Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Friendly format provided to inquire about automotive a/c systems.
Archived Forum

Moderators: bohica2xo, Tim, Dougflas, HECAT

AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Sat Jun 24, 2017 12:12 pm

Hi everyone, I had another thread on here recently, and after replacing all A/C components this weekend, I have no improvements in outlet temp. Here is the history:

2006 Lincoln Navigator w/rear (aux) A/C. Bought it in April 2016, with 110k on the odometer. Seemed to be taken care of pretty well.

Summer of 2016, I noticed the A/C wasn't performing well. Especially when I wasn't cruising down the highway for a bit. I added R134 with a quick re-charge kit, and low side pressures wouldn't come out to where they should be in the 85 degree (Fahrenheit) ambient temperature. Added more refrigerant and ended up blowing the seal on the front of the compressor. I then did the following:

Installed a new Four Seasons compressor
Installed a new condenser
Installed new Four Season TXV's (front and rear)
Installed new Four Season drier/accumulator
Installed all new o-rings

I had flushed the lines and the evaporators, and blow them dry with dry air @ 90 PSI. The new compressor was completely drained of PAG oil, and I installed the compressor along with the condenser, drier, and TXV's. Filled the compressor with dyed PAG 46 oil (14 oz, the per the specifications) via the low pressure line. Took the truck to my buddy with a Snap-On A/C machine to do a 30 minute vacuum and filled with 3.6 lbs of R134. In 78 degree ambient temp, truck wouldn't get lower the 50 degrees outlet temp while idling, nor lower than 45 degrees while cruising down the highway. Didn't matter how many hours I drove with the A/C blasting.... 45 degrees outlet temp was the best I'd see. The warmer it got outside, the poorer the A/C system performed. On 90 degree days, I was only seeing 50-55+ degrees outlet temp on recirc mode.

Frustrated with the poor performance of the A/C system after everything I did late last year, I just ordered all-new everything:

Motorcraft evaporators with gaskets (front and rear)
Motorcraft TXV's (front a rear)
Motorcraft compressor
Motorcraft condenser
Motorcraft muffler line
Motorcraft accumulator/drier
Motorcraft fan clutch
Motorcraft fan blade
Motorcraft blend door actuators (2 for the front [dual zone climate control] and 1 for the rear)
Motorcraft evaporator temperature sensor (front)
2 - 12" puller fans mounted to the back side of the condensor (to hopefully help with outlet temps while idling)

All lines under the hood were brand new this time, so I flushed the lines that ran to the rear A/C system, blew them dry with dry air again, installed the evaporators, TXV's compressor (did the same as last time--- drained it completely before installing it), installed the new condenser and drier. I was sure not to allow the drier to be exposed to the atmosphere after unboxing it. It got connected the the sealed system immediately after install, once I removed the shipping plugs from the lines. I added the 14 oz of PAG oil again, and once again, took the car back to my friend. He did another 30 minute vacuum and charged with 3.6 lbs again. 83 degrees outside ambient temp, and pressures were spot on, but the system would only get to around 52 degrees outlet temp while idling and still only as good as 45 degrees after driving with the system full-blast for a while out on the highway.

I beyond frustrated with this A/C system. I pinched off the heater core lines on the front and the rear to see if heat was somehow bleeding past the blend doors) and both the front and the rear A/C system were within 1 degree of each other on the outlet temp, but neither system would get below 47 degrees yesterday while driving. I then checked the rear evaporator temp (it's easier to check than the front, since I still have the interior panel removed) and it was around 70 degrees. I had checked the front evaporator a couple months ago and it was only around 68 degrees. What gives???? And how is it that the evaporator temperature is only around 70 degrees, but the outlet temp at the time was around 50 degrees???? Should the evaporators be a lot colder???? They didn't feel cold at all. And the heater core lines were nice and cool since the lines were pinched off, so there's definitely no heat bleeding into either evaporator plenum. We added a little more refrigerant and no improvements, so we evacuated the system and re-charged it back with 3.6 lbs.

The recirc door for the front A/C is definitely operating properly and the rear A/C can only recirculate cabin air (it has no means of bringing in outside air). I just don't get it. Do the TXV's need to be adjust or something????

I know several people will say 45 degrees outlet temp is just fine.... but I've never owned a Ford (and I've owned plenty) that won't put anywhere from 38-40 degrees outlet temperature sitting still, let alone while driving down the highway for a while. No other car I've owned out of the 13+ cars have I had to do any work to get cold enough temps to come out of the vents. My '98 Expedition was 39 degrees all day long and I never even replaced anything on that A/C system. And that 45 degrees outlet temp is unattainable once it gets hotter outside. Outside air is definitely not getting into the evaporator plenum so nothing explains the poor performance I'm seeing. Does anyone have any ideas at all???? Thanks a bunch!!

-Andrew
AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Tue Jun 27, 2017 3:40 pm

Does anyone have any ideas/suggestions?? Thanks a bunch!
User avatar
Cusser
Posts: 432
Joined: Sun Apr 24, 2016 6:29 am

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby Cusser » Wed Jun 28, 2017 9:03 am

45F coming out the vents is pretty good. That's what I measure on my vehicles (1998 and 2004 Frontiers, and 2005 Yukon), and those keep us pretty cool, in Arizona.
AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Wed Jun 28, 2017 5:01 pm

How does 62 degrees sound on a 93 degree day, in recirc mode?? Haha. That 45 degrees is also only if I'm barreling down the highway for 15+ minutes. Otherwise, if I'm sitting in traffic, that same day I see 45 blasting down the highway, I only see 54 or so sitting still. And 60 degree days... I've seen 43-44 at spurts, but usually still 45. I absolutely will not see 45 when on days hotter than lately, and to me, there is clearly a problem somewhere.

And no to be repetitive, but I've never owned a Ford with R134A that hasn't seen 40 degrees or colder out the vents. I've owned 13 or 14 cars now, since 2001, and this is the first one to not blow cold enough air while running down the highway, and to perform like total crap when crawling in traffic. Outlet temps increase around 10 degrees when sitting in traffic, or parked. And that's even with the new 12" puller fans (mounted directly to the condenser) running. My '98 Expedition with rear A/C put out around 39 degrees in 90 degree whether, sitting still or driving down the highway. 45 degrees while barreling down the highway for 2 hours with the A/C full-blast and on recirc mode, on an 80 degree day just can't be right. And the compressor isn't even cycling off often, so it's not like it's cycling off before the temps have a chance to get too cold for the evaporator.
User avatar
Cusser
Posts: 432
Joined: Sun Apr 24, 2016 6:29 am

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby Cusser » Wed Jun 28, 2017 8:57 pm

AGrayson84 wrote:How does 62 degrees sound on a 93 degree day, in recirc mode?? Haha. That 45 degrees is also only if I'm barreling down the highway for 15+ minutes. Otherwise, if I'm sitting in traffic, that same day I see 45 blasting down the highway, I only see 54 or so sitting still. And 60 degree days... I've seen 43-44 at spurts, but usually still 45. I absolutely will not see 45 when on days hotter than lately, and to me, there is clearly a problem somewhere.


Sounds like an air flow issue across the condenser. You said new fan clutch, did that test "good"? Got all fan shrouds?
User avatar
bohica2xo
Posts: 611
Joined: Wed May 11, 2016 4:12 pm
Location: Las Vegas, NV

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby bohica2xo » Thu Jun 29, 2017 8:09 am

All I see are temps, not pressures. Assuming you have enough compressor & condenser capacity, something is not working well.

You mention cycling. I have had an issue with too much hysteresis in a ford cycling switch. Pressures will show this clearly.

Here in the desert I install adjustable cycling switches - I can run a colder condenser when the humidity is 3% My pickup has two switches set to different pressures.

For road pressure readings duct tape the gauges to the outside of the windshield & have someone write down the data...
atikovi
Posts: 31
Joined: Wed Jul 06, 2016 3:01 pm
Location: Suburban Washington DC

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby atikovi » Sat Jul 01, 2017 8:51 am

AGrayson84 wrote:we evacuated the system


For how long? Was this in a shop setting where time is money and they just vacuum for 15 minutes?
AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Mon Jul 17, 2017 7:29 pm

Hi everyone, thanks for your continued help on this. I've been tied up with a bunch of other things lately and just recently have gotten back into troubleshooting this issue. I know my posts are very lengthy, and here comes another one, but it hopefully includes all the important details you all are looking to know.

Cusser wrote:
AGrayson84 wrote:How does 62 degrees sound on a 93 degree day, in recirc mode?? Haha. That 45 degrees is also only if I'm barreling down the highway for 15+ minutes. Otherwise, if I'm sitting in traffic, that same day I see 45 blasting down the highway, I only see 54 or so sitting still. And 60 degree days... I've seen 43-44 at spurts, but usually still 45. I absolutely will not see 45 when on days hotter than lately, and to me, there is clearly a problem somewhere.


Sounds like an air flow issue across the condenser. You said new fan clutch, did that test "good"? Got all fan shrouds?


Yep, all shrouds are installed. I'm not experiencing the basic diagnostic examples of good fan clutch.... my new clutch continues to spin more than my previous one did after shutting the engine off when the engine is hot, but it has a bit of resistance when turning by hand when the clutch is cool. The fan is generally never loud... it stays relatively quiet at all times. Perhaps Motorcraft designed this clutch a little differently than most other vehicles floating around out there, being that this is a Navigator and they didn't want to have a noisy fan. My buddy who works exclusively on Fords (used to work at a dealer, now has his own shop) has heard mine and says it sounds to quieter than any other 2nd generation Expedition or Navigator he has heard. Regardless, it's a brand new clutch and fan blade assembly from Motorcraft so I can't imagine the clutch being the problem. Radiator is clean, and I've also added two staggered 12" puller fans, attached directly the back of the condenser (mentioned in my first post in this thread), and they don't seem to make a difference when they are running. They lower the high side pressures a bit, but I don't end up seeing significantly cooler air coming out of the vents as a result. The longer I sit, the higher the outlet temperature climbs, regardless of the ambient temperature and cabin temperature. I can usually expect the outlet temperature to increase around 10 degrees once the car has sat idling for a few minutes, or crawling in traffic.

I think some of this has to do with my idle speed being around 550 RPM when in gear. I guess the compressor doesn't spin fast enough during in-gear idling, since the electric fans and new fan clutch assembly doesn't seem to help. This is a common idle speed on these 5.4 engines, and I have a brand new Motorcraft throttle body, cleaned my MAF with electronics cleaner, new air filter, all new accessories and pulleys on the front of the engine, PCV isn't clogged, etc. etc. Idle speed has been this low since I first bought the car, prior to doing/replacing what I just mentioned.


bohica2xo wrote:All I see are temps, not pressures. Assuming you have enough compressor & condenser capacity, something is not working well.

You mention cycling. I have had an issue with too much hysteresis in a ford cycling switch. Pressures will show this clearly.

Here in the desert I install adjustable cycling switches - I can run a colder condenser when the humidity is 3% My pickup has two switches set to different pressures.

For road pressure readings duct tape the gauges to the outside of the windshield & have someone write down the data...


OK so I gathered some pressures yesterday.

Windows up and doors closed, front and rear A/C systems at the coldest setting and fans on the highest setting, recirculate mode turned on, engine speed brought up to ~1400 RPM for 90 seconds. Pressures were 26 / 195. Ambient temperature was 83-84 degrees at this time.

I then ran the manifold gauge set through my passenger's side window and my friend did some video and pictures. After driving for 2 minutes, with the same configuration as the 0 MPH test above, I was seeing about 25 / 157.

Here is a video of this drive:

https://www.youtube.com/watch?v=Qpo74SdsdIU

Ambient temp was about 84 still, and idle speed was about 1600 or so RPM on average. Compressor stayed running this entire time... it did not cycle off, which you can see watching the gauges.

What do you all think about these results??? Outlet temp crept down to about 47 degrees during this test if I recall correctly, but that was because I had already been driving with the A/C blasting for 45 minutes at this point ,which finally cooled the cabin down enough to allow for that kind of outlet temperature. Prior to that, the car was parked in the shade in the 84 degree weather... and took every bit of 25 minutes of driving to get down to outlet temperature in the low 50's. The interior was far from being hot inside when I started all of this yesterday.


So what do you guys think of those results??


atikovi wrote:
AGrayson84 wrote:we evacuated the system


For how long? Was this in a shop setting where time is money and they just vacuum for 15 minutes?


This last time was a full evac, and then a 30 minute vacuum with no vacuum loss after sitting for another 30 minutes. I've left my RobinAir machine on this car for 5 hours previously, and even that ridiculous amount of time has not improved the A/C performance when re-filling the system after. We both have 6 CFM vacuum pumps.... so they're not like the little crappy ones you can rent from AutoZone.
AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Mon Jul 17, 2017 7:50 pm

So late last week, we had our first really hot day. It was about 98/98 degrees outside. The car was not in the shade, sitting in a parking lot with my Covercraft windshield visor and tinted windows, so the interior was definitely hot still, but not exactly baking. I started up the car with the front and rear systems on full blast, recirc mode, etc. I let the car run for about 15 minutes. When I got in the car, outlet temperature was 71 degrees. Needless to say the interior was far from cool, with only 70 degree air to battle the nearly 100 degree ambient temperature. I made it out to the main road to go home and just before hitting the crawling traffic I had reached about 63 degrees on the outlet temp after 5 minutes of driving. Once I hit the traffic where I was anywhere from 0-10 MPH, I could watch the outlet temp increase. Outlet temps reach 73 degrees and wouldn't budge until I could get moving at a better speed. Again, I suspect not so much an airflow problem across the condensor (new fan clutch assembly, two 12" high-velocity puller fans), but rather my low in-gear idle speed contributing to this. But still, only 73 degrees out the vents a few minutes after the car had cooled down to 63 out the vents........ granted I wasn't putting out heat from the vents, that was just not doing it, and here I was, an hour after the car had been running, still in stop-and-go traffic, now down to around 69-71 degrees outlet temp because I was moving anywhere from 5-15 MPH at this point. Still not enough to battle the heat. I'm sweating in my car, after my A/C has been running for an hour. Regardless of the fact that it was almost 100 degrees out, the car should have cooled down enough to produce much cooler temperatures after an hour on recirc mode. Any other car I've owned or driven in, even mid/late '90s cars that had R134A from the factory, including an equally-sized '98 Expedition with rear A/C also, has done WAYYYYY better than this.

The cooling performance is just so poor on this thing. I understand that in recirc mode on a hot day you have to remove the heat and humidity from the cabin in order to build cooler outlet temps.... but even taking 35+ minutes of driving down the highway in 85 degree weather to slowly get down to 45-47 degrees outlet temp, when the cabin was not heat-soaked, is just not good at all..... let alone the A/C running for an hour in 98 degree weather and only about to make 73 degree outlet temperature.

Something is obviously wrong here. No coolant is running through the heat exchanger. I can clamp off the inlet and outlet lines to the heat exchanger, and even though the lines to the exchanger remain cool, confirming that no coolant is flowing, the front and rear A/C systems are still performing the same. The rear system only does recirculating air, and the front system has been confirmed to be blocking off exterior air when in recirc mode, so there is not heat source entering the front nor rear plenum to increase the temperature of the air leaving the plenum.

All lines that weren't brand new have been flushed. Condenser, compressor, muffler, filter/drier, evaporators, TXV's..... all that have been replaced with new Motorcraft parts. Lowe pressure lines coming from the evaporators are both sweating.... there's no frost building anywhere..... everything points to a properly functioning system.
AGrayson84
Posts: 26
Joined: Sun May 14, 2017 6:47 pm

Re: Evaporator temps around 70 degrees, vent temps only 45 degrees at best

Postby AGrayson84 » Mon Jul 17, 2017 8:03 pm

Does anyone here understand super-heat and sub-cooling?

I've been talking to my buddy who does residential and commercial A/C work for a living. He's been doing it for over a decade. He admits to not knowing about automotive A/C systems, but he has been dealing with R134A for quite some time. He uses an app daily to calculate what his super-heat and sub-cooling should be. He recorded my pressures and said that 25/26 PSI on the low side should be within range, as based on the boiling temperature that you would see at 26 PSI, the evaporator temperature should be around 37 degrees. I'm going to try to check the temperature on the low pressure side of my rear evaporator tomorrow, since the interior panel is still removed, and see what I get there. I figure it will be better to check the temperature on the rear evaporator line, since the front evaporator line is always heat-soaked from the engine bay. I don't feel like I'm going to see anywhere near 37 degrees, and the rear A/C puts out just about the same outlet temperature as the front A/C at any given time.

I don't think anyone doing automotive A/C work takes super-heat and sub-cooling numbers into effect, even when troubleshooting systems, but my friend says that for any given pressure, there will be a specific evaporator temperature to expect, and at any given evaporator temperature there will be a specific pressure to expect. Apparently my pressure seems spot-on for a sub 40-degree evaporator, yet I can't see within 5 degrees of that coming out the vents to save my life.

Any input on this? Thanks again everyone!!

-Andrew

Return to “Automotive Air Conditioning Forum”