Automotive Air Conditioning Information Forum

This van has an add on dual conversion for rear AC Rear unit uses an exp valve It has the underside condensor on drivers side under the van. Front AC is not blowing cold. Looking for expansion valve or orifice tube but cannot fins anything. What system might this be using? Thanks Dave

Why do you suspect expansion valve- ? when the number one cause of automotive a/c failure is loss of refrigerant due to a leak? Check your refrigerant charge by having it extracted and weighed and compared to factory labeled amount for your system. That is always the first diagnostic step. You cannot determine refrigerant amount by pressures.

GM Tech wrote:Check your refrigerant charge by having it extracted and weighed and compared to factory labeled amount for your system. That is always the first diagnostic step. You cannot determine refrigerant amount by pressures.

There may be trouble trying to find the listing for oz. refrigerant with an add-on system...can you provide that to him?

First thing we did was extract and evacuate system and recharge. This is a school van and has a label for the charge amount which is 4 lb 134A. Rear unit is blowing 50 degree air at 91 degrees here in nj front is blowing lukewarm air 70 degree. System still has GM accumulator on it which is cool but not cold like our other similar vans.

If it has an accumulator that means it was originally a simple orifice tube system. Somewhere between the tee in the liquid line and the front evaporator there must be an OT. Factory dual systems were commonly OT in the front and TXV for the rear.

That is what I thought but cannot find one anywhere. I have pulled the connections that are there apart looking for a pocket for an orifice tube but none are there. In this instance the take the connections apart and install Tees into the line and run to the back unit. I opened up the rear and there is a txv in that line.

Do you know much history on this project? Has the front ever worked the way it was when you got started working on it? The reason I ask is "maybe" the oriface tube is just not there and that is the problem. Just thinking, but maybe someone thought it was just a filter and did not put one back in at some point.

I've seen two orifice tubes in similar units, and also have seen no orifice tube in front- it was missing- put one in, in the proper location and all was fine. Look for the OT dimples at a connection behind the tee-- also look for an OT in condenser outlet connection- there should NOT be one there....see n it both ways from unadvised mechanics....

GM Tech wrote:... and also have seen no orifice tube in front- it was missing- put one in, in the proper location and all was fine. ....

WOW I had about the same idea as GM Tech, I must be learning something here!

I have been up one side of this one and down the other no dimples or a place to fit one in the piping. I think someone in its past, we bought this used from another bus company, eliminated or cut out the tube. It is a very poor and cheap aftermarket conversion with all homemade lines. Our Napa has the old style replacement orifice tube assembly which has a compression fitting on one side and threaded line connection on the other. Will I hurt anything installing it in the inlet to the evaporator do you think to test it out?