AC Problem

[toy4x4]

Ok Yeah I know... another ac issue... My AC is not cooling good when it's hot out Takes 20+minutes of driving before it starts to cool down inside even with rear ac and recirculate on. Weird thing is it blows warmer on driver side vents than passenger and rear (I have the 3 zone setup). I've checked and both my front blend doors seem to work fine... (I can visually see the shaft turn back forth a full 90 deg angle and no clicking heard) I have checked with temp gun and my side is always 10 degrees higher than other vents even when it's cool out and the ac is cooling ok.

 

[imp]

Ok Yeah I know... another ac issue... My AC is not cooling good when it's hot out Takes 20+minutes of driving before it starts to cool down inside even with rear ac and recirculate on. Weird thing is it blows warmer on driver side vents than passenger and rear (I have the 3 zone setup). I've checked and both my front blend doors seem to work fine... (I can visually see the shaft turn back forth a full 90 deg angle and no clicking heard) I have checked with temp gun and my side is always 10 degrees higher than other vents even when it's cool out and the ac is cooling ok.

How many miles on the A/C compressor? Driven in a predominantly hot geographical area, A/C on most of the time? System ever been serviced? Got enough juice in it? Compressors also wear out, losing volumetric efficiency. imp

 

[toy4x4]

I'm assuming it's the stock compressor and truck just hit 200K miles... I doubt it's been serviced... My initial thought was it's running a little low on the refrigerant but the compressor runs constant (doesn't do the on-off cycling like you see when they're low) I didn't own it last summer so I don't know how it performed previously. I thought maybe the vent blowing warmer on my side was a indicator of something? Also the low pressure return side at the firewall does not get cold and is usually warm to the touch.- Best I can tell this is where my vents are picking up the heat making them warmer than the passenger side. I'm thinking that my half of the evaporator coil is not getting as cold as the first half (passenger side) if this makes sense?

 

[TechGuru]

Return line should be cold and sweating. Need to hook up gauges to high and low sides and see what is going on.

http://www.harborfreight.com/ac-r134a-manifold-gauge-set-62707.html

 

[imp]

I'm assuming it's the stock compressor and truck just hit 200K miles... I doubt it's been serviced... My initial thought was it's running a little low on the refrigerant but the compressor runs constant (doesn't do the on-off cycling like you see when they're low) I didn't own it last summer so I don't know how it performed previously. I thought maybe the vent blowing warmer on my side was a indicator of something? Also the low pressure return side at the firewall does not get cold and is usually warm to the touch.- Best I can tell this is where my vents are picking up the heat making them warmer than the passenger side. I'm thinking that my half of the evaporator coil is not getting as cold as the first half (passenger side) if this makes sense?

Your system does not run the compressor constantly, so you can't really judge by that. Evaporator core freeze-up is prevented by use of a thermostatic switch which interrupts running of the compressor when the core gets too cold. imp

 

[toy4x4]

Return line should be cold and sweating. Need to hook up gauges to high and low sides and see what is going on.

That's what I was thinking on the return/low pressure line it should be nice and cold. I have fixed it now. I will post details in a few.

 

[toy4x4]

Turns out it was low. I added a 18oz can of r134a and she cools great now and both sides blow same exact temp!

Now for the details: This might help others...
I didn't use a gauge set so sorry if this isn't scientific... I just hooked up the gauge that comes with the recharge can on low pressure side... I was going off the instructions and had the truck hot -running for about 20 minutes with AC blowing on high up front and in back and recirculate on. Of course It wasn't cooling very good and it was like 90F ambient temp on a humid day and the air blowing out was like 86 on my vent and 76 on other vent... I had 55psi but the temp chart on the can said not to go over 50psi and so I was thinking that I had an overcharged system and decided not to add anything... So I played around a bit and found that if I turned the fans down that the pressure on low side would come down a bit. So I decided to wait till the next day and check right away with the engine cold and the fans turned on low not high... When I checked the AC with the engine cold this time and at 85F ambient Temp it was about 35psi and slowly climbing... I think the engine being cold and the refrigerant being cold made a big difference here in the AC pressure. So I went ahead and added some refrigerant... Meantime I kept a close check on the vent temps and pressure. After adding about half a can the temps were getting close to matching and the air was blowing cooler(Note: I didn't have it on recirc this time either just so I could get a more accurate reading on temps to tell if the temps changed due to my adding refridgerant) Pressure was up to about 40psi... I added the rest of the can and temps on both vents matched and pressure ended up about 45psi with both front and rear fans on low... and then when I turned all fans on high the pressure maxed out at 50psi When I was done I was reading 54 deg F on both front vents with fans on Low and 60 deg F with fans on high engine hot and idling for about an hour by this point with ambient air temp 85degF and I had recirc turned off. Pretty good cooling if you ask me... And it will freeze you out on the road now.

So my conclusion was that I was low in refrigerant. And it is better to not let the system get too hot by running everything on max on a hot day with a hot engine... This seems to overheat the refrigerant when it's low and cause an increase in pressure which in turn makes one think the system is already fully charged .... I'm sure If I had the high pressure guage set I could have seen all this from the start... But for those of us without guage sets this might be of some help.