74se
Settling In
Posts: 118
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Post by 74se on Jul 11, 2021 18:08:54 GMT -5
My 1974 Charger with a 318 auto with (non functional) factory a/c. I want to get it going again. Their was a weak charge in it when I bought the car several years ago. The clutch on the compressor no longer engages, but when I jump the low pressure switch it will engage. The dash switches work,but the blower seams a little weak. I want to try to convert it to 134a. So my question is what do I need to do to make this happen? What options are out there?
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DynoDave
CO-ADMINISTRATOR
Motown Mopar-Wizard
Posts: 11,160
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Post by DynoDave on Jul 11, 2021 21:30:48 GMT -5
My 2 cents... The proper, full conversion to R134A requires some work. There are fittings that cut into and permanently install over the factory R12 fittings (once done, there's no going back without replacing the components those fittings are on). Any seal or O-ring should be replaced for one that is R134A compatible. The system should be cleaned to remove all of the old refrigerant oil (mineral), and a new R134A compatible refrigerant oil (PAG) installed along with the R134A. Then there are the rubber lines. The R134A molecule is smaller than the R12 molecule. That's why all the O-rings and seals need to be changed. They cannot contain the smaller molecule for long. The same is true of the rubber lines. The real fix is to replace them with newer lines designed for R134A. Lastly, R134A is less efficient than R12, so there will be some minor loss of temp as measured at the vent. Coming from a non-working system, if you don't have anything to compare it to, or a way to do a back-to-back comparison, you may not notice. If I sound like I'm not much of a fan of this conversion, that's true. I'm not. R134a works at different pressures. If you have a thermal expansion valve or orifice tube, are those calibrated for the proper refrigerant? Is your pressure cutoff switch properly calibrated for this refrigerant? Factory systems were designed with this less efficient refrigerant in mind, and the condenser and evaporator are sized accordingly. Not much you can do to change that in a retrofit. In the initial panic that followed the introduction of R134A, when everyone thought R12 would be unobtainable in just a few years, these retrofit jobs were very popular. But the fact is that today you can still get R12, or R12 replacements. Personally, I don't see the need to go there. The last R12 system I had in a daily driver was an '86 Omni in the early 2000s. It had a slow leak I was not going to spend the money to fix, so I used a product called DuraCool, a drop-in R12 replacement. Twice as efficient as R12, you used half as much. I had very good luck with it. Full disclosure, DuraCool is a hydro-carbon based refrigerant, and thus flammable. The "new" refrigerant today that replaced R134A (R1234YF) is also mildly flammable. Personally I have no heartburn over this, but some folks do, so I thought I'd mention it. R12 isn't flammable per se, but it does make phosgene gas as it "burns", which was known in WW1 as mustard gas. So none of this stuff is particularly friendly in a fire. (Trivia: There used to be an R12 tool for leak diagnosis that used an open flame. When the flame changed color, you had found your leak. Just be sure you don't inhale the fumes!) DuraCool LinkNow, the economics of this may not be as bad as they seem. Because lets be honest...the newest of these 3d gen systems is now 47 years old. How "good" can ANY rubber part (O-ring, seal or hose) really be? So to do the job properly, you are probably looking at the expense of replacing all of those perishable rubber parts anyway. And the only replacements sold are 99% likely to be R134A compatible (and R12 too). So you likely will face some of this expense either way. Sorry, probably way more info and opinion than you were looking for...
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Post by commodore on Jul 12, 2021 3:24:50 GMT -5
I can tell you from my experience with a 73' 318 Charger.
Since where i live r12 is not available anymore,i asked "originalair.com" what to do. They told told me to remove the regulator valve on the back of the compressor and install their cycling switch/relay. then i ordered the cut in fittings for r134a and installed it. while im at it,i replaced the expansion valve and dryer and all o-rings,also i had to replace the condenser due to a broken line.
i whent then to my mechanic and let him evacuate the system and refill it with r134a.( it takes a huge amount of gas..about 1,3Kg.) it turned out,after refill,the pressure switch wasn't working. so i ordered one and we have to evacuate the system once again and since then (about a year) the system works fine and blows cold.
i must say,i dont expected it to be that simple. it has the original cooling lines from 73' and the compressor and clutch still worked good.
But the Compressor is very noisy..:-)
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Post by Nacho-RT74 on Jul 12, 2021 4:05:12 GMT -5
My 1974 Charger with a 318 auto with (non functional) factory a/c. I want to get it going again. Their was a weak charge in it when I bought the car several years ago. The clutch on the compressor no longer engages, but when I jump the low pressure switch it will engage. that's obviouslly the lack of gas ( or no gas ) on the system and the purpouse for the low pressure switch. A compresor working with low or no gas will get compressed air, and this captures humidity, so water flowing through and getting rust all around into the system The dash switches work,but the blower seams a little weak. The blower is a HUGE current sucker. With engine off and all the contacts along the system makes the blower to get low current it makes a poor power flow up to the blower. It's tipical to find the blower switch plug melted due overheat. The blower switch gets so hot able to burn yout finger at the switch lever touch. Points inside the blowe switch is the WEAKER point of all. I saved this using a 6 relay setup, one for evary speed that I can explain you later if wished. You won't need to cut a wire, but will need to make a harness for it and inser it into the A/C harness. Not hard to do. I want to try to convert it to 134a. So my question is what do I need to do to make this happen? What options are out there? pics attached. I think missed one page ( last one ), unfortunatelly the magzine is in Vzla and I'm in Spain, but these pages pretty much sums all. Rockauto got the Expansion Valve and Filter ready for R134 ( 4 seasons brand ). No need to rebuilt or readjust the ones you have. I can grab to you the PNs. They sell both, for R12 and R134. They share allmost the same PN, but one digit diff to state that diff
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Post by Nacho-RT74 on Jul 12, 2021 4:11:25 GMT -5
I think the pics came out small to be able to read them... here the album link and you will be able to zoom them in postimg.cc/gallery/ChwjbjBand this is one of the emails I got from Rockauto crew LOOOONG time ago ( back in 2010 )... take a note on the difference for PNs Hello,
I did not find part number 38844 listed for a 1974 Charger, and would not advise trying this, since it's not listed for your vehicle.
Four Seasons has given part # 33280 for vehicles with Dealer installed air, and part # 33259 for vehicles with Factory installed air.
The technician at the manufacturer said that all of their parts starting in 33 will be R134a compliant. If the parts starts in 34 it will only be compatible with R12.
Thank you,
Jeff RockAuto Customer ServiceI was asking about their Expansion valve PN listed as 38844 on their website and the R134 compatibility, and also requesting about the filter 33259 ... but then I got that answer. That made me to get the right parts ready for R134. The 33 and 32 PN diff applies to the Expansion valve too, just that I requested by the wrong Expansion valve. Then I got corrected and got the right one. They came with the correct green O rings for R134
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74se
Settling In
Posts: 118
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Post by 74se on Jul 12, 2021 18:02:14 GMT -5
Thanks for all this advice. I have some options now.
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Post by 71se3834v on Jul 12, 2021 21:16:57 GMT -5
I don't remember the fittings cutting into the old. Seem to remember just threading them on. When I did mine per the advice of someone who knew alot more than me I did the following: The system was closed but no freon present. Removed the sump on the compressor, cleaned out old oil, new gasket and shaft seal (twice cause I installed the first one backwards. Had new lines built. Reverse flushed evaporator and condenser. Bought new dryer, pressure switch and expansion value. New line seals and gaskets at the compressor. Removed the valve on the back of the compressor (can't remember the name of it at the moment). Installed new Ester oil per the factory manual. Pulled a vacuum and install R134a.
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Post by Nacho-RT74 on Jul 13, 2021 3:17:20 GMT -5
EPR valve is the name for the one on back of compressor.
About the Expansion valve PN I was requesting, dunno why that PN was listed for 74 but I know I finally got the correct one from them meeting the 33xxxx PN for R134 refrigerant gas. I think checked the 73 model year list and found it ( is the same for all 71/74 ). Is not uncommon some mistakes like that. On engine mounts rockauto had listed for 73 still the pre 72 setup not the spool mount. 74 model year gets the right one thought! Dunno if they already corrected that.
I must say the 4seasons dryer/filter is allmost exact same piece than the stock one. Just some minor differences on the visor/lense which on the stock one is serviceable ( I guess for the O ring ) but on the replacement no. Expansion valve is exactly the same piece.
On my car, when I made the conversion kept the stock seasoned hoses and serviced the dryer with the right desicant. Also kept stock expansion valve ( I still didn't have the new replacements in hands ) I even kept the EPR valve in place!, but at certain point it began to leak I gues through the old hoses pourousity ( sp?), so when servicing the A/C system again decided to replace the hoses for R134 ( reusing the fittings ) and removed the EPR valve. In any case I did fit the thermostatic switch for the clutch on/off cycle and still haven't. My A/C system worked fine in both stages. Just quite often I got ICE ( yes a white block of ICE ) around the back of compressor outlet when the EPR was still in there, LOL.
I found later the thermostatic switch was used on A bodies by MaMopar, while the EPR valve was used on B, C and E bodies C bodies getting a more complex A/C system too. Thermostatic switch gets the sensor mounted into the evaporator "grill" on A bodies stock setup, not at the expansion valve like shops use to mount when adapting.
I still haven't mounted the new 4 seasons parts on my car, since I sent my car for a DEEP body job back in 2013 and still is not assembled ( yeah... right... this has been a joke from the body shop all these years ), but when the assembly time comes, will be installing also a new aluminium condenser ( exactly to the stock iron piece ), the new 4 season parts and the thermostatic switch just like A bodies did into the evaporator "grill".
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Post by Nacho-RT74 on Jul 13, 2021 5:49:53 GMT -5
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Post by Charlie on Aug 30, 2023 11:37:49 GMT -5
If your system is still set up for R12, I would just pay more for the R12 and be happier in the long run. Up until recently, you could still get R12 on ebay. If you look often, some still slips thru the cracks. Make sure NOT to mistake the R12a for R12. Not the same... although it will work. I think that is propane if I'm not mistaken. You'll see R12a all over ebay. I recently acquired a nice handfull of cans over the past few months. My average price per can was about 30 dollars. Since the 'bay stopped allowing the sale of R12 this year, another site sells it now... www.mercari.com/search/?keyword=r12%20 ... and it seems be be quite a bit pricier. Looks like 3 cans for 200 to 250 dollars is common. This increase could be simply due to summer demand. But if it was me and my car had never been converted to 134,, and I still had a slight charge in there from years ago, I'd certainly go ahead and give it a try. But, I bet it's likely you need to change some hoses, and it wouldn't hurt to change the drier. You might also discover that your front seal on the compressor is leaking. Does it look greasy around the front of the compressor? Is there old grease marks under the hood just above the compressor? No matter what you put in there, it might leak out. However, the R12 will have greater staying power in the system than 134. If the site you purchase from requires you to have a 608 certification (and most will), you'll need to get that. Cost about 25 dollars... here's one here... ww2.epatest.com/epa-section-608/openbook/ and there are several others. I did mine in an hour. I am a hard core believer that R12 systems should have the correct refrigerant in them. My Charger has 134a in it and it really does not do squat. Temp at the vents will get to 60 degrees. I am preparing the go back with R12. My 77 F150 had a nice conversion with a new Sanden compressor... and it works. It is generally pretty cold as long as the temp is 92 or below outside. Above 92, it struggles. I am considering changing it back to R12 now that I have some. QUESTION FOR A/C GURUS... Lately I have been looking for info on the oil. It's well known that you must clean out the oil R12 oil when converting to 134a. How about going the other way? If my systems currently have the PAG oils in there, can I go back R12 without changing back to mineral oil?
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