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Topic: Ineffective air con (Read 1197 times) |
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sector-9
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No scorpio anymore
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Ineffective air con
« on: Jul 3rd, 2006, 10:38pm » |
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Guys and gals, now I've decided to hang on to my Scorp a little while longer it's promptly thrown another wobbly!
This time the air conditioning seems very weak, though the compressor is turning normally and the cooling fans cut in and out as they should. The narrow high-pressure pipe going into the expansion valve is ice cold (quite literally, it is icing up!), yet the evap coils only get slightly cooler than ambient. Also the return low-pressure pipe is colder than the evap. As the compressor runs ok I don't think it is electrical, and because the fans run every few seconds that would imply enough system pressure to work. The air-con was regassed in March though the guy was in a hurry as I arrived near closing time!
Now I'm no expert on A/C systems, and certainly not when it comes to the plumbing side, but I suspect I have a problem with the expansion valve. Would anybody like to confirm this? If it is the valve, could it be fixed by having the system evacuated and regassed again (being as that'll need doing anyway if I have to replace it)? If not, can I fit a s/hand valve or are they best bought new and if so, how much are they?
As you can imagine, finding out how ineffective it is in this weather is far from ideal and I'd like to get it sorted ready for my holiday to the lakes in a fortnight. Local scrapyard has (had?) a Scorpio in which has CC fitted so I should be able to get the valve off that if it's worth the bother.
Darren
P.S.
ABS light has been off for a few days now, despite me driving through a ford several times to see if that would bring it back on.
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rwaircon
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Re: Ineffective air con
« Reply #1 on: Jul 4th, 2006, 7:47pm » |
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Hi
First, check that the cooling fans are working at normal speed, not full tilt all the time. if the fans are running full tilt then your problem could be a blocked reciever drier. If not then check the pollen filter isn't blocked(if it has one fitted) otherwise it seems that the expansion valve is shutting down too quickly( or it may be partially blocked).also check that the thermostat for the a/c is working correctly. Hope that this is of some help. 
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sector-9
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Re: Ineffective air con
« Reply #2 on: Jul 4th, 2006, 11:41pm » |
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Thanks for the reply, the fans only run at one speed but this is all the system fitted to my car is capable of. They do not run all the time but come on for about 3 seconds every 15 seconds or so (the condensor is hot). I have removed the pollen filters (I don't suffer from hay fever and they were disgusting anyway!). I don't think it is the thermostat as the compressor does not stop running as it would for the de-ice function.
Does the expansion valve need to be replaced or will vaccing the system be sufficient to unblock it? Hadn't thought about the receiver - can this be disconnected and drained out like you can do with compressed air receivers?
Darren
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Mickey_2.9
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Re: Ineffective air con
« Reply #3 on: Jul 5th, 2006, 1:06pm » |
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Darran,
I agree with rw that you may well need a new drier. If when you had the system recharged in March the guy was in a hurry he may not have vacuumed it down long enough for all the moisture to get boiled out if the system. If you have moisture in the system and the drier can no longer absorb it it will tend to freeze up the expansoin valve after only a short while of running.
If you get the drier changed make sure that when the system is vacummed down it is done so for at least 30 mins ( the moisture will boil away in a vacuum)and that the correct amount of oil is fiitted before the charge of R134a is added.
BTW you do need to get the system degassed before you change the drier.
Mickey
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sector-9
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Re: Ineffective air con
« Reply #4 on: Jul 5th, 2006, 10:42pm » |
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Cheers. Any idea how much they cost and is it a FMD only part?
Darren
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Mickey_2.9
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Re: Ineffective air con
« Reply #5 on: Jul 6th, 2006, 12:39pm » |
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on Jul 5th, 2006, 10:42pm, sector-9 wrote:Cheers. Any idea how much they cost and is it a FMD only part?
Darren |
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No but I can find out for you if you wish, what age and spec is your Scorp ?
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sector-9
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Re: Ineffective air con
« Reply #6 on: Jul 6th, 2006, 11:38pm » |
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1995 2.5TDi with SATC.
Darreh
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rwaircon
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Re: Ineffective air con
« Reply #7 on: Jul 7th, 2006, 8:25pm » |
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Darren
The drier costs about £40, there is a chioce of two,dependent on the bracket arrangement. Check that the a/c gets to the correct temp by turning the a/c on, fan speed 1 and the vents set to face. with this arrangement, you should see between 5 and 6 degrees at the vent and the a/c compressor should then disengage, it will then come back on when the temp reaches 8/10 degrees, if the temp goes below 2 degrees then the problem may be the frost sensor, if it fails to reach 5/6 degrees and starts freezing, then you will be looking at an expansion valve. all work to the a/c system requires the system to be de-gassed by an a/c specialist. if you have any more questions please ask
Robin
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sector-9
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Re: Ineffective air con
« Reply #8 on: Jul 8th, 2006, 1:57pm » |
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Well it went in for a regas again today - they said there was a small leak on an O ring on one of the drier connections which they replaced. They've also added some leak-detector dye and sealant.
Unfortunately the only difference I can feel is that my wallet is £50 lighter...
With the air-con running and the car in the shade the vent temps drop to about 12degC (not sure of ambient but guess 17-19). Driving along in the sunshine it barely keeps the car cool. When I got home I lifted the bonnet and saw that the high pressure pipe going into the valve had frosted over, and the low pressure pipe returning to the compressor was cool. However the evap still doesn't get very cold. I did unplug the blower motor with the a/c running and eventually the compressor stopped running (condensor fans off so presumably cut off by the de-ice circuit), but the evap still wasn't very cold.
Problem is I don't know how to test the expansion valve, but after reading up on what they do it would certainly seem like mine is stuck fairly well closed and only allowing a small amount of refrigerant into the evap (when the ambient temperature is low the vents do run quite cool). Unfortunately FMD want about £75 ex. VAT for one of these, plus the O rings and it'll need regassing again! Sod it, it can wait until after the MOT in October before I start spending any more money on it...
Darren
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rwaircon
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Re: Ineffective air con
« Reply #9 on: Jul 8th, 2006, 8:42pm » |
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Hi Darren
Where on the high pressure pipe is the frost. is it near the valve, if so check the end near the drierit should be quite warm, if it feels cool or cold then the problem is the drier.
Robin
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sector-9
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Re: Ineffective air con
« Reply #10 on: Jul 8th, 2006, 9:07pm » |
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The frost is near the valve, but the same pipe is still cold coming out of the drier (the pipe from the condensor is warmer). I take it you think there's a restriction in the outlet of the dryer causing the pressure drop (hence absorbing heat in the pipework).
Darren
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rwaircon
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Re: Ineffective air con
« Reply #11 on: Jul 9th, 2006, 1:45pm » |
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Darren,
the drier is blocked and requires replacement. do it sooner rather than later as you risk damage to the compressor(not enough oil getting back)
Robin
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mr._floppy
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Re: Ineffective air con
« Reply #12 on: Jul 9th, 2006, 5:02pm » |
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It does sound like the expansion valve isn't letting any, or very little, cool
stuff to the evap. There's seems to be no problem about producing
sufficient refrigerant ( which would be the case if the drier was knacked ), it
just ain't circulating properly.
You could try whacking the Expansion valve with a blunt instrument. 
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Mickey_2.9
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Re: Ineffective air con
« Reply #13 on: Jul 9th, 2006, 11:32pm » |
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Darran,
I would be inclined to disconnect the electric plug to the compressor and tie it out of the way untill you get the system repaired otherwise you may have to replace it when it burns out due to lack of lubrication, that in itself will open up a new can of worms if you get bits of burnt out compresor in the system.
Mickey
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rwaircon
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Re: Ineffective air con
« Reply #14 on: Jul 10th, 2006, 9:01pm » |
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with regard to the drier (re Mr floppy) if the drier gets blocked, it acts just like an expansion valve and drops the pressure in the wrong place- take it from an expert that knows what he is talking about 
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sector-9
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No scorpio anymore
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Re: Ineffective air con
« Reply #15 on: Jul 10th, 2006, 10:01pm » |
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Sorry guys, can't afford to replace the drier and regas again - in any case I don't really want to until it passes it's next MOT in October - could end up throwing good money after bad and the a/c has already cost me £100 in regassing alone. I can't disconnect the compressor clutch multiplug as I've superglued it in place (the clip had broke and it kept working loose), but I will pull out R24 which should stop it from running.
I can't comment on the state of the compressor as it is, but as the pressure builds up enough to bring in the condensor fans, and finally to stop the compressor if the fans don't run, I assume it is doing it's job adequately...
Thanks for all the help. If it goes through the MOT with little needed then I'll be looking to sort it around Christmas unless I fall into some money beforehand (unlikely).
Darren
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