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All new A/C, cool but not cold.

B

Ben824

NAXJA Forum User
Location
Woodstock, GA
I have a 1997 XJ 4.0 Auto 4x4 and I recently replaced everything in the A/C system except the compressor. Holds pressure fine, compressor working perfectly and the readings on the gauges are exactly within spec.

But the air in not COLD. It’s cool, but not cold. This Jeep had great A/C back in the day before I messed with it. I had to replace the heater core so I replaced the evaporator while I was I. There because at the time they were both 19 years old and I didn’t want to have to do that terrible task of pulling the dash off ever again. Turns out I would have to, 2 more times. Second time was to replace the cheap aluminum heater core that failed in 8 months. Third time was last weekend when I pulled it off to check the last culprit in a search for a leak in the A/C system. The evaporator failed. Now I have a new evaporator, new lines, new condenser, new drier, and the original compressor. I drained and filled the compressor with fresh oil before reinstalling, even flushing the old fluid out by rotating the compressor pushing the fluid out and repeatedly refilling. I filled the system with 2 cans of R134a. Pressure reading on the gauges are around 40 low side and about 250 high side. Compressor kicks on instantly and runs without any issue. Electric fan kicks on as always and runs perfect.

I’m at a loss for why this thing is cool, but not cold like it used to be. I used to have to turn the thing off periodically because I got too cold even on 90 degree days here in Georgia.

Any help and guidance would be much a appreciated.
 
If the Expansion Valve is either slightly clogged or the wrong one(i.e. wrong orifice sizing), the cooling performance will be poor. The Expansion Valve must perform the refrigerant phase change properly (i.e. liquid-to-gas change in the evaporator coil). IT IS THE refrigerant's phase change that absorbs a very large amount of heat, from the hot air flowing through the evaporator coil, that gives proper cooling. The now hotter refrigerant gas leaves the evaporator coil and then enters the suction-inlet of the compressor. After the refrigerant gas is compressed and then cooled in the condenser (i.e. removal of evaporator heat + heat of compression) it becomes liquid again and re-enters the Expansion Valve to repeat the cycle. Expansion Valves are about $10 (Rock Auto). I'd try that.

Best regards,

CJR
 
The challenging thing with AC is that the pressure readings will be different depending on what the outside temperature is. It is really easy to think you have it dialed in not realizing that it was hotter outside than you expected. At 90 degrees ambient you should be aiming for a Low side pressure of ~50 and a High side pressure of 260. Any chance you still don't have enough gas?



http://rechargeac.com/how-to/ac-system-pressure-chart








Ben824 said:
I have a 1997 XJ 4.0 Auto 4x4 and I recently replaced everything in the A/C system except the compressor. Holds pressure fine, compressor working perfectly and the readings on the gauges are exactly within spec.

But the air in not COLD. It’s cool, but not cold. This Jeep had great A/C back in the day before I messed with it. I had to replace the heater core so I replaced the evaporator while I was I. There because at the time they were both 19 years old and I didn’t want to have to do that terrible task of pulling the dash off ever again. Turns out I would have to, 2 more times. Second time was to replace the cheap aluminum heater core that failed in 8 months. Third time was last weekend when I pulled it off to check the last culprit in a search for a leak in the A/C system. The evaporator failed. Now I have a new evaporator, new lines, new condenser, new drier, and the original compressor. I drained and filled the compressor with fresh oil before reinstalling, even flushing the old fluid out by rotating the compressor pushing the fluid out and repeatedly refilling. I filled the system with 2 cans of R134a. Pressure reading on the gauges are around 40 low side and about 250 high side. Compressor kicks on instantly and runs without any issue. Electric fan kicks on as always and runs perfect.

I’m at a loss for why this thing is cool, but not cold like it used to be. I used to have to turn the thing off periodically because I got too cold even on 90 degree days here in Georgia.

Any help and guidance would be much a appreciated.
Click to expand...
 
Here are my thoughts.

First, what the others said above. Pressures are ambient temp dependent. They are a diagnostic indicator, not a servicing spec.

You also need to measure temps at the center outlet. This temp is also ambient temp dependent.

R134a systems are charged by weight. The R-134a system charge capacity, according to the FSM, is 0.567 kg (1.25 lbs.). You said you put 2 cans in. That sounds overcharged.

Lastly, you said you pulled the dash a few times. Perhaps there's something wrong with the blend door and your not getting full cold.
 
You need to service it correctly. Take it to a shop where they will put it under vacuum for 30 minutes and boil out the water in the system.
 
Alright guys, thank you so much for all the insightful responses! So for those that are not familiar with the 97 system, there isn't an expansion valve. There is an orifice tube. I replaced everything in the system, including the orifice tube, except for the compressor.

I checked the levels on Saturday and the gauges were reading 30 on the Low Side, and about 225-230 on the High Side with and ambient temp of 83 degrees F. Does that seem low to y'all?

As far as how much did I put in, I bought two 12 oz. cans and put in the entire first one, and I left a little bit in the second one but put in most of it.
 
Ben824 said:
Alright guys, thank you so much for all the insightful responses! So for those that are not familiar with the 97 system, there isn't an expansion valve. There is an orifice tube. I replaced everything in the system, including the orifice tube, except for the compressor.

I checked the levels on Saturday and the gauges were reading 30 on the Low Side, and about 225-230 on the High Side with and ambient temp of 83 degrees F. Does that seem low to y'all?

As far as how much did I put in, I bought two 12 oz. cans and put in the entire first one, and I left a little bit in the second one but put in most of it.
Click to expand...

That's a little on the low side, given the temp. The low pressure side should be closer to 40, and the high side closer to 245, give or take a couple psi on each side in the 80-85* ambient temp range.

Were you charging/checking it in direct sunlight? That can throw off the readings.

On an XJ, two full 12oz cans generally does the trick for me, so I would suggest adding in the remainder of that second can to see where it gets you.
 
Did you pull a vacuum on the system before refilling? If not, bingo.
 
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