and it could get very expensive to fix. He did suggest the condenser is a likely culprit so I took the vehicle back home and removed the condenser, I then pressure tested it on my bench and checked with soapy water, sure enough it had a small leak in it with the soap bubbling away. I ordered a new condenser and replaced it along with the o-rings for it.

I took it to one of those re-gas places offering a cheap re-fill with a voucher, they said they can't do it because its still leaking. I got them to pressure it up with nitrogen and drove it away. I then bought my own gauge set and vac pump from Amazon to see if I could find anything, checking the pressure with the gauge set it was bang on 90 psi a few days after he charged it up, I checked the next day and the needle was still exactly where it was so as far as I can see there is no leaks in the system. However if I do a vac test the gauge drops to near enough zero within 30 seconds, its not the gauge set because if I close the schrader valve knobs the vacuum holds.

So why would it be rock solid under pressure for days but lose a vacuum straight away? I don't get it, I left the pump running for about 45 minutes as well, it does initially drop down to about -28 on the gauge when you start the pump but as soon as you shut of the manifold valves it drops back down.

Thanks for reading, Wayne.

[JohnHere]

Good work finding the condenser leak and solving that problem.

You didn't give the vehicle's year, engine size, front and rear A/C or front only, and refrigerant type. It sounds like a European-spec vehicle, although you didn't say.

However if I do a vac test the gauge drops to near enough zero within 30 seconds, its not the gauge set because if I close the schrader valve knobs the vacuum holds. ...So why would it be rock solid under pressure for days but lose a vacuum straight away?

If you close both valves where the red and blue hoses connect to the vehicle's ports, then I think it is the manifold gauge set that's leaking someplace.

I don't get it, I left the pump running for about 45 minutes as well, it does initially drop down to about -28 on the gauge when you start the pump but as soon as you shut of the manifold valves it drops back down.

If you're at or near sea level, your vacuum pump should draw the system down to at least 29.9 inches of mercury (In. Hg.) If it only pulled down to 28 In. Hg. due to a leak in the manifold gauge set, it's probable that you still have some air and moisture in the system.

It sounds to me as if you don't have any more leaks in the system. At this point, I would ensure that all my gauge-set connections are tight (using a little Nylog Blue on all the rubber seals), change the receiver/dryer or accumulator, pull another vacuum on it for two or three hours, verify that the vacuum holds, then fully charge it to the exact amount using a refrigerant scale. I'm assuming that you can buy your own refrigerant in Europe. Add a little refrigerant oil to the receiver/dryer (maybe one ounce) before you install it, plus some UV dye (one ounce or less) in case you need to leak-check the system in the future. Then drive the vehicle to see whether the charge holds and it cools sufficiently.

[oscar21]

Yes, thanks for the reply, I'm from the UK. The vehicle is a 2015 van, front only aircon, quite a simple system really, the dryer is part of the new condenser.

When I first had it tested they pressurised it up to about 200 psi and it lost about 50 psi within 15-20 minutes, that's when I checked the condenser, I removed it from the vehicle and pressurised it up on my bench to find the leak, sure enough it leaked quite badly. its possible I caused the leak removing it but now with the new condenser fitted it doesn't seem to leak at all under pressure its unlikely. And because it was working fine last year its unlikely to have had two faults.


What I mean about the gauges is if they are isolated from the vehicle and I draw a vacuum - Schrader valves isolated but manifold valves open - the gauge holds steady when I turn the pump off, it stays at 30 no problems but when the vehicle is part of the circuit the vacuum drops away almost immediately.

We can buy gas in this Country but I don't think its official R134a gas, more likely a butane/propane mix, you have to be registered to buy the official stuff, however its on;y about $20 to buy enough to fill the system so its cheap enough to try.