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740 Service R12 or convert to R134-a

When my system was low on 134 it constantly cycled the compressor. It only actually ran it for a second. Then it would shut off and immediately start up again. I checked the pressure on the low side and it was perfect but no cooling. Only has a low side port on 93 240. So I took it to the shop. They pulled out the 134 that was in there and weighed it and it was only half the amount it was supposed to have. Filled it for me and it's been great since then. They said they couldn't find a leak.
 
KeizerBrickGuy said:
Its in behind the passenger footwell, below the glove box.
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PromiseRing said:
Wait, I bought an orifice tube, not an expansion valve. I really don’t know **** about ac systems (obviously).
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KeizerBrickGuy said:
The R12 systems in these cars utilized the expa soon valve design as it was more effective at metering the refrigerant.
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First line of first post: "1990 740 LH2.4"

Unless I, and all the parts stores, are wrong...
740s didn't get expansion valves.
240s did.
 
Yeah low on refrigerant can cause too much cycling of the compressor. Always on....not quite sure what the answer is from over here. I use a machine that precisely weighs the Freon. I have slightly overcharged before (by .2 or .3lb) and high side pressures shot thru the roof really quickly and cut the compressor. Over and over again.

740 has an orifice. It's in the tube that runs along the passenger frame rail.

240 has a TXV.
 
I forget exactly where it is. Actually, I've never done one. Ha.
I recall a 740 owner that found a previous owner had installed two orifice tubes!

Unplug your compressor and see if it still is stuck on mechanically. Too high or too low of a charge will cause it to cycle too fast.
 
ZVOLV said:
I forget exactly where it is. Actually, I've never done one. Ha.
I recall a 740 owner that found a previous owner had installed two orifice tubes!

Unplug your compressor and see if it still is stuck on mechanically. Too high or too low of a charge will cause it to cycle too fast.
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It only comes on when the snowflake setting is selected. It used to cycle on/off really fast before I evacuated the system and recharged. I was low then I would assume. Even when I manually jumped the compressor, condenser would stay cool and ac wouldn?t get hot. But I?ve since fixed that.
 
ZVOLV said:
740 has an orifice. It's in the tube that runs along the passenger frame rail.
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PromiseRing said:
Didn?t see anything on the frame rail, I looked. I saw the google pic too that shows where it *should* be, but isn?t.
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ZVOLV said:
I forget exactly where it is. Actually, I've never done one.
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According to page 7 and later...
https://people.ohio.edu/ridgely/Volvo_docs/Volvo%20740-AC_r12-r134a%20retrofit.pdf

On model years 1991 and earlier (780 -1990) the orifice is located in the receiver inlet at the firewall.

On model year 1992 and later (780 1991-) the orifice is sited in the High-Pressure pipe at the pipe joint on the side member
 
Sweet. Sucks that I already vacuumed and charged the system but didn’t replace that tube. Could contaminates in that tube be causing the poor quality at idle or is it likely a charge issue?
 
When a compressor fails the particles end up stuck in the orifice tube. Sure it can cause poor cooling when it's clogged.

Without guages and a known exact charge there is no way to check what's going on.

With guages, if the high side pressure isblow and then you rev it up and it goes to normal it's probably a worn compressor.
 
ZVOLV said:
When a compressor fails the particles end up stuck in the orifice tube. Sure it can cause poor cooling when it's clogged.

Without guages and a known exact charge there is no way to check what's going on.

With guages, if the high side pressure isblow and then you rev it up and it goes to normal it's probably a worn compressor.
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No high side fitting on these cars.. it?s a ****ing guessing game I guess. I vacuumed the system for like 15 minutes so surely I got almost all of the old r134 out, then installed exactly 12oz of ES12A.

I can get a low side reading sooner or later:roll:
 
I've seen where shops cut the high pressure hose and add a coupler that has a test port in it. If you really had to read high side pressure it is a choice to make. I guess the other approach is to add a fitting at one of the connections like how that oil cooler was added in the oil cooler for police model 240 thread. They inserted a fitting right where the automatic trans oil lines connect at the radiator.
 
Ah I must have messed something up when installing the receiver drier. Her ac stopped working and there was some green slimy crap under the receiver drier fitting (big one). So aside from the green orings on the small stuff, anyone know which seals are supposed to go on the 2 massive fittings on the receiver drier? Are they the green orings or the thicker black seals?
 
bump. Would love to get this going again.

So theres 2 large fittings on the receiver drier. Do they get your typical green oring only, or do they get a green o ring + another larger black seal? I cannot remember when I removed it. Worst case, I'll pull apart a JY car and take a look, or try to find a schematic.
 
PromiseRing said:
Why does that matter? R134 with r12 orings can be an issue but I think any seals are fine with es12a. I just remember seeing a larger black seal where the lines come into the receiver drier but I could be wrong.
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It doesn't matter. The green seals are fine with R-12 or ES12. The original Volvo seals in an R-12 system were blue. Not that it matters. It just means if you encountered a different color, the seal has been replaced.
 
2manyturbos said:
It doesn't matter. The green seals are fine with R-12 or ES12. The original Volvo seals in an R-12 system were blue. Not that it matters. It just means if you encountered a different color, the seal has been replaced.
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Thanks, I figured just as much. Do you know if there?s any seals aside from green (or blue if OE) that go into the large inlet and outlet of the drier? Or just the green/blue ones.
 
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