A/C troubles

V

vrtillman

Member
Joined
May 11, 2021
Messages
25
Location
Texas
Having some trouble with my AC. I know enough about these systems to do simple R&R and evacuate/fill refrigerant, but that's about it. I've got a 98 4.0 and so far here's what I know:

AC blows room temp air at max cold setting and max blower motor setting.
Dash controls/blower motor work.
Compressor works.
Heater core has been blocked off due to a leak (I live in Tx so I'll fix it eventually, but its not a priority right now).
Hooked up gauges, Low side reads ~25-60psi (comp kicks on around 60, shuts off around 25), High side reads 100-150psi.
There's some neon stuff around the low side connection, I'm assuming this is some kind of uv leak detection.
After I disconnected the high side from the gauges, there appeared to be some kind of oily substance coming out of the connection/schrader valve. It ppeared dark green on a paper towel. I'm assuming this is compressor oil?

Not sure where to go from here. Idk if freon is leaking out past either schrader valve and i don't want to just willy nilly add freon and over-fill/pressure the system because I know that's just as bad.

I'm going to try and evacuate the system and maybe change out the schrader valves and refill, but if anyone has any other ideas, feel free to let me know, I'm just kind of working off of basic/common knowledge here
 
Yeah, the neon stuff is dye that was added to the refrigerant at some point for the purpose of being able to identify a leak because otherwise the stuff is colorless.

Based on what you're describing it sounds like the compressor is constantly cycling on & off. A low charge can definitely cause that. If you aren't sure what the state of the charge is I'd recommend doing a complete evac to include vacuum, then recharging with the correct amount to see where you're at.

The schrader should also not be doing that. Changing out the schrader valves wouldn't hurt.

While you're at it have a real good look around the rest of the system for signs of a leak. Refrigerant oil is greasy, so it's attract dirt & other shit floating around. Look for dirty greasy spots around pipe unions/connections & look over the fins on the condenser for the same thing.
 
  • Like
Reactions: Ericict
Sounds like you have a basic understanding of the A/C system and it's operation.
The green substance is most definitely for leak detection and the link down below can be used to determine where the leaks are.
Your system is definitely low on refrigerant which is what causes the clutch on the compressor to cycle.
The schraeder valves can be changed out using a removal tool in the link below.
Evacuate the system, replace the schraeder valves, inspect the system for leaks using the flashlight and glasses.
Once you are confident you have the system leaks repaired draw the system under a vacuum of 29.9 inhg or <500 microns from both the suction and discharge sides (quicker system draw down) then isolate the manifold valves and watch for 30 minutes to ensure the vacuum does not decrease, then charge with 20 oz of R-134a.
With the A/C controls OFF you can charge the system with the liquid refrigerant of one 12oz can with the can upside down and let sit for several minutes to ensure the liquid flashes off to a gas. Then turn the A/C system ON and charge the remaining 8 oz in gas state with can upright.
System pressures are indicated below for the ambient air temperature in your area.

r134a-low-pressure-chart.jpg


https://www.amazon.com/dp/B07F6H9KYG/?tag=wranglerorg-20
https://www.amazon.com/dp/B07HC9FNQY/?tag=wranglerorg-20
 
  • Like
Reactions: SkylinesSuck
If I were going to the trouble of replacing Schrader valves, O-rings, and evacuate the system, assuming the compressor and condenser are fine, I'd go ahead and replace the liquid line. The orifice tube is housed in the liquid line and can be plugged up, causing restrictions in pressure. It's a relatively cheap part, but I'd call Jeep air first to verify the fitment. I've installed a bunch of their parts and they are a great company to deal with.

https://jeepair.com/collections/ac-...-line-and-orifice-tube?variant=32066953969749
 
  • Like
Reactions: CharlesHS
Wow, thanks guys! I'll definitely look into the line replacement.

One question, with the system empty, could I use an air compressor to "blow out the lines" and check for any blockages or sludge? I'm assuming as long as I'm not blowing through the compressor that wont be an issue since I'm going to have to pull a vacuum once its all connected again anyway.

And would I need to add oil when i add refrigerant since the lines will be empty? I don't want to risk my compressor seizing up or anything.
 
Would not recommend blowing AIR thru the system; you will only add moisture to the lines and accumulator/drier.
The only type of air product you should use would be Nitrogen, but that is generally only available at an Air/Gas store or Welders Supply store.
The item recommended above is only used when you need to ensure there is no contaminated oil or contaminants in the system and a chemical flush is required.
 
That's what he was asking about though (I think). Cleaning out the system to ensure there aren't any blockages. Or maybe you are just saying don't use air? I feel like we are both talking circles around the same point lol.
 
  • Like
Reactions: CharlesHS
How much are you willing to spend? I've replaced two entire systems in the last three years and it was less than $500 for the parts. That included new compressor, condenser, accumulator/drier, and all the hoses. Do that and you won't have to worry about cleaning out the system, or its reliability. Given the vehicle is now 23+ years old, it's something to consider!

FWIW, this job is simple on your year, because the compressor is up top and easy to get to. This is not the case on later models.
 
  • Like
Reactions: SvtLdr
Irun said:
How much are you willing to spend? I've replaced two entire systems in the last three years and it was less than $500 for the parts. That included new compressor, condenser, accumulator/drier, and all the hoses. Do that and you won't have to worry about cleaning out the system, or its reliability. Given the vehicle is now 23+ years old, it's something to consider!

FWIW, this job is simple on your year, because the compressor is up top and easy to get to. This is not the case on later models.
Click to expand...
^^^This is good advice. It seems like nowadays, when dealing with older vehicles, it's just a better option to start over with completely new components.

Can I ask where you sourced your parts from? Have you had any experience with the brands that Rock Auto sells?
 
  • Like
Reactions: Irun
SvtLdr said:
^^^This is good advice. It seems like nowadays, when dealing with older vehicles, it's just a better option to start over with completely new components.

Can I ask where you sourced your parts from? Have you had any experience with the brands that Rock Auto sells?
Click to expand...
Best A/C source I've dealt with. I've installed multiple systems and parts from them. Great service and knowledge!

https://jeepair.com/
 
  • Like
Reactions: SvtLdr
Don't really want to spend a ton. I'm gong to see if change the liquid line and schrader valves makes a difference and work from there, but if I have to replace everything I will.
 
vrtillman said:
Don't really want to spend a ton. I'm gong to see if change the liquid line and schrader valves makes a difference and work from there, but if I have to replace everything I will.
Click to expand...
If you are opening the system then a filter/dryer and refrigerant oil will be necessary
 
Top Bottom
Back