"Max A/C"

[roaniecowpony]

Lately the coolest output is close to 40°F center passenger vent. Ambient 94-98°F. Recirc on, 5000'. Recirc should give slightly higher fan out with a clean filter. I've rebuilt and/or upgraded a R12 and a couple of R134 systems. I would suspect the 1234 system will operate at higher pressures. My cabin air filter has been changed twice in 1 1/2 yrs and 14K miles. I'll check calibration of the analog thermometer, which was a good grade unit. My overall view of the system is it's marginal. I will run the "max cooling fan" Tazer option when I'm near the next destination. 2018 JLUS, 3.6, 62K miles. Calibration is good, as seen in last pic.

Thanks much. That's right about what I'm getting on the vent temp. I've done some AC work over the years as well. I agree, the JL system seems marginal. I'm giving some consideration to painting the hardtop to match my Billet Silver body color. With a IR thermometer, the temps are about 15-20F cooler in direct sun just now. The black top currently shows temps as high as 178F. Maybe a gutter clamp-on roof rack-shade?

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[roaniecowpony]

I was giving some thought to recharging with R134a to see if I could get lower temps. I need to check JSCAN for my evaporator temps and also look at my truck and wifes R134a temps.

 

[dstevens]

As far as I know 'max ac' is a shortcut to max fan speed, min temp and recirc on. Manufacturers have problems with mold for people who live in wet climates and also run on recirc, so the vents will switch recirc off after set timer periods to prevent this. Not sure if Jeep does this but most other manufacturers do.

Also there is some trickery with the sunlight sensor on the dash so that the AC does not run hard when in fuel economy testing.

44-46F is not great but it should be sufficient if the ambient is under 100F. From memory mine was 36F, but it depends on the ambient and also vehicle speed. At idle don't expect the same cooling as at speed.

What I suggest is to get an AC vent thermometer and stick it in a vent so that you can keep an eye on the temperature.

With my JK the expansion valve failed and so the AC would work great until you changed the air flow over the condenser and then the valve stuck, and so the cooling stopped. The vent thermometer helped a lot of diagnose that.

Finally, as far as I know R134A pressures are close to 1234, but without the honeywell patent the cost is 1/10th.

 

[dstevens]

Oh and if you need a vacuum pump and manifold for 134 let me know. You'll need adapters for the 1234.

 

[roaniecowpony]

As far as I know 'max ac' is a shortcut to max fan speed, min temp and recirc on. Manufacturers have problems with mold for people who live in wet climates and also run on recirc, so the vents will switch recirc off after set timer periods to prevent this. Not sure if Jeep does this but most other manufacturers do.

Also there is some trickery with the sunlight sensor on the dash so that the AC does not run hard when in fuel economy testing.

44-46F is not great but it should be sufficient if the ambient is under 100F. From memory mine was 36F, but it depends on the ambient and also vehicle speed. At idle don't expect the same cooling as at speed.

What I suggest is to get an AC vent thermometer and stick it in a vent so that you can keep an eye on the temperature.

With my JK the expansion valve failed and so the AC would work great until you changed the air flow over the condenser and then the valve stuck, and so the cooling stopped. The vent thermometer helped a lot of diagnose that.

Finally, as far as I know R134A pressures are close to 1234, but without the honeywell patent the cost is 1/10th.

I had a Thermapen instant read thermometer in the vent for some street and freeway driving several times now. Temps are 44-46 pretty consistently in the past couple weeks, including yesterday around here. Doesn't seem to change much, so I think the mechanicals and sensors are working as designed. My vacuum might have been less than ideal.

I was thinking about R134a, because my other vehicles seem to run cooler at the vent and R134a parts and labels are available for the JL, including the charging data in my factory service manual...and I have a lot of R134a

 

[jeepingib]

I know that you had the system open for a while when working on your engine. Did you replace the air dryer? Did you vacuum it for a decent amount of time to boil off the moisture in the system? The temps you are seeing are what I would expect if the system had moisture in it.

 

[roaniecowpony]

I know that you had the system open for a while when working on your engine. Did you replace the air dryer? Did you vacuum it for a decent amount of time to boil off the moisture in the system? The temps you are seeing are what I would expect if the system had moisture in it.

Yes, I had to replace the condenser, which comes with a new desiccant pack. That condenser was OEM plugged until the time I hooked it all up and vac'd it down. I did a shortcut on the vacuum, probably only 5 mins. I get what you're talking about. But if I draw it down again, I'm going to refill with R134a, since I have it, the fill specs, and some adapters. If I like it, I can buy the two lines with the R134 fill ports and the sticker from Mopar.

 

[roaniecowpony]

It's likely my cabin filter is responsible for carrying off a good portion of the dirt missing from the Rubicon trail and some Moab and Big Bear trails. I haven't looked at it since starting rock crawling a couple years ago. Also, I noticed the Jeep is leaning slightly on that side where the filter is.

Soooo, these pix speak for themselves. I hope the Rubicon Trail Foundation doesn't ban me for taking their trail dirt home. Looks like there's some Moab in there too, and enough hair to re-hair a dog. Quick question; are original 2018 cabin filters collectable?

 

[jeepingib]

Yes, I had to replace the condenser, which comes with a new desiccant pack. That condenser was OEM plugged until the time I hooked it all up and vac'd it down. I did a shortcut on the vacuum, probably only 5 mins. I get what you're talking about. But if I draw it down again, I'm going to refill with R134a, since I have it, the fill specs, and some adapters. If I like it, I can buy the two lines with the R134 fill ports and the sticker from Mopar.

I don't know how well that will work. I haven't had any experience with R1234 yet. But I know that it runs higher pressures than R134. So the issues I see if you don't convert anything may be that your switches will not turn the compressor or fan on and off as they should because of the difference in pressure. And the orifice may be different for the different type of refrigerant, I know that this was the case when we went from R12 to R134.

 

[roaniecowpony]

I don't know how well that will work. I haven't had any experience with R1234 yet. But I know that it runs higher pressures than R134. So the issues I see if you don't convert anything may be that your switches will not turn the compressor or fan on and off as they should because of the difference in pressure. And the orifice may be different for the different type of refrigerant, I know that this was the case when we went from R12 to R134.

Everything I've read about R1234yf suggests that the orifice does not need to change. Pressures are slightly higher with R1234yf. I didn't find a different orifice listed for R134a in the JL parts lists online. My only concern is possibly programming of the PCM for the different pressures/clutch operation. But, then everything I've read thus far suggests there should be no differences.

So, a test drive after the filter change and no surprise, it was a huge difference in flow rate. However, the ability to cool the cabin didn't change much and the vent temps jumped up to the low 50s while sustained rpm was 2200 ish and outside air temps were in the mid to upper 80s. Upon stopping for a light, the cabin temps got uncomfortable quickly. So, I'm going to find out if R134a is a straight change out. There is a slight increase refrigerant weight called for with R134a in my Tech Authority service manual.

 

[Jeffy56]

Additional info. Today, dynamic. My perception, higher vent fan speeds are sustainable. First pic, fan 6, second, fan 8. Ambient as shown. Road speed 38-40 mph, 1800-2300 RPM. 7 gear common. (4.10/32.6"OD)

 

[mwilk012]

So, what exactly did you charge your A/C system with?

There is something wrong with your Jeep. 1234 performs very well.

 

[zouch]

this is really interesting to me, as we've left our Climate Control on 'Auto' pretty much 100%, and the only time it's gotten to where the AC has gotten close to not keeping up is when we've been jumping in and out of the J**p on trail in the Dez when ambient temps have been in the hunnert-and-teens.

what i'm curious about is if any of y'all looking for more 'cool' have hard-top roof liners? i'm convinced ours makes a difference in the thermal insulation of the cabin (as well as the sound dampening).

 

[roaniecowpony]

I was just trying to determine if I needed to evacuate my system again and draw a better vacuum for longer to outgas moisture out of my AC system. I've concluded I do need to do that as it's not cooling per spec.

 

[roaniecowpony]

So, what exactly did you charge your A/C system with?

There is something wrong with your Jeep. 1234 performs very well.

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

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