I am going to replace my O Tube and just want to confirm its location. I know it is in the line at the condenser but I am just not 100% clear if it is in the high or low pressure line (top or bottom line).

I have gone over the service manual, but I guess sine I am not up to speed on the terminology it is throwing me off.

Just looking for a nudge in the right direction.

 

It has to be in the high pressure line. The only one I've replaced was in an old van and it was located close to the firewall close to the evaporator, not condenser.

 

OK thanks!

Yeah this one is up at the front. The location in the service guide is

The evaporator core orifice is located inside of the condenser to evaporator line at the condenser outlet fitting

but at least an easy location to work from

 

When the AC is operating, is the high pressure line hot or cold? Downstream of the orifice, the line will be cold. Before the orifice, the line will be hot.

 

Downstream it is hot, my hand is too fat to get in to touch it upstream of the orifice without burning it on the upper rad hose.

The pressure readings seem to show there is some restriction, I also was having issues with the evap coil icing up with a proper charge.

 

When you post a question about your vehicle, always state what the vehicle is.

 

Oh my bad, its a 2004 F150 FX4 5.4L New body style.

 

Icing is usually caused by too little refrigerant or too much restriction at the orifice tube. I don't know if there is a filter in front of the orifice but there may be. My first auto ac repair was on a 74 Chevy bought from a gas station/used car dealer. The AC wasn't working and he said he knew it was the drier and gave me one and let me change it using his vacuum pump. That didn't fix it. This car had an expansion valve not an orifice. I found out there was a cone shaped screen in front of the variable expansion valve that you could not see when the joint was disconnected. I used a screw inserted into the line to grip it and pull it out. After cleaning the screen the system worked great.

 

Or by a compressor clutch that stays engaged instead of cycling (CCOT systems).

 

On this model, the orifice tube is the filter, I suppose some stuff might get caught in the dryer but the orifice is all screens.

Its a $3 part, so since it will be evac'd anyways for the recharge, might as well replace the tube at the same time.

 

Let me know what fixes it!

 

Well I replaced the tube, it was in (what I would call) the low pressure line, it was the same line as the low pressure fitting. It looked clean, just lots of oil in it. replaced it anyways, and recharged it. Runs good, vent temps are in the high 40's. Only problem I am having, and I don't know if it even is a problem, is that at higher RPMs like highway speeds the compressor starts to cycle on and off. The low side pressure drops until it cuts out around 20 PSI, then it recovers and runs again. Not sure if it is normal or not. I put 37 oz into the system.

 

Not normal.

 

Didn't think so. It acts like it is undercharged, but I put the amount in the service guide shows. My underhood tag is long worn off.

 

I suspect there is still a restriction in the line somewhere.