Air direction problems

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jthorne
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Air direction problems

Postby jthorne » Fri Oct 21, 2011 7:51 pm

Hi,

My 1977 DD6 Coupe has A/C which works (well the clutch engages) but not too well as it isn't that cold...

However my main issue is that I can only seem to get cold air at my feet and hot air on the screen. The temp will vary but the placing of the air is always up towards the screen. There is no air blowing out of the centre vent. Is there anything I can do about this?

Many thanks

Jon
1977 Daimler Double Six Coupe

almcl
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Re: Air direction problems

Postby almcl » Sat Oct 22, 2011 7:50 am

The centre vent operates by vacuum but it only opens when the servo motor (on the back of the rh control) has moved more than half way to cold. (Diagram below)

If you can see the linkages moving or hear the servo turning when the temp knob is moved, it's more likely to be a vacuum issue. The pipes can come away particularly where the rubber elbows connect, under the crash roll.
Attachments
vac diagram.jpg
where the vacuum hoses go
Delanair Mk II.jpg
what happens as the servo rotates
Al McL
'93 XJS 4.0 - '05 X type Est 2.0D - '13 XF 2.2D Sportbrake

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jthorne
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Re: Air direction problems

Postby jthorne » Sat Oct 22, 2011 8:11 pm

Thanks for this will look into it.....
1977 Daimler Double Six Coupe

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jthorne
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Re: Air direction problems

Postby jthorne » Sun Oct 23, 2011 5:48 pm

Sorted! Followed your advice as I could hear the servos working and found a vacuum pipe pinched badly by another bolt, removed pinch and all works fine!

The a/c is working but is not truly cold. I think it was last recharged in 1999 according to the history, is it possible that it's still on R12? If so is there anyway of topping it up as it seems to work fine in all other ways?

Thanks again for this.

Getting there!!!!!
1977 Daimler Double Six Coupe

almcl
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Re: Air direction problems

Postby almcl » Sun Oct 23, 2011 8:06 pm

If the air con has the original charging ports, then yes, it's likley still on R12.

You may struggle to find someone who has a stock of this and is prepared to use it. But there are drop-in replacements available. See here for one example http://www.subzeroac.co.uk/

You need to have the high and low side pressures measured, once you have established what the refrigerant is. The cause of the lack of cooling can be established just from the gauge indications (there are pages about this in manual.) But likely the system will need to be evacuated, proved to hold vacuum and then have an appropriate amount of fresh refrigerant added.

Conversion to R134a is possible DIY, but getting hold of the refrigerant is difficult and you need the proper mainfolds and gauges and a vacuum pump.

The results of converting to R134a can be quite reasonable, image below is of my 6 cylinder Daimler putting out air below 4°C, although you may read reports of it not working as well.

http://www.jag-lovers.org/include/iv3.p ... rwoQ%3D%3D
Al McL
'93 XJS 4.0 - '05 X type Est 2.0D - '13 XF 2.2D Sportbrake

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jthorne
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Re: Air direction problems

Postby jthorne » Sun Oct 23, 2011 8:24 pm

Thanks I'll get on to them- they're quite close.

Cheers

Jon
1977 Daimler Double Six Coupe

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Montana5
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Re: Air direction problems

Postby Montana5 » Sun Oct 23, 2011 10:09 pm

Please take professional advice when having your system re gassed. R12 Gas has not been made since 1993 and is now illegal, apparantly if it came into contact with a certain everyday household or workshop catalyst, it changed into something very similar to Mustard Gas.

I looked into this a few years ago with my other Car Club whose Cars used the same R12 Gas, however some of this info may have been superceded, of late, by other newer products.
R134A is one of the replacements often used, however they found that apart from being more prone to leakage, R134A didn't always work in some systems due to the need to lubricate the Compressor with Mineral oil, the way the R12 systems did, R134A uses Synthetic Oil, this led to Compressors seizing and a breakdown of seals. R49 and RS24 are similar to R134A, but contain Isobutane and other gasses in minute amounts thus allowing the Mineral Oil to be carried around the system keeping the Compressor lubricated.

Good luck and do let us know how you get on.

Doug.
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