Get ready for this a/c question - JeepForum.com
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post #1 of 9 Old 07-10-2019, 03:00 AM Thread Starter
Peter1969
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Get ready for this a/c question

2000 4.7 limited
I’ve replaced the entire ac system and cooling system including clutch & fan and electric fan, switches, hoses/lines.. everything!
So hood sticker says 24 oz with 5.75 pag oil. Ok. Did that. Both high/low psi were low. Maybe 60 at vents. Not good.
Ran up rpms from under hood and low would go down to 20ish and cut off the compressor. Drove it 10-15 miles at different speeds. No change. Clearly low on r-134 I’m thinking. But I got the right amount in. All ac parts were OEM and looked the same. So, figuring I have the equipment to vac and recharge, I added 1-2 sec bursts of r-134. Wait a few, rev it up to watch low psi. Did this 3 times til evap lines & accumulator started to get could and wet. Vents was at 44-48 at idle with 95 weather. Drove it and was cold til I reached 60mph then it was 60 at vents. Another quick burst and goes to 65 mph before cutting out. Did this a few times and many miles later I got it to 56 at 65mph and left it like that so I could regroup. Can anyone make sense of why I have about 30oz in a 24 oz system on hood tag? I still have to add another squirt or so. My low was 30-35/ high was 200-235 at idle. I was told the best ac cooling is on hwy and it’s worst at idle. Mines the opposite right now. So I’m in the ball park.
Whatcha all thinks going on putting more than mfr specs? Is it a wj Jeep thing? I’m stumped

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post #2 of 9 Old 07-10-2019, 08:52 AM
99sajeep
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Quote:
Originally Posted by Peter1969 View Post
Vents was at 44-48 at idle with 95 weather.
My low was 30-35/ high was 200-235 at idle.
Your temps at idle are pretty good, but based on your pressures, it appears your system is low on freon. What do the pressures look like with engine revs at 2000-2500 rpms?

At 95*, your low pressure should be around 50 psi (+/-) and your high pressure should be around 280 psi (+/-). If it was me, I'd fill up to those pressures and call it good. I trust the working pressures more than I trust the label quantity.
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post #3 of 9 Old 07-11-2019, 03:23 PM
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Does your low side pressure ever go into the negative? If so you could be fighting a failing expansion valve
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post #4 of 9 Old 07-11-2019, 04:13 PM Thread Starter
Peter1969
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Sorry guys I didn’t get an alert that anyone replied.
The low psi doesn’t doesn’t draw down past 20psi when low pressure cuts compressor. But liquid line is new, as well as everything else. Can feel temp difference on each side of orifice tube.
Those psi for low/hi in 95 weather 50/280 +_ that was listed,,, was that at idle or 2-2.5k rpms??
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post #5 of 9 Old 07-11-2019, 05:17 PM Thread Starter
Peter1969
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We only tested at 1500rpms. So we noticed at 2k she would draw low side down to 20 and cut comp. So I basically put a 1-2 sec squirt in, held rpms and repeated til she held around around 25psi at 2-2.5k rpms, and didn’t cut comp. Prolly another 3-4 oz. So at 2k rpms 25/300. 2.5k rpms 25/325-350. Idle was 35/225. I stopped there because both accumulator lines from firewall to comp had frost on it. I watched it form and freaked my out. So I stopped lol.
I realized a few hours later last night that the weather did drop about 5-10 degrees, and more importantly (I think) is he cabin had been cooling during all these tests, windows up and in recirc. and prolly caused frost due to r-134 not having to work in evap with really cool air blowing through it. I dunno.
Soo, today, 90-95 weather I did static test and got 115 on both h/l. Great! Idle was 35/225. Went ahead with 1-2 sec squirt and both 2k and 2.5k rpms had low at 35 and the high would start around 375 and settle at 350. Vent temp was 50 and with rpms maybe 48 parked. When I drove it it was good til 60mph which is around 2k rpms, vent rose to 56-60. Same for 70 which is around 2.5rpms. So thinking the last squirt overcharged it.
I did another squirt idle is 35/225-250 52 at vent. Then the vent temp dropped to 50-48 at 2-2.5k rpms. Great I thought. Psi at 2k was 30/375 and 2.5k was 30/ and just under 400. That’s parked. Well I drive it and she’s good til 60mph or more with vent temps at 56-60 again.
I dunno bout near 400 psi on hi side, or if 400 is hi cut off limit. I’ve yet to see low side go above 40. At idle after coming down from 2.5k she’ll sit at 40 for a bit then wind down to 35psi. My idle psi is the highest I’ve seen it at 35/225-250.
I’m inclined to add more as she should stop cooling if I overcharged it, or tripping hi side switch.
If all my stuff wasn’t new I’d think I had a blockage somewhere like orifice in liquid line. The high side would get a lil higher with each squirt, and took low side maybe 5-8 squirts to get it from 25 to 35. Shouldn’t it be 45-55/250-300 at idle in 90-95 weather. Or is that with rpms? If that is idle psi, the way it’s been going getting low to come up another 10 psi would raise hi side past 400 for sure. Guessing 425 or so. Doesn’t that seem too high?
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post #6 of 9 Old 07-11-2019, 09:17 PM
99sajeep
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Those psi for low/hi in 95 weather 50/280 +_ that was listed,,, was that at idle or 2-2.5k rpms??
Should be at idle. I just had to replace a low-side valve core on my WK so I had to replace the R134 in the system. Idle pressures were right at 55/290 (low/high) psi and the vents were blowing a steady 45*F on high fan. Outside temp was just over 90*F.

I'm at a loss now with what your pressures are reading.

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post #7 of 9 Old 07-11-2019, 11:24 PM Thread Starter
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I’m at a loss as well. I know my posts are long and I apologize! Really! This is beyond logical for me. My god! Lol
I replaced ac parts because I thought they were bad, mechanics kept saying age of ac parts, fans, etc.. and would stop at 28 oz per hood sticker. Dealership did evap last summer and I replaced the rest. But even with the old ac parts and fans I had the same scenario, cold at idle and driving until 60mph or more and vent temp would get warmer. Maybe 5 degrees or so cooler with new parts but still warmer on the highway doing 65-70 mph, than at idle up to those highway speeds. Like 10 or more degrees difference. Mechanics kept saying maybe orifice in liquid line, fan clutch, ac fan etc.. Well I took those variables away by replacing all the parts of ac and engine cooling system. Engine temps are fine btw. Sooo, it was just a matter of pag oil at 5.75 and 28 oz of r-134a. Evap was the only part that could’ve had pag oil in it as I replaced everything else. Drained oil from new comp, I estimated 2oz was in evap and made up the difference adding some to comp, accumulator, and condenser. It didn’t cool below 60 degrees at idle or hwy. So I added more, it got cooler both at idle and hwy, but hwy was and still had higher vent temps than at speeds below 60mph down to idle. Idle to 45 mph has coldest vent temps, with old parts &new, it’s been the same scenario. Again new parts are a lil cooler.
I’m overcharged now for sure. Just got back from night drive at 80 weather and I’m at 56-60 at vent.
I’m gonna vent it down til I get the frost back on accumulator lines and comp suction side at 2-2.5k rpms. That was the best I got. Gotta compromise for now and cut my losses as far as trying to understand this. When I had frost my low/hi psi’s were low according to charts. I had 44-48 from vent at idle to 50 mph and 52-56 degrees on hwy at 70 mph, with 90 ambient.
Orifice is colder on firewall side and can visibly see condensation at that point in the line. Evap in/out lines cold, hard to tell which is colder but it seemed the outlet side was colder, and comp suction seemed colder than both of them. First time i saw frost form it started from accumulator line to compressor. By the time my eyes Crazy! I was taught hwy should be optimum ac temps and idle in traffic at it’s worse.
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post #8 of 9 Old 07-12-2019, 12:00 AM Thread Starter
Peter1969
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By the time I followed the line to the compressor it was already frosty, so not sure where it starts. Take my psi readings after fan clutch has disengaged at rpms and electric fan is always at high speed in this heat. All the charts I’ve seen online I assume are at idle. I’m 10-15 psi below that on low side at idle. 35/225-250 at idle then 30/near 400 at 2.5k rpm 90 ambient. Unless the high switch is 450 or something I’m letting some out til she frosts.
As stumped as I am, I do feel it’s something simple. Either a bad part, or me not doing something right.

I do need someone to confirm that ac cooling is at optimum at hwy speeds and better than stopped/traffic please???
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post #9 of 9 Old 07-12-2019, 12:13 AM Thread Starter
Peter1969
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Just remembered last summer with old parts and before I bought manifold gauge I did charge low side with diy gauge/r-134 can to 50 psi in 95 ambient. Few days later I notice green on hose from accumulator to compressor where metal couplings meet rubber hose. Drained some out, colder at idle to 50 mph, then warmer. Though actual vent temps are cooler with new parts, but that’s been her trend,
Read about compressor types and I have no idea. It’s a denso, looks just like the old one. Online store matched it to my Jeep. Maybe something between low and high switches to “computer” doesn’t jive?
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