Hello everybody, first off I'll start by giving a little history. My 05 has always had good air conditioning front and back but around three weeks ago it quit blowing cold. I found all the 134 had leaked out through a pin hole in the aluminum line that runs down the back of the engine to the rear ac unit. I removed the line and brazed the pin hole. So I reinstalled the line, put a vacume on the system for 20 mins then let it sit for another 20 to make sure I had no leaks. All seemed good so I re charged the system. Now my front blows nice and cold but the rear is warm? My pressures at idle are around 40psi low side and 200ish on the high side when the engine is warmed up and the ambeint temp is around 74 f. If I turn it to the warmest setting for the rear it gets noticeably hotter so I'm thinking the blend door is working properly?? I've read that the thermal expansion valves can give some trouble so I pulled the jack and cubby out to gain access to it. I tried tapping on it with no gains. Also the top left line seems to be pretty cold coming out of it too the evaporator but the line coming out of the evap is room temp. I was very careful not to let any junk get into the lines when they were apart for the line repair but I'm thinking maybe some junk has plugged up the TXV? Any feedback or opinions on this would be greatly appreciated. Thanks.

 

How many ounces of refrigerant did you put in the system and how accurate was your measurement?

 

Hmm well it's funny you ask. Lol. I have a bulk can of 134a and a not so accurate weigh scale. By my scale it started to blow cool after about 2 1/2lbs. So I know the system holds 4 and a bit, so I kept adding and ended up putting around 3 1/2 lbs give or take because my scale is a pos. Could this be part of my problem? I didn't want to overcharge the system.

 

I had a similar situation as yours where the rear AC wasn't cold, but front was cold. In the cubby, the AC line was cold, too. Replaced the thermo expansion valve in the back and was good afterwards.

 

IIRC, the specified amount is 58 oz (3 lb, 10 oz) <Edit: 68 oz 4 lb, 4 oz. Danged memory....>. If the system is undercharged by even a few ounces, the rear AC won't work properly while the front is okay.
If it worked correctly before the leak, I'd be looking at adding an ounce or two at a time and checking operation if you are unable to accurately meter in the charge.

Sure, it might be the TVX valve, but, given the ambiguity of how much refrigerant was added, it's impossible to do more than offer educated guesses.

 

That's right about what should be in there.

 

You have done pretty good troubleshooting. Really does sound like stuck or plugged TXV in the rear.

 

Thanks everybody for the feedback. The sticker under the hood says it holds 4.25 lbs of R-134. So maybe I'll add a little here and there and see if it helps but not much else I can do other than try a valve. Oh well at least the fronts working for the weekend. Thanks again.

 

Just a heads up to anybody else having trouble with there rear AC, I replaced the TXV valve and it's working really good now. If your doing this do yourself a favour and replace the orfice tube at the same time. Mine was at least 50% plugged off and others have found the same. My excursion has around 225 000kms on it just FYI.