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Only "moderately cooler" air conditioning

1K views 19 replies 7 participants last post by  johnniebravo 
#1 ·
So I've never been impressed with my ladies Laredo's HVAC system. Currently the max fan, circulating air, with AC on is only slightly cooler than ambient; definitely not suitable for 90+F (32 C) degree days.

I had to replace the compressor about 3 years ago. It worked okay, but not great even then. The charge is at full pressure and it holds it.

So any tips of what to look at next or how to improve the cooling?

When I replaced the compressor, the instructions did say to replace the dryer.... but I did not due to the extra time involved to replace it. Could this have that much of an adverse affect on cooling performance?

Otherwise maybe I need a new ac radiator(heat exchanger) if to make fins are damaged?

Any insight to get this addressed soon would be greatly appreciated.

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#2 ·
who recharged the system? if you used one of those do it yourself cans, that may be the problem. have a good a/c shop evacuate & refill the system. I had to have mine done twice before it got real cold. now it gets down to 42 deg on a 90 deg day. also, the r12 we used in old cars was much better than todays r134
 
#3 ·
not replacing the receiver drier generally voids the warranty on the new compressor. they want you to replace the drier because you can have metal shavings in there from when the old compressor seized that will kill the new one too.

how did you evacuate the system after replacing the compressor 3 years ago? if you did not pull and hold a full vacuum on the system after replacing the compressor, that's the problem
 
#4 ·
Ah, good points. I suspect the shop that replaced the compressor didn't vacuum down enough.

I have a vacuum, proper ac gauge/ line kit, and a bottle of good refrigerant, so I'll give that a shot.

Thanks.

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#5 ·
Well.....cr@p. That proved to be a waste of 2 hours and $60.

Fully evacuated the system into an empty tank. Vaccummed down to -29"H20, pressure held, continued to vaccume for 40 minutes. Put in two 12 Oz R134a cans. Low side pressure right at 60 PSI and high side around 200-250 (can't remember exactly, but for sure >150 and less than 250). But still the air coming out of the AC vents were only about 10 degrees F cooler than ambient like before.

So no leaks, compressor kicks in and pressures are right, but virtually no cooling. The low and high side pipes were both hot.

AC systems aren't that complex, so maybe I still damaged the compressor even though pressures are good?

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#7 ·
I assume you mean the ability to direct air out of the desired vent? If so, then yes, all fan speeds work, the AC kicks in when I hit the AC button, and I can select feet, feet/head, head, front defrost, and the two interior circulating options and the air moves to the correct vents.

Or are you talking about the hot/cold dial? I have kept it on the coldest option and haven't tried playing with that. I will check that though. Even if that wasn't working, shouldn't the low side line under the hood be cool/cold?

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#9 ·
Okay, the expansion valve seems like the next thing to check as the blend door seems to be working as I can go from slightly cool to hot in pretty good increments. I hear the air flow sound change as I move the dial throughout the range.

Driving highway speeds or stationary doesn't change the temperature at all, which rules out the ac radiator/heat exchanger in the grill.

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#10 ·
Well so changed the expansion valve....which I now remember that I replaced that when I had the compressor replaced 3-4 years ago. So recharged the system, but absolutely no change in cooling performance.

There is definitely some cooling effect, because if I turn the AC off, it goes to warm air (damn near 100 F today!). But the air coming out is only about 10-15 degrees F cooler than ambient.

So is it possible the blend door is out of position that the max cold doesn't have it moved to the max position? I'm leaning towards this now since the low side line was actually cool....or at least not hot like the engine this time around.


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#11 ·
Agreed that you need to check the blend door for air flow to be sure that the system is routing the warm cabin or outside air over the AC evaporator coil. If the air is not routed to the evap, the expansion valve most likely limit flow of refrigerant. Effectively, without airflow the coil freezes up. The expansion valve senses temperature differences between the refrigerant pipes that flow through it.



An equivalent of this problem is when you don't change your home AC air filter. All of the airflow is blocked. Your a-coil may freeze and the system doesn't work well. Your blend door is equal to the filter.
 
#12 ·
Yeah, looks like I'll have to break into the HVAC system to check the doors.

I did do a "calibration" of the system, but no change in cooling performance for me.

FYI for those that don't know (stolen from the thread below):
1. Put the key to the "On" position with the blower fan off.
2. Press and hold the rear defroster button
3. Turn the blower fan on (low is fine) while still holding the rear defrost button
4. After about 5 seconds the defrost button will start flashing and it'll start the calibration process of automatically switching through all the vent motor settings.
This thread has a lot of information: https://www.jeepforum.com/forum/f67/blend-door-repair-1215046/

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#13 ·
Do you have a dual climate control unit? If so, you may have a blend door issue.

I have almost the same issue as you but I have the single climate control, which I've not seen any blend door issues with them. Also, in mine, my drivers side has cold air but the rear and passenger side are warm. I've had it recharged at a shop and they suggested I try the expansion valve next.
 
#15 ·
Well, I think I found the problem...er, well, at least one problem: the plastic gear for the air-source flap (Blend doors?/A/C Air Actuator?) was broken.

I took the motor off and the sensor, but everything appeared fine. But putting it back together it seemed weird that the flap didn't catch on to anything attached to the actuator motor. After looking at Chirpz's instructions, indeed the gears were completely broken off. I didn't notice it because it was such a clean break and I didn't find any broken debris inside that area.

So I ordered a new aftermarket part from Amazon for $18 (68072190AA per Chripz's instructions).

That said, I'm fairly skeptical this will fix my problem of very poor cooling as I could manually hold the flap in one direction or the other and it didn't affect the temperature of the air coming out of the vents. But we'll see later this week after I get the part and keep my fingers crossed that this'll some how fix it.

FYI on the link the Chirpz's instructions (post 37 on page 3):
https://www.jeepforum.com/forum/f67/tech-write-ups-diy-write-ups-1480838/index3.html


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#16 ·
That should fix it, but before you put it in. Pull the fan out and reach up and check and make sure the blend door is working right.
On ours the pin that holds the door in place had broken. The door was just sitting there doing nothing.
I had to go to the yard to get another pin. Luckily they are all over the place and not hard to get out.
 
#17 ·
That should fix it, but before you put it in. Pull the fan out and reach up and check and make sure the blend door is working right.

On ours the pin that holds the door in place had broken. The door was just sitting there doing nothing.

I had to go to the yard to get another pin. Luckily they are all over the place and not hard to get out.
Dumb question, but is there a good diagram of this HVAC system? Would be good to know exactly what screws/clips to remove before blindly unfastening everything I see.

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#19 ·
Short version:
Absolutely no change in air temp with the re-circ door working properly......because it has nothing to do with the blend door! The blend door is actually behind the center console by the driver's (left) side in my manual-controlled HVAC system. However, that still isn't my issue either. So likely have to schedule a trip to the dealer......

Long version:
1. Door access - Not that it took long, but you don't need to remove the fan and bottom panel to check if the blend door is connected to the outside gear properly. Removing the glove box is easy (just two tabs to push down, 1 arm to unhook on the right side, and a yank off the hinge clips) and allows full access to the blend door motor and the blend door itself since there is a large opening for the recirculating air to come in. So you can move the outside gear with your left hand and either see the door move or feel it moving with your right hand through the cabin air side intake.

2. Gear replacement - I bought this from Amazon (https://www.amazon.com/gp/product/B07XKGTNXP/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) It isn't OEM, but I think much better as there is a lot of meat (plastic) holding the gear teeth on. Maybe not as good to tolerate mis alignment or tolerance changes, but it isn't going to break anytime soon.....and if it does you get 2 of them! I did do a re-calibration again after I replaced the gear since I did it before without the gear.

3. Blend door location - This video shows you where/how to access the actual blend door: Super easy to get to. Just pop the cover right under the steering column down. Let is swing to the lowest point then yank off the hinge. The blend door motor is the lower one closest to that panel. 2 T20 torx and the motor pops right off. However, my motor turns just fine and the gears/attachment mechanism doesn't appear to be broken. I could definitely manually move the blend doors with the connection on the outside of the HVAC system. So again, starting the jeep and holding the blend door in one direction yielded hot air and flipping the door completely in the other direction yielded my "slightly cooler air".

So everything all seems to be checking out. Might have to schedule a trip to the dealer in the near future as going without AC right now kinda sucks.
 
#20 ·
Looking back you mentioned that both the small and large lines are both warm to the touch. Are they always like this? The high side line should be cold and sweating if the AC is on.

Do the pressures fluctuate as the AC compressor cycles on and off? Is the condenser new or is it the original?

If the system is truly calling for cooling and both lines are hot I would begin to think a restriction is present OR the compressor isn't working properly.

The last possibility is the ecu/hvac control is malfunctioning and calling for a warmer air temperature even though the AC is working well.

Are the pressures you reported appropriate for the ambient temps?


Sorry for all of the questions, but something (hopefully small) is off. Its just a matter of sorting things out. There are only a few parts to the system, its not terribly complicated.


Charge seems OK because you added only 2 cans and the expansion valve is presumed OK cause its new. How about the drier? Was it changed? Are all the tests done with the vehicle moving or stationary?
 
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