2003 Jeep TJ - what's wrong with my A/C

[Freshly Minted Georgian!]

New to component diagnosis of A/C so I need advice. I'm working on a 2003 TJ Sport, 4.0L engine. When I hook up gauges to both sides here is the behavior I get.

• A/C does not blow cold
• Low side showed about 20psi, high side about 40
• Compressor clutch was not engaging
• Added some 134a to low, brought pressure up to around 45psi at which time compressor clutch would also engage and the compressor would cycle on/off
• Slowly added more refrigerant, between cycling that would bring the low side up to around 50psi. When compressor cycled on high side would spike up to 125psi, low side would drop to about 30psi.
• When compressor cycled off the pressure would drop within a second or two back down to around 40, about the same as the low side.

My theory.....expansion valve problem and probably also a significant leak. I was thinking of replacing the expansion valve, orifice tube and condenser, plus any orings inferred by replacement of those things. Am I way off base here? I do also have a vacuum pump but have not yet attempted to purge out the lines and see if it will hold vacuum. From the pressure behavior I assume the answer is no, its got a leak somewhere. I also have a UV flashlight. What else should I try? Need to get the A/C solid, my daughter has health problems and is very heat sensitive so until I get this repaired she can't go jeeping with me.

 

[Shey]

Your still low on Freon, high side should be above 250 in 80-90 deg weather. Google 134A pressure chart, it will show you standard pressures for ambient temp ranges. Sound like you have a good size leak, get yourself a sniffer, lots to be had at local pawn shops. Hope this helps.

 

[Freshly Minted Georgian!]

I know I'm low on freon, when the compressor cycles off the pressure drops like a rock, it's not building pressure up.

 

[rumrunner55]

shine a black light in the bay youll see the leak

 

[Billybob270]

As another member mentioned, you are about half-full on your freon. When the compressor cuts off it is because there is a low pressure switch on your low side. It varies from different car manufacturers but the low side has to maintain around 40~45 psi to keep the pressure switch closed. When you compressor cuts off, there isn't enough freon in the system to provide any back pressure and the 125psi on the high side immediately vacates to the low pressure side. That's why you see almost an instant pressure drop when the compressor cuts off.....this is normal. High side on a fully charged system on a 90 degrees day can be above 250 psi. As the other member mention, look online and get a pressure chart. If you overcharge the system you can damage the compressor.

 

[Freshly Minted Georgian!]

Pressure specs show 37-43 on the low side and 250-300 on the high side. I just couldn’t get enough refrigerant in it quickly enough to get the high side to stay stable. I’ll take my new uv light out there tonight and see if I can see any obvious leaks

 

[Freshly Minted Georgian!]

I have the service manual too, that’s where I found the pressure ranges

 

[Freshly Minted Georgian!]

I have an electronic copy of the full service manual, 1676 pages, for 2003 if anyone needs it, PM me. Just reading, looks like there isn't an expansion valve in this system.

 

[Billybob270]

Pressure specs show 37-43 on the low side and 250-300 on the high side. I just couldn’t get enough refrigerant in it quickly enough to get the high side to stay stable. I’ll take my new uv light out there tonight and see if I can see any obvious leaks

FYI - If you don't have dye in your system, you will not see a leak with an UV light. For trouble shooting a leak, AC shops will inject a florescent dye into the system. Then when it leaks out, you would be able to see the leak from the residue left.

 

[Freshly Minted Georgian!]

I have a bottle of oil with leak dye, haven’t put any in yet though