"Max A/C"

[mwilk012]

Nun-ya
If you think R1234yf performs well, you haven't seen a really good R12 system work. R1234yf along with R134a both suck. Neither hold a candle to R12 systems in terms of cooling capability. R12 systems could easily cool down a vehicle very quickly and make frost on the vents, if you ran them on max. These days, your vehicle is just getting reasonably comfortable by the time you arrive at your destination when running short errands around town. Marginal is what R1234yf and R134a systems are, and they make us like it.

Furthermore, at least one study concluded that R1234yf was about 14% less cooling capacity than R134a. R1234yf vs R134a in automotive air conditioning system: A comparison of the performance - IOPscience

Evaporator temps below freezing are a defect, not a feature.

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[Daytriper]

I noted that my AC isn't keeping up with cooling when the temperature is in the 90s or above. I attributed this to my quick and dirty recharge after installing a new engine before a trip. While driving up the San Juaquin valley in upper 90s and above it was not quite cool and relaxing, with the AC blower on the highest setting and the recirculation button lit.

So, today, I thought I'd check the manual for anything I'm missing. It shows that there is a "Max A/C" button on the Uconnect that supposedly does something. I started my JLUR in the driveway and while idling, I couldn't tell the difference between this button on or off. Anyone use this?

Try some roof panels, not only quite things down, but they have insulation qualities also, warm, and cool.

 

[J.Ferreira]

I believe it normally changes to upper dash vents (face?), fan at full, temp at coldest and turns on recirculation.

Yes, like every other car with a max AC function.

 

[roaniecowpony]

Try some roof panels, not only quite things down, but they have insulation qualities also, warm, and cool.

I'll get to that. But, I'm going to re-charge the system again and make sure I pull a good vacuum using my micron gauge, and let it pull down with the pump on for at least an hour. I also need to change the oil in my Robinair SPX 4 cfm 2 stage pump. It's been a long time.

 

[Jeffy56]

I'll get to that. But, I'm going to re-charge the system again and make sure I pull a good vacuum using my micron gauge, and let it pull down with the pump on for at least an hour. I also need to change the oil in my Robinair SPX 4 cfm 2 stage pump. It's been a long time.

I'll be following this. I have had 134 systems at 33-35°F vent output, fan speed 2 or 3, recirc air, 105°F outside, high idle, Ford truck. Any colder and the unit can cycle off/on to prevent freeze up.

 

[roaniecowpony]

I'll be following this. I have had 134 systems at 33-35°F vent output, fan speed 2 or 3, recirc air, 105°F outside, high idle, Ford truck. Any colder and the unit can cycle off/on to prevent freeze up.

I think the JL system is pretty sophisticated and will prevent freeze up regardless of what refrigerant is in there.

 

[mwilk012]

I'll be following this. I have had 134 systems at 33-35°F vent output, fan speed 2 or 3, recirc air, 105°F outside, high idle, Ford truck. Any colder and the unit can cycle off/on to prevent freeze up.

It the vent output is in the low 30’s, evaporator temp is below freezing. Those systems were not operating correctly.

 

[roaniecowpony]

When I stopped by Johnstone Supply for some vac pump oil, I grabbed a couple cans of evap coil cleaner. Since the filter was that dirty, surely something got by and is covering the evaporator. I dumped most of a can into the plenum through the hole where the fan installs. It's a short distance over to the evaporator.

 

[roaniecowpony]

When I stopped by Johnstone Supply for some vac pump oil, I grabbed a couple cans of evap coil cleaner. Since the filter was that dirty, surely something got by and is covering the evaporator. I dumped most of a can into the plenum through the hole where the fan installs. It's a short distance over to the evaporator.

So, the evaporator cleaning was worth maybe 2-3 degrees in vent temperature. It's starting to work almost acceptably. But zero margin with 84F OAT it was able to get it comfortable if I had it on Max and the vents pointed at me.

 

[Jeffy56]

It the vent output is in the low 30’s, evaporator temp is below freezing. Those systems were not operating correctly.

I hear you. That's why the note of cold temp thermal cycling.

 

[roaniecowpony]

I think I'm done messing with the AC. I'm satisfied. Pulled it down to 500 microns for about 1 1/2 hours and charged it with R134a. This was cruising down the freeway.

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