Hi guys. Another X300 in my house. So my son brought me his XJ6 in for various repairs. Sure, Dad's got your back. Went to charge the AC system and found there is a leak. I will need to investigate. New compressor, drier and condenser about 3 years ago. So I shot it with R134a 1/3 can and the low side shot up to 90 lbs and high side to 75. I am used to seeing about 40 on the low side and over 150 on the high. PS, both radiator fans blowing on high. Compressor clutch engaged. The protagonist is a 1995 XJ6. I bi passed the fan pressure switch as per technical bulletin. Before I blow anything up are these pressures normal?

Second, the center blower has minimal air flow. To remedy this I press defrost, then press the center vent position and it works much better. I suspect there is an issue with the air distribution system Any ideas?

I guess I will be buying a system dye kit with a UV lamp to find the leak. Hot days here in Alabama so any help would sure be appreciated.

 

So, I may have answered my own question. Sort of. I ran the AC self test and I got codes 23 and 24. 23 tells me refrigerant is low. 24 tells me face demand potentiometer fault. What is that? Any ideas? The plot thickens.

 

There is a self test on the A / C control panel that can give you some codes as a basis of covering the basis and can go from there

See page 110 of the Doc and the following video someone made

T703 BOOK (jagrepair.com)

Editing

 

In your quest to be a X300 problem solver the code 24 has nothing to do with freon charge so hang with me

 

On the center vent there is a knob from red to blue that is common to go bad and can be replaced by pulling out on the vent carefully and unclips but the louvers can break if pulling from the center venter of the fins

The pot gets 5.0 reference volts and is modified from there

This was deleted on the pretty much the same on the later X 308 model

Pic coming soon

 

Get new GM style ball valves, old ones always leak after being disturbed. Easy job, the valves screw right on to the pipe fittings. Of course the system must be empty to replace them.

It could take a little time for the system to pull in the 134, especially if it goes in too fast. Over time (perhaps 20 minutes) the pressure will show up correctly, unless there is a blockage. Which is unlikely with a new drier bottle installed.

 

 

Blockage is another issue that can be easily resolved with a suggestion from Motercarman ( Bob ) with his experience but requires a freon charge and expense

The center vent check is free and in my opinion if resolved would be first before the exspence of a freon charge

 

I would purchase and add some UV dye to the system. They sell these specific for AC systems.

I would then charge up the system. There will need to be a minimum charge before the compressor agrees to kick in and start doing its job. I think Code 24 might be telling you this.

Do NOT add any refrigerant with leak sealer, or any other type of conditioners. Just straight up r134a.

After awhile check, with a blacklight, for signs of that UV dye.

BTW, one of the key components you should replace when the system is discharged, is the expansion valve. It could be blocked up, or just failed. It's not expensive, but I don't know exactly where that is located on the x300.

 

Thanks guys. The UV dye seems to be the way to go. I think there is a bad leak somewhere. Maybe a stone hit the condenser. Also, I would like to address the center potentiometer. Is there a way to disconnect it without taking half the dashboard apart? While I am in there I will fix the vanes in the vent that broke. There is a plastic bar that moves them all at once. Those always brake. I am having a bunch made with a 3D printer.

 

The center pot has a big effect on the cooling output and should just pull off as the whole center vent grill from the cabin side to you

You can practice with one at a salvage yard

The location of the TXP valve on the X300 is sandwiched between the rear firewall and the evaporator inside the cabin so to touch it is a lot of work but there is a way to free it up flow wise without touching it

You can do the easy things first like clean the cabin temp sensor of lint which does not show up as a code

Clean the sensor fan with air and a brush only

This is located below and to the left of the steering column as a 1 inch square vent louvers.

 

Stick the dye in, and have a look. Very bottom edge of the condenser at the mounting points a popular spot. You mentioned a new condenser 3 years ago, but if second hand or the mounting bushes weren’t replaced, quite possible it has gone there. The dye would be a good check. If there are no leaks you are going to lose what is left of your gas charge as you tackle the compressor….

 

Ive been busy tackling other issues on the car, but back to the AC. Sleekjag12, what are the GM ball valves and where do I get them. I took out the center vent and tested the potentiometer with an Ohm meter and it works just fine. I suspect that the leak may be in the schrader valves.

 

The center pot reports to the climate control ECM to move a specific trim / blend door that can be driven manually with a 9 volt battery without the ECM and frozen in position for the season

Pic coming

You center vent pot code may just cover the pot or the trim motor also

The trim motors have a position sensor in each that come to agreement to what it is commanded and the motor can be fine just no position sensor to say it's OK

You can get to the trim motor connector without going deep into the dash

 

"Brit"carnut (lol) those valves should be available at any auto parts place. I hope. They are not Schraeders, they don't have the pin, and they are not sold as "cores". This photo is them exactly, but I just pulled it off a search. Ironically most results show the Schraeder pins, but I don't know of any of the correct Jag/GM fit that have a Schraeder pin core, only the "ball" style core that is not replaceable.


Notice the slight "flats" on them that allow you to carefully unscrew them from the pipes.

 

We used the term Schraeder in aviation when there was a hex nut you twisted to open then twist back shut

These can be found on motocross motorcycle shocks

So using Schraeder as a search other the ball check valve may lead you astray.

I'm going through this on a New Beetle A / C servicing port getting past the newer freon can design

 

So, Sleekjag12 was right. I removed these from the car and will be ordering a set this weekend. I hope this will solve the leak. we shall see. I found the brake leak which turned out to be a punctured brake hardline. I also repaired the center vent that had broken slats. Like new! You guys are a great help. Without the like of you I couldn't keep this car.