A/C Help

[won4run]

Hey all,

My A/C hasn't been cooling as well as it should over the past couple of summers, but I've just dealt with it as I couldn't quite figure out what was wrong. I've read through the various A/C threads on here and looked at the factory service manual, but still can't nail down the issue. It will cool over time as it re-uses the cooled air. With 90F outdoor temps, vent temps decrease from 60F to 45 F after 15 mins of driving, but when I open the doors and windows the vent temps increase back to 60F.

04 V8 Limited with dual climate control ~ 175,000 miles

Here's what I've done so far:

1. Checked pressures:
Outside temp: 86 F
Vent temp: 60F
220 psi (15 bar) HI side
30 psi (2.2 bar) LO side.
Compressor off pressure is ~ 90 psi.
From my interpretation of the factory manual, the pressures look to be correct, but I could be wrong here.

2. Checked HVAC diag mode:
Code 33 was displayed for air outlet damper position sensor circuit
I do hear this hunting sometimes, but don't think this is causing the issue as this should just divert the air from face to the floor.

3. Recirculation actuator: I can hear recirculation actuator working as the air changes tone with it on or off.

4. Added UV dye and checked for leaks. I checked everywhere I could access and could not find any locations of leaks. Suspecting the evaporator, I also looked at the condensate drain line to see if any UV dye showed there, but did not see anything.

Any help or advice would be greatly appreciated!

 

[Kevin G.]

Check this.....

What does sight-glass look like?

Kevin

 

[won4run]

Mostly clear while running. I'll try to get a picture. The service manual was a bit confusing on what it should do, but from reading here I've gathered it should be clear while running and foam up when the compressor is turned off. Is that correct?

 

[November Sun]

Have you changed out you cabin air filter lately, I just did mine, must have been the original, full of leaves, dirt and was almost black. Now my air blows great and even cools better.

 

[won4run]

I took it the filter out and cleaned it and it definitely looked like yours. I'll get a replacement for it tomorrow. Thanks for the tip.

 

[81runner]

If I'm not mistaken, your low side pressure with r134a should be around 40 psi with the pump running at an ambient temperature of 80°F or higher. I would try adding a little charge to it.

 

[81runner]

I found this, took it off the side of a recharge can for future reference.

 

[ecally]

I charged mine to 35 on the low side and it has been working great all summer. Mine was down around 24 before that. Also cleared up the sight glass with compressor on, and foams when compressor is off.

 

[won4run]

Thanks for the replies so far. I looked at the sight gauge and it is clear while running, but doesn't seem to foam up at all when you turn the compressor off. From the manual, it says that it could be possibly overcharged when this occurs. However, looking at the pressures and from your suggestions it looks like I might be undercharged. Attached is a picture of the manual page with the star where I measured. (.17 MPa low side and 1.4 Mpa High side) Any ideas on how to interpret the manual where it shows the blower Hi zone and blower LO zone? It was definitely on HI when I was checking the pressures.

 

[81runner]

.17 mpa=24.656 psi. That's low for low side pressure at the ambient temperature given when measured.

 

[won4run]

I rented some gauges and checked pressures again.

Temperature is about 95 F outside.

Engine off pressures are 65 psi LO and 175 psi HI.
Engine on compressor off is 85 psi LO and 125 psi HI
Engine at 1500 rpm & compressor On is 30 psi (0.2 Mpa) LO and 225 psi (1.5 MPa) HI

Per the book, the acceptable ranges are:
0.15 to .25 MPa on the LO
1.37 to 1.57 Mpa on the HI

I added about 6 oz of Freon and the LO side pressure stayed at 30 psi (.2MPa) but the HI side climbed to 275 psi (1.9 Mpa). I didn't want to risk overcharging by adding more freon because it seems it is slightly overcharged as is. However, the graph in the manual shows two sections for pressures based upon blower setting.

There was no effect in vent temperature when I added Freon. I got around 60 F vent temps with blower on max and all doors open. There's a lot of water coming out of the condensate line for whatever that's worth.

What am I missing? I'm about to break down and take it in somewhere if I can't get it figured out. Also, I pulled the cabin air filter out completely.

 

[AuSeeker]

It's possible that the blend door/s are not fucntioning correctly, if the door is directing some of the air through the heater core and the AC evaporator at the same time then you will not get cold AC.

That being said, the cabin air temperature sensor which is located just below the ignition switch, look for the little slots in the plastic trim panel, the sensor is on the backside of the panel, could be dirty or bad or going bad, which could make the above mentioned senario a possiblity, also blend door servo could also cause it.

 

[JRZEE2000TR4LTD]

I rented some gauges and checked pressures again.

Temperature is about 95 F outside.

Engine off pressures are 65 psi LO and 175 psi HI.
Engine on compressor off is 85 psi LO and 125 psi HI
Engine at 1500 rpm & compressor On is 30 psi (0.2 Mpa) LO and 225 psi (1.5 MPa) HI

Per the book, the acceptable ranges are:
0.15 to .25 MPa on the LO
1.37 to 1.57 Mpa on the HI

I added about 6 oz of Freon and the LO side pressure stayed at 30 psi (.2MPa) but the HI side climbed to 275 psi (1.9 Mpa). I didn't want to risk overcharging by adding more freon because it seems it is slightly overcharged as is. However, the graph in the manual shows two sections for pressures based upon blower setting.

There was no effect in vent temperature when I added Freon. I got around 60 F vent temps with blower on max and all doors open. There's a lot of water coming out of the condensate line for whatever that's worth.

What am I missing? I'm about to break down and take it in somewhere if I can't get it figured out. Also, I pulled the cabin air filter out completely.

Your pressures should be THE SAME when the compressor is not running. You said the LOW side pressure is 65-85 psi and HI side is 125-175. Really engine on or off should matter, the pressures should be the same on the suction and discharge sides, so maybe your gauges are reading wrong or the pressures are in flux because of a restriction. When the compressor comes on your low side should go down around 30-45 psi depending on ambient temp and 190- 250 on the HI side. Looks to me like you have an obstruction, probably in the expansion valve.

PS I'm also confused about the fact that you have condensate running out of the evaporator. That can only happen if it's cold. So maybe you also have a blend door issue or heater valve issue. Recheck those pressures because somethings not right with your readings. Use one hose and hook it to LOW side of your truck to the High port on your gauge set and then switch it to the low port and verify you get the same readings. Make sure the valves are CLOSED.

 

[won4run]

Thanks for the advice. I also thought it was odd that they didn't read the same pressure. This is a different set of gauges from the first set I rented, so I'll recheck everything tomorrow. How difficult is the blend door actuator to get to and how would I go about checking the heater valve?

 

[AuSeeker]

I just looked at your first post and see you have the dual climate control which means you have 2 blends doors, one for each side, if you're getting the same temperature air out of both sides and both sides are set the same then I wouldn't think you are having any problems with the blend doors actuators, the blend doors control how much air goes through the AC evaporator and or heater core to control the temperature in the cabin per the settings on the control panel, if the cabin has reach the settings on the control panel then you will get more air through the heater core or evaporator or both depending on what temperature air is needed to maintain or reach the settings, if the cabin temperature sensor is dirty or defective the control panel doesn't know the actual cabin temperature, this could be your problem, just unplug the sensor and then remove it and clean it if it appears to be dirty and see if it solves the problem.

There is no "heater valve" per se.

 

[won4run]

I'll check the cabin temp sensor also, I think you're right that this could be a likely cause. Should this show up in the diagnostic mode test? From everything I can tell with the gauges, the system appears to be cooling as it should, I'm just baffled why it isn't translating to cold air. Is there a way to "manually override" the blend doors? Air temp for each side is the same when not using dual mode. I'll try the dual mode to see if the temp adjusts independently.