1984-300SD Turbo Diesel
 

I recently searched the archives on the general question question of refrigerants (R12 conversions to R134, etc), and read that when one "cracks open" the system, one should always replace the Rec/Dryer.

My vehicle has not been converted to R134 from R12 ( R12 is no longer available in Canada ). A local AC shop charged the system with R134a, which worked well, but only lasted about a week.

My buddy, a Staionary A.C Techie, pressure tested and revealed a leak at the left elbows of the condensor, which I had replaced, and at that time the shop found leaks at the compressor seals and replaced them.

My buddy then vacuumed and pressure tested the system and found it to be leak-free. He then added R414b 'drop-in' type, but the compressor clutch will not engage, the cause seems to be no pwer going to the compressor from the Rec/Dryer switch (we're still working on that aspect).

:confused: I was wondering if the shop who re-charged with R134 might have fouled the compressor system, or if in replacing the Condensor, we should have also replaced the Rec/Dryer.

Any thoughts, friends?

For the little amount of cash it costs to replace, I do it. They're usually under $50, at times even around $20. You also have the chance to get new oil in the system also as the Accumulator/Drier holds most of it.

Having leaks on a system that's well over 20 years old is normal in my book. O-rings, seals, hoses, etc. do not last forever.

On the compressor not kicking on, that could be due to the different refer in there not having enough pressure but that's unlikely. Hopefully it's simply the pressure switch.

Thanks for the quick response to my A.C Compressor problem.

Btw., here in Ajax, the local MB dealer's price on the Rec/Dryer in Canadian dollars is $213.10, plus 15% in taxes! The Pressure switch is Can$47.30 plus 15% in taxes.

If I can buy an O.E., one from the States for around U.S. $50.00, plus shipping, I'd certainly go that route.

A more specific reason WHY you replace the receiver/dryer has to do with the fact it has a desiccant in it...if the system was open at any point enough moisture has entered it that the desiccant will be worthless...irregardless if the system was evacuated for one hour or for one month....and moisture is a bad thing in the system.

I paid about $14 for my Dryer... it's a Behr if I recall.

134a is not compatible with the desicant used in origonally installed R12 systems.
134a also needs a synthetic oil, eg: POE, as it is not miscable with the oil used in R12 systems.

The expansion valves for 134a freon is set differently too, 134a higher operational pressures will cause over flooding of the Evaporator with a R12 expansion valve.

When concidering a 135a refit be aware that this stuff ruins front seals on most early 506 /508/509 rotory compressors as the 134a will attack the seal.


You will not cool as well on 134 and the extra cost of 12 may be better than trying to use 134.

'

R-12 is banned and illegal to use in Canada, even if one could get it.
I located a shop that said they have R-12a - but I can't find any info on R12a - anyonw heard of it?

Duracool makes a 'drop in' gas called HC12a.
http://www.foxtoolsupply.com/

Uses only 35% of the origonal charge gas .
Has larger molecular size so does not need barrier hoses.

Some places ban this because it is flammable....but there again, so is 20 gallons of gasoline !


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R-12 to R-134a Conversion.
 

I have a bit of experience with this, both doing it the correct way and not. I had a Black 86 Volvo 760 GLE and the compressor locked up. Bought a BN compressor with the new synthetic oil compatible with 134a and a new dryer/accumulator. Worked like a charm. Didn't notice a big efficiency difference in cooling from the R-12. I Converted my 87 300 D without a new dryer. Just vaccumed it down for a several hours and charged it. It's been a year and it still works great. Converted my 93 Gr Marquis this spring without changing the dryer, works just like it did with R-12. Bought my 83 300 SD in the fall knowing the AC didn't work. Didn't realize the compressor was locked up on this on so I converted it too. :rolleyes: OOPs. I pulled the compressor the other day and and I think I will do this one right. :) Yes I do have a a pump and gauges/hoses, they have paid for themselves many times over. In all of them I used 134a with the new oil in it. Yes some of the mineral oil may still be in it. I have read/heard that if you vaccume it down for several hours with no leaks and a good pump that the old mineral oil will boil off. Don't know if it does, but I had a chart with the boiling points of the oils when vaccumed down and I am pretty sure my pump got the system there. It's 7 Cubic Ft/Min pump.

As for the desicant in the dryer, if it gets moist it's toast as far as I know. If it's like the desicant used in electronics packaging you can heat it to 250 Deg F and recharge it. Don't know if this will work or not for an AC, but all you can do is try if funds are scarce.

BTW I live in SE Michigan and my dad has horded some R-12. He has about a dozen 1 lb cans and a 40lb cannister, maybe he would "sell" you some? I can ask.

Last I looked I think the list said this was NOT banned in Canada. Don't quote me on that though.

Researching the NET, I learned that Duracool HC12a is a Canadian made natural product. Being a Hydro-carbon product, it is flammable at some very high temperature; hence the EPA restriction for autos. But it is harmless to the environment, and is approved for use in Canada.

Thanks to all for the responses - I'm learning more every day about A.C systems and refrigerants. :)