How do you know if your A/C compressor is shot?

[MattS]

How do you tell if your compressor is shot or if you just have a leak? I know, put dye in the lines and so forth, but no leaks are found when this is done. I'm thinking if I pull the dash out and look in the box with the coil, that will be where the leak is, if there is one. I hope that makes sense... I am just wondering if there is a tell all sign that the comp. is bad.

Thanks in advance

 

[winterbeater]

Look at the drain from the HVAC housing for dye. It comes out through the firewall towards the right of the vehicle. You really don't want to pull all that apart to look for a leak. The usual place for a leak is at the compressor shaft seal. The leaks can be a PITA to find. Assuming that your AC doesn't work, have your tried putting a bottle of refrigerant in it? The best way to tell if you have a leak or not is to pull a vacuum, and see how long it holds. Without equipment, though, I'd try putting in a bottle of refrigerant and see if it starts to get colder. If it does, put in one more. Usually, you have to jump the low pressure switch on the accumulator bottle to get the compressor to pull in the refrigerant.

 

[MattS]

Here are the symptoms: It blows, kind of cold, when the outside temp is in the 70's or at the most 80. After that, it will smell like there is moisture in the vents and quit blowing cold until I turn it off for a while. It's like it is freezing up, but there is no ice anywhere that I can see. That's why I'm thinking either the compressor is on it's last leg or the leak is behind the dash.

 

[cashless]

is my compressor shot if it blew green/yellow oil and makes noise???

 

[winterbeater]

Blowing cold for a while, then not, is a sign of evaporator freeze-up. The evaporator inside the HVAC box under the dash gets so cold that it freezes up the moisture that condenses on the evaporator coil. Basically, it then becomes a block of ice and won't allow air to flow through. High humidity weather conditions, only running the fan at low speeds, and running AC with windows open, encourage this to happen. Air flow through your vents will be reduced if you have freeze-up. When the AC is turned off for a while, the ice block melts and the AC can work again. Some AC systems respond well to evacuating the system completely and carefully refilling the proper WEIGHT of refridgerant.

From your description, though, your air isn't really that cold, even just a couple of minutes after you start it. You have a good possibility of just being a little low on refridgerant from a slow leak, which is how I would approach it. You could try adding a can of refridgerant to see if it gets colder. Often this works fine.

 

[MattS]

winterbeater: You are right on the money. It isn't that cold to begin with. I will put a can of 134a in, but I know it won't last long. I have had the evap replaced before under warranty, and it helped for a while. My guess is the evap is bad again or leaking because I can not see the dye, or the compressor is messed up. For what it's worth, my heat barely works as well. I may just take the doors off and use natural a/c.

 

[winterbeater]

If evap is leaking, dye should come out of HVAC case drain at firewall. Could your blend door (temp control) be broken? Supposedly, that is a fairly common problem too. I have a leak in my system too, that I haven't tracked down yet. XJ's are also known for the evaporator rotting out.

 

[Ivan]

Still could be the ice build up as mentioned. Check the foloowing thread for what to look for and how to possible fix the problem...

http://www.naxja.org/forum/showthread.php?t=995209

 

[MattS]

Yeah, I read the TSB about the low pressure switch. I've replaced it multiple times to try to remedy this.

 

[winterbeater]

But if it's ice build up, it will blow very cold until air flow slows down due to blockage of evap with ice. Your system is just weak. Put a thermometer in the vent. Water won't freeze above 32. So at the vents, you would need to be getting at least 40 or 45 to lead to freeze up. Units I have seen that show freeze up also show extreme condensation on the outside of the HVAC box.