Late model / R134a A/C for 240s - what components were changed from R12?

Major Ledfoot · 2020-09-14T04:48:06+00:00

Major Ledfoot Following on from @carnut222's yellow 245 build, it was mentioned in the thread how that latter--day 240 air conditioning systems were more eff...

TL_V70

High side is high pressure hot gas up to 300psi in some climates. Low side is low pressure cold refrigerant around 5-20 psi. If u ever get the chance to look at aircon guages you will see a -degc temperature on the low side guage this is roughly what the temp of the refridgerant leaving the evaporator is so that's why u need to measure the low side temp with the capillary switch to stop the evaporator freezing over as it should switch to compressor off to cycle at a pre determined temp eg 1 degc as u set it to

TL_V70

I broke these old ones they should be a 0 psi but you can clearly see refridge temp to psi on the blue low side

jamesinc

Low side is what I meant ?

TL_V70

? and now we are all air con gurus lol. Just some info no harm ment ?

Major Ledfoot

TL_V70
? and now we are all air con gurus lol. Just some info no harm ment ?

lol, I know I am a very long way from being a guru on these things...

@TL_V70 would you agree that a parallel flow condenser is more effective than a tube & fin unit of the same approximate size, presuming the evaporator is the same?

And what are your thoughts about R1234yz, apart from it being expensive?

TL_V70

Depends what world your equipment is in eg car truck mining. Parallel is good in the automotive world qnd yes more efficient. All condensers require good cooling eg a fan or good constant air flow is the key. Personally from my experience in mining I quite like tube and fin design its less deceptable to dust dirt and mud clogging up and normally a more robust design both have pros and cons. Automotive is a different. parallel is in most cars these days. Honestly R1234yz is to new for me i know about it but never had anything to do with it my industry tends to be behind the times only new cars potentially come with it. Yes it will replace R134a eventually but not for along time. 10+ yr period, same sernario when R12 was slowly fazed out. The whole world has to change so not a fast activity.

DW42

For fitting air conditioning to a 140 series or any old volvo that never had it, is it simpler and more reliable to go with an electric system like this (it's from the UK, but there must be places here that retrofit electric air con) https://www.classicretrofit.com/collections/electric-air-conditioning?page=1.

The air con on my 1990 240 has been a PITA over the years due to various leaks and failures.

buddyglitch

jamesinc sorry to revamp an old one James. Just wondering if you remember which TX valve you acquired from Rockauto? In the midst of reviving my A/C on a 1990 wagon, retrofitting R134a.

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jamesinc

@buddyglitch uhhhhhhh I don't recall, but Four Seasons is what I would normally pick. You can check/adjust the valve if necessary. The R12 valves are set 3.5 turns back from bottomed-out, and the R134a valves are 7 turns back. To adjust the valve it's just an Allen key but you have to insert it through the valve outlet (which unfortunately means you can't adjust it without degassing/opening up the system).

If you're reviving an old system there are other things you might want to do too, if so consider starting a new thread for it

buddyglitch

Awesome tip, thanks mate. Degassed the system a couple years ago when doing an engine swap. Installing some new o-rings, a drier and modifying my E-fan to cycle with the clutch. will see how it goes! Will start a thread if I have further issues. 👍

jamesinc

buddyglitch sounds like you have it well under control. If you can get hold of some, Nylog Blue on the o-rings, people umm-and-ahh about wehther it's necessary, but I used to occasionally find myself fighting slow o-ring leaks, and since using it, not one issue!

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