Can An AC Condenser really Be That Bad?

[tempest411]

Hello,


Since I got my '88 running a few weeks ago I've been trying to 'show it some love' by fixing a few other things on it. 10-11 years ago I got the AC working and went with R134a in a system with a new compressor, expansion valve, drier, condenser, and hoses refitted with the barrier-style material. It never worked well. I did vacuum down the system to both check for leaks and get rid of any moisture. Fast forward to the present day and I find the AC doesn't work. Enough refrigerant leaked out from valve cores that worked their way loose that it wouldn't kick on, so I decided to throw more parts at it. I replaced the compressor, which had been leaking (and always 'growled') as evidenced by the oil coming out of it, the drier, and the expansion valve. I pumped it down and let it sit for several days; it lost perhaps 1" in three days! This time I back filled it with R152. I was surprised to see just one 10oz can of the stuff brought the static pressure to 80psi. I had high hopes based on what I read about it's cooling capacity being similar to R12, but after filling it with nearly 20oz of the duster gas the pressures are quite high and the performance is disappointing. I have 70psi on the low, 275psi on the high side, and vent temps that are BARELY cooler than ambiant (low/mid 90s). Feeling the lines that go into the expansion valve, the exhaust side is just cool, but not cold to the touch, and the inlet line is HOT! I thought that was odd as it shouldn't be THAT warm after going through the condenser. As an experiment I sprayed water from a hose on to the condenser and the performance improved drastically. It also works better while driving around, which is to be expected...but the performance was still nothing compared to what I got hosing it down with water. I did flush everything with proper AC system flushing solvent and compressed air through one of those flush-gun gadgets. the evaporator and condenser are clear. I used ester oil for the lubricant. Will fitting a newer style parallel flow condenser improve things much here? Can anything else by amiss?



Thank you for your advice!

 

[Agreen]

More refrigerant doesn't equal more cooling. The r152a is a different gas than r12 and r134a, although the pressure/temperature tables are very similar to R12. You need about 60% of the weight of what it originally calls for. Try "dusting your keyboard" with some of that refrigerant in your system and see how much it improves.

 

[Agreen]

I did a write-up on this a while back. Give it a look:
https://www.s10forum.com/threads/how-to-r152a-conversion.493953/

 

[tempest411]

I did a write-up on this a while back. Give it a look:
https://www.s10forum.com/threads/how-to-r152a-conversion.493953/

Small world! I was already aware of your post in my previous research on this. At present, if I had ZERO leakage in the charging process, I have 55% of the R12 capacity in the system. I know had some leakage as those can-tap things don't seem to seal 100%, so I could stand to add more. But because of the higher than expected pressures on both the low and high sides, coupled with the poor cooling performance, my 'spidey-senses' are telling me my condenser is inadequate for the job. I found a parallel flow unit that looks to be a drop-in on my Renix era rig for $60.00, so I ordered it. Now I have to get a 50' hose to go from my Jeep to inside the house to blow off all the keyboards and other gadgets...

 

[8Mud]

Just some possibilities not a difinetive answer, but at first blush your numbers indicate you have some air mixed in with your freon. One thing many people neglect is purging the charging lines. The quick way is to squirt a little freon thorugh the lines before connecting. It doesn't take much air in the system to drive your pressures way up.

Condensors on the XJ are hard to clean. I've found stuff stuck between the condensor and the radiator even after high pressure cleaning. I take the top radiator mount off, loosen the top condenser mount and gently sperate the condenser from the radiator just enough to get some compressed air and/or a long handled bottle brush in there. A quicker way to check is to take the grill off and shine a high power flashlight backwrds through the radiator/condenser sandwich and see what you can see. Does your aux fan come on when the compressor clutch is engaged? When you clean the condenser be carefull not to flatten the fins. If you do flatten some buy yourself a fin comb, they are cheap. Condenser cleaners don't touch feathers, fibers, some kinds of dirt and other insolvubles .

 

[tempest411]

Just some possibilities not a difinetive answer, but at first blush your numbers indicate you have some air mixed in with your freon. One thing many people neglect is purging the charging lines. The quick way is to squirt a little freon thorugh the lines before connecting. It doesn't take much air in the system to drive your pressures way up.

Condensors on the XJ are hard to clean. I've found stuff stuck between the condensor and the radiator even after high pressure cleaning. I take the top radiator mount off, loosen the top condenser mount and gently sperate the condenser from the radiator just enough to get some compressed air and/or a long handled bottle brush in there. A quicker way to check is to take the grill off and shine a high power flashlight backwrds through the radiator/condenser sandwich and see what you can see. Does your aux fan come on when the compressor clutch is engaged? When you clean the condenser be carefull not to flatten the fins. If you do flatten some buy yourself a fin comb, they are cheap. Condenser cleaners don't touch feathers, fibers, some kinds of dirt and other insolvubles .

I did purge the line each time I connected a can of refrigerant to the center port of my gauge set. Do you by chance have one of those IR temperature guns? Maybe if you think of it, can you take a reading on the liquid line where it enters the expansion valve when your AC is on? It'll be a few weeks before I can mess with mine again. The radiator fan diode went south and trashed the wiring that goes from the AC relay to the radiator fan relay. But when I get it going again I'd be interested in comparing temps.

 

[8Mud]

My 88 is in XJ heaven so no temps.

You have to purge the line into your manifold and the lines out of your manifold, anyplace that can trap air.

It is also better to vacuum the system through the manifold, then connect your can, then slightly loosen the connection at your manifold and let it squirt a little. Just a thought if you try to connect or disconnect to your compressor ports when the system is in vacuum you may suck some air, it is always a possibilty the seal may not be perfect. Vacuum is always the prefered way to minimize air, a purge is second best.

I'm just trying to think of anything that can go wrong, it gets kind of confusing sometimes with multiple valves.

What kind of vacuum pump did you use? Some are better tha others, some need oil to work well. If the oil resevoir goes dry it may not vacuum well.

Just some thoughts.

 

[8Mud]

I did purge the line each time I connected a can of refrigerant to the center port of my gauge set. Do you by chance have one of those IR temperature guns? Maybe if you think of it, can you take a reading on the liquid line where it enters the expansion valve when your AC is on? It'll be a few weeks before I can mess with mine again. The radiator fan diode went south and trashed the wiring that goes from the AC relay to the radiator fan relay. But when I get it going again I'd be interested in comparing temps.

I did refrigeration for so many years all I needed was a finger tip If the high line blisters your finger tip it is to hot. Hot enough so you can hold your finger tip on there for 2-3 seconds is fairly normal. Until the system (condenser) gets down to temperature the high side and low side temps/pressures are an unreliable indicator. They change pretty much continously until the system stabilizes.

 

[8Mud]

IMO you really need that aux fan to be working. I'd set mine up in the shade at a little higher than normal idle, with the doors open.

 

[tempest411]

What kind of vacuum pump did you use? Some are better tha others, some need oil to work well. If the oil resevoir goes dry it may not vacuum well.

Just some thoughts.

IMO you really need that aux fan to be working. I'd set mine up in the shade at a little higher than normal idle, with the doors open.

The vacuum pump I'm using is complete overkill for the job. It's an Alcatel roughing pump more commonly used to back turbo molecular pumps on high vacuum systems. I got it from a testing lab that was using it on an RGA. They did ground water testing for a bunch of companies in the S.F.Bay Area. It weighs about 80 pounds and draws the whole system down below scale in a matter of seconds. My electric fan was working while I was operating the AC a couple days ago. I now think the lack of flyback voltage protection on the new compressor took out the diode in the radiator fan circuit. The radiator fan diode broke down and became a conductor...Current from the yellow lead from the ignition switch went to ground through the orange wire from the AC relay...I'll have it repair within a few weeks. I have to source new terminals for the relay holder and dig into the harness that goes in front of the radiator between it and the grill. That orange wire is cooked!

 

[Agreen]

He's right about the aux fan. It HAS to work to get the right amount of airflow across the condenser at idle. You could just temporarily wire a toggle switch to it if necessary.

And the purging part IS very critical. I found that a lot of people misunderstand how long it has to purge. When you unhook the yellow hose from the vacuum pump and put it on the can tap, you suck air in. Once the can is tapped, crack the yellow hose fitting at the manifold and leave it loose until it starts to ice over. It's not as much refrigerant as you think it is. Once it starts coming out liquidy and icy, then you can (carefully... maybe wear some gloves or something) tighten the hose back up. NOW you're purged and ready to charge. I like to charge juuuust enough to get it cooling. You want to hear the compressor cycling. About 30 psi on the low side is what you're looking for. Sometimes a little higher. A rule of thumb I follow for pressures (as do 90% of mechanics) is that the low pressure should be the same number as the temperature of the evaporator core. Not dash vent temp, evaporator temp. The high pressure side should be ambient temperature plus 100, and add a little for humidity. It's very ballpark, but of you get it close enough using that you'll be very happy. You'll find that you will use way less r152a than you expect.

 

[tempest411]

Eh, I found out that my electric fan was NOT coming on with the AC, but only by the temperature of the engine. More than ten years ago when I changed over from a closed to an open cooling system I switched from a two-prong fan switch on the hot leg of the radiator fan relay to a single terminal grounding type sender on the ground leg of the fan relay. The main reason for this was that it allowed me mount it in a later thermostat housing on the cylinder head, and I was able to get it in a lower temperature than stock. I always felt the factory sender turns on the fan at too high a temperature, and with this modification my Jeep definitely ran cooler. It stays 'left of center' on the gauge, whereas before it often ran up to 210F on hot days. Hotter still if I was going up a lot of hills. However, without realizing it at the time, when I moved the relay trigger to the ground side I defeated the AC switch-on over-ride function. That explains why it always seemed to take a while for the AC to start working in the past! But I'm correcting this now...I found that an extra 180F fan switch from another project, an '87 Porsche 924, fits right in to the radiator I installed last fall. This radiator has both a radiator cap neck for the later Jeeps with the open style cooling systems, AND the threaded port for the fan switch used on the Renix models, like mine. The original radiator I installed when I did the conversion did not have this extra feature.



Right now I'm looking at a lot more work than I bargained for, thanks to a short circuit that happened the other night. I've pulled the radiator out tonight. Tomorrow, or later today I'll pull the harness that goes from the driver's side to the passenger side in front of the radiator out and repair the wire(s) that were damaged. Later as parts arrive, I'm also going to install a new parallel flow condenser, and also re-wire the radiator fan relay back to factory spec, including the diodes that self-destructed on me and caused the short circuit. I'll also add a diode to the compressor clutch for the flyback spike that likely took out the other diodes...