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Hi All, I have 85 Eldo 4.1 and have AC questions. Car was converted to r134a by dealership. According to my knowledge the only not changed was the condenser. I bought the car and had all AC components replaced with new. Once a year the R4 compressor would fail. The mechanic told me the R4 did not hold up to the heat. The high side 250 to 275 psi. I found a high density condenser and while fitting it also installed a 17 inch 3000 cfm puller six fan to replace the 12 inch. Evacuated system and filled oil and refrigerant. Here is the question. When using r134a charts for low/high side pressure with ambient temperature. When I obtain the correct pressure the cooling efficiency becomes less. The vent temperature lowest 60 degrees. I found online that 30 degrees was acceptable for ambient 90 degrees. I slowly reduced the low side in 5 psi increments to 30 psi at idle high fan, 90 degrees ambient. The vent temp is now 48 degrees at idle. Driving the highway 42 degrees. The compressor stays engaged-no cycling to indicate low refrigerant. It appears to me that it was overfilled using chart. Parameters now are 30 psi low side 175 degrees high side @ 92 degrees ambient. Any thoughts?????
 

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There is no real chart to follow on a car that’s converted. Especially with a different condenser and fan setup from OEM. I recently rebuilt the AC system on a buddy’s Eldorado with all new parts less the condenser. No electronic condenser fan. Charged with 3 lbs 134a, makes 46 degrees center vents on hi fan at idle in park 88 ambient. 35psi low side, 180 high side.

What condenser did you find and what did you have to do to make it fit?
 

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Thanks for responding, Spectra 7-3642. The cross rods support in front of condenser put a couple of washers in front of them. The passenger side top and bottom rubber mounts position did change. The bottom radiator support had hump. I cut 2 slits and hammered down. The top cut about 1/2 inch hole and used sheet metal/body clip and bolt. Passenger side enlarged hole next head light to allow the tubing on condenser to pass. The connection is 8 to 6 so I got Cold Hose to fabricate 3 change over about 20 bucks.
 

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Thanks, it was an '83. If you have the pictures and can post them, please do so. I'm sure someone would appreciate seeing a parallel flow condenser in a 79-85, considering that a lot of the time the 134 and old style condenser doesn't cut it as far as performance.
 

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I have done a little research today and what I found is that GM makes 2 sizes in orifice tubes. .72 and .62. I am curious if they changed the size of orifice when they converted it to r134a. Did it need a change in size? If it had .72 with r12 would .62 create colder air and the need for higher low side pressure (more refrigerant)?
 

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There is no real chart to follow on a car that’s converted. Especially with a different condenser and fan setup from OEM. I recently rebuilt the AC system on a buddy’s Eldorado with all new parts less the condenser. No electronic condenser fan. Charged with 3 lbs 134a, makes 46 degrees center vents on hi fan at idle in park 88 ambient. 35psi low side, 180 high side.

What condenser did you find and what did you have to do to make it fit?
I agree. There is a formula to use to tell you how much R134 to put in to match the R12 weight. Now that you changed the system lineage so who knows how much refrigerant to use. You would probably have to use the same calibration methods used in home A/C systems to find the correct amount.
I suspect the first shop who did the conversion and the R4 failed was due to an over charge which flooded the compressor with liquid refrigerant causing it to fail. A compressor adds heat to the gas from the evaporator. Works about the same as a home A/C system. I'm surprised that it didn't blow a hole in the evaporator coil.

Maybe in hindsight instead of doing this conversion you should have looked at going back to R12. Maybe you didn't know you can buy that off of eBay. I don't think the EPA would be knocking at your door.
 

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I have done a little research today and what I found is that GM makes 2 sizes in orifice tubes. .72 and .62. I am curious if they changed the size of orifice when they converted it to r134a. Did it need a change in size? If it had .72 with r12 would .62 create colder air and the need for higher low side pressure (more refrigerant)?
I used a .67 blue orifice tube-worked great for the purpose. The smaller the orifice, the theoretically better performance you have at low engine/vehicle speed, at the expense of some performance once underway (in my unscientific opinion, smaller is probably better as the potential for the system to expel heat is probably way greater at speed than the restriction the smaller orifice presents) and higher low side pressures Thanks for the pictures, very interesting concept. The core size matched up the same otherwise? Having done it, do you think you could have modded the condenser and not the car to make it work? Maybe cut the lines from the condenser and braze them back together at the size needed?

Like DB2 said, R12 will provide better performance-I converted my car back to it and haven't regretted it a bit. But it makes me wonder what type of performance could be possible with a parallel flow condenser and the R12...
 

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Hi All, I have 85 Eldo 4.1 and have AC questions. Car was converted to r134a by dealership. According to my knowledge the only not changed was the condenser. I bought the car and had all AC components replaced with new. Once a year the R4 compressor would fail. The mechanic told me the R4 did not hold up to the heat. The high side 250 to 275 psi. I found a high density condenser and while fitting it also installed a 17 inch 3000 cfm puller six fan to replace the 12 inch. Evacuated system and filled oil and refrigerant. Here is the question. When using r134a charts for low/high side pressure with ambient temperature. When I obtain the correct pressure the cooling efficiency becomes less. The vent temperature lowest 60 degrees. I found online that 30 degrees was acceptable for ambient 90 degrees. I slowly reduced the low side in 5 psi increments to 30 psi at idle high fan, 90 degrees ambient. The vent temp is now 48 degrees at idle. Driving the highway 42 degrees. The compressor stays engaged-no cycling to indicate low refrigerant. It appears to me that it was overfilled using chart. Parameters now are 30 psi low side 175 degrees high side @ 92 degrees ambient. Any thoughts?????
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The vent temp is now 48 degrees at idle. Driving the highway 42 degrees.
The compressor stays engaged-no cycling to indicate low refrigerant.
It appears to me that it was overfilled using chart.
Parameters now are 30 psi low side 175 degrees high side @ 92 degrees ambient.
Any thoughts?????

YES -
one word immediately comes to mind - PERFECT!
 

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Discussion Starter #14
Hi guys great comments. I bought the car with everything converted. That R4 was on its last leg, lasted about a week. Took it into the shop and as recording replaced hoses and evaporator and orifice and compressor and flushed tube type condenser. I have had newer cars and trucks with r134a with no problems. My understanding the hoses are special, I learned this with consulting with Classic Air for my 67 Eldo, the r134a with sweat through rubber compound on older type, not sure if it applies to 85 hoses. Drove it for a year ice cold and they replaced it for free. Having made the initial investment, I did not want to spend more money to convert it back. The parallel condenser cost less. If the 250 to 275 psi high side was causing the failure. The remedy to me was to reduce the pressure, which it has done by nearly 100 psi. I have driven it for a year no problems but this year is a little hotter and the blower motor finally gave out. I replaced the motor. I keep thermometer in center vent. The reading was a little different. I read where increased air flow indirectly affects pressure. I hook up some gauges and low side was 35 psi high side 175 at 80 degrees. I filled her to 45 psi low side 200 high side at 80 degree. Drove around steady 60 coming out vent regardless town or highway. Which was hotter than before. Like I mentioned before I read 30 degrees at 90 low side is ok so I did it and it runs much cooler. The compressor does not cycle. The minor mods to radiator support and upper support and enlarging the hole that was already there is what I was comfortable in doing. I can solder copper plumbing but have no experience in brazing semi high pressure fitting. I asked a guy locally who does fitting and he wanted 600 to make the 3 inch fitting I got from Cold Hose for 20. I think he quoted this price because he did not want to mess with it. I thinking the smaller orifice next year when I service it. The pressure will be higher behind the orifice and with it expands across the orifice should be colder. This will cause a slight increase highside, but I also think since they are connected the low side will increase also. Example I put more refrigerant in low side pressure goes up and high side also goes up.
 

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Discussion Starter #15
Hi Guys new topic, outside temp indicator on the Ac control sometimes reads accurate and sometimes reads 8 degrees less than outside. Is the this ambient temp sensor?
 

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Discussion Starter #17
Thanks, let me pick your brain a little. I have noticed the compressor never kicks off(except on Economy or off position) I run it from 60 to 90-High and Low fan settings. Is this normal? I have another concern with reducing the low side when over filled that may be some Pag 150 oil might have come out also. I think R4 compressors are little noisy. I was think of adding 3 oz.
 

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If you are in the AUTO position, the A/C compressor will run all the time until it gets down to about 35° ambient temperature. Perfectly normal and as designed.
It also runs in the DEFROST mode at ANY ambient temperature.

I have another concern with reducing the low side when over filled that may be some Pag 150 oil might have come out also.
If by "reducing", you mean bleeding down the pressure from the service port, you won't loose any oil. That would take a catastrophic release as in an accident. Just release it slowly.

Disclaimer:
Before I get corrected, "technically", it is illegal to vent to atmosphere, but I won 't tell.
 

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Releasing to atmosphere is regulated by state. Some will prohibit it period. Others will limit HVAC work to pros which are required to have reclamation machines. Finally, some states will allow consumers to work on their own vehicle (ie TX).
 
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