Weak air con

[GavinC]

My '95 960's air con (manual system, not climate control) is not blowing as cold as I remember it could and when the engine is under load - pulling uphill - the a/c ceases blowing altogether. Then resumes as load lightens. Also, the 'face-level' dial setting for the vents always exhibits a quiet, barely audible 'hissing' noise that is not apparent on the other vent settings. As if it's got a restriction or a small leak...However the air con does not appear to perform any better on any of the other vent settings, either.
Are these symptoms related to a single underlying cause? Also, I'm thinking that if the air con gas is low, might that cause the system to break down entirely? Unless I get it recharged irrespective of whether I use it all that much over the coming cooler months. Even so, I'm under the impression that air con should be used at least once a week for 15 minutes or so, even in the winter, so the seals maintain their condition. That has been my practice, anyway. Is that correct practice? Honest John - the Telegraph motoring columnist - says that for system life air con should be always 'on' even if not set to 'really cold' and fuel penalties vary depending on the make and size of car. Interestingly, he said that on a larger Volvo he ran the fuel penalty was negligible. Any advice/comments would be much appreciated - thank you.

Hi,
Just going through aircon rebuild at the moment so have some thoughts to contribute.
My aircon pump solenoid clutch burnt out. Fitted a scrapper (nasty job and could never get the rear support bracket completely off or back on). There are 4 moutnign holes BTW and you need to be Houdini to get at all of these with the engine on it's mounts.
Had system recharged, ran fine for 1 hour then the clucth started slipping and we think the scrap pump is duff.

Lessons I have learnt:
1.You should always change the receiver/filter (big aluminium pot that gets cold on the bulkead) when you change a pump.
2. If you buy a scrap pump it'll cost you approx GBP100 to charge and bleed down if it is duff.
3. It'll take you about 4 hours to change the pump.
4. Skip the above and go to a specialist to save marriage :-)

I use Azure in Basingstoke. He can get sensible prices on new pumps etc or can have them remanufactured (not recon'ed).

Things you could check.
Is the solenoid clutch engaging when you switch on the aircon (clunk)?
Does it stay on until the clunck off or does it slip (bad smell)
Does the aircon light on the ECC show a fault code?
Does the disgnostic port under the bonnet provide any fault codes?
Does the receiver/filter actually get cold?
Anything to suggest that the vents are not being actuated when you change the vent options (bad solder joints on my 760 in the vacuum controller under the dash meant the vents were all shut down so not much air flowed except to your feet)?
Does the hissibng stop when you bypass the aircon?


Sorry for such a long posting :-)

I too follow the HJ code, never tried the 960 without the aircon running though. Had a diesel Rover that returned better MPG with aircon ON.

G


1995 facelift 960 Auto Estate 3.0 24v, 136K, 3 years with me. Changed: self level rear shocks '05, front susp bushes '05, air mass sensor '04, lambda sensor '04, Gear selector switch '03, disks/pads '03

[GavinC]

Many thanks for your detailed reply and check-list.
The receiver/filter clutch appears to engage and disengage as normal. The receiver/filter gets cold as do the pipes associated with it - condensation forms on them as I'd expect. The barely audible hissing related to the face-level setting remains when the a/c is 'off'. (Possibly a leaking air-line?? Or a flap not fully open?? I don't know...just guessing :-)) The fault codes I haven't been able to check - I'd need the appropriate tool.

My research suggests that it is normal that - on acceleration or pulling uphill - the cool air appears to switch 'off' as the vacuum system 'compensates'and the a/c compressor shuts down to allow a couple more horses to be available to the engine. My a/c (it's not climate control) is noticeably cool but never 'cold' even on full blast... and cabin temp. feels pretty much the same whatever the vent setting. On a really hot day it is just cool enough even on fan setting '4' and turned to max. cold.

I am now wondering - hissing face level vent aside - whether it is simply low on gas. Although no oily residue suggesting a leak is apparent...at least from what I can see under the bonnet. P'raps a tiny leak somewhere...p'raps dye would reveal??? I dunno... If the system simply requires a little maintenance or a regas to keep it and the seals in good nick - I wouldn't want to let it die.

To that extent I've found that Halfords have a couple of varieties of DIY regas and maintenance kits including system lubricant, seals conditioner and 'small leaks sealer' all-in for around £30. I'm wondering if it's worth a try?? Has anyone had any experience with that? Would that product, in fact, satisfy the full maintenance requirement to keep my a/c in good working order? Or, is an a/c 'specialist' likely to be better value? Nevertheless, the product's instructions say I need to fit the filling device to the a/c's system's low pressure port. There's a black plastic cap designed to take a spanner near the receiver...is that it? Where is it?? Any tips, further comments/advice would be much appreciated.

[Mike Arnold]

Another indicator of low gas is rapid cycling. On a moderate to warm day the pump should pull in and stay running for, say, 20s to a minute before clicking off. If it is clicking in and out every 5 secs then probably low gas.

On a very cold day it is normal to cycle fast even when fully gassed.

[terry_cunnane]

Interesting thread this.
My a/c was recharged 18 months ago but only just maintains a cool atmosphere. It does have climate control and is a 3 litre engine (1995 model).
I went to Sri Lanka for the first time this year - never been to anywhere that hot! - and the a/c in the taxi/vans was much more powerful.
Do different markets have different a/c specifications according to their climates?

Terry

[GavinC]

Many thanks for your contributions. Sounds like low gas is at least part of the problem. The pump is cycling 'in' for just 5 seconds or so, then 'out' for 40ish. With cabin fan on lowest speed. There is a 'musty' odour in the cabin during the first couple of minutes of a/c operation, too - more noticeable after the car has been standing for a couple of days. I have read somewhere that R-134 has a tendency to leak/migrate slowly over time so that "in 3 years without a recharge it'd be not unexpected"??? to be down to 50%...I would guess, on the other hand, that it can only 'migrate' if there is a leak/component failure. To trace a leak at an 'a/c shop' must cost before any further work is done. I'd prefer to avoid unnecessarily chucking money away if I can - but I also try not to be 'penny-wise and pound foolish'...

So, has anyone an opinion on DIY gas recharge kits which include lubricant and small leak sealer such as available from Halford's? Or is that a cheap & nasty short term 'fix'? And where is the low-side port to recharge on a 960?

Also, should the receiver/drier be renewed as a matter of course as I have read elsewhere or is there a symptom that would indicate when this is truly necessary? (Other than known 'open air'.)

Finally, if I continue to run with low gas (say, till next summer) my research suggests that I jeopardise the system's components thru lack of lube. Excessive pump cycling can't be good, either. Am I right on both counts? And if I continue to run it with low gas if I judge a leak to be not worth fixing (so, ultimately go without the a/c) do I risk seizing components and will that 'knock-on' to any other non-a/c components? Accessory belt to p/steering...Surely the compressor will just 'free-wheel'?

Man, I have only just begun to appreciate the 'ins and outs' of a/c maintenance and repair. With some extensive research over the internet it seems a/c can be a troublesome minefield and components are expensive. Preventive maintenance and proper operation is ultimately - as always - the only answer. Any more answers/suggestions would be gratefully received. My budget is tight at the moment.