Howdy guys, I've got a 97 SE with the auto climate control and some A/C problems.

On a hot day my A/C doesn't get very cold at all and I've ruled out the auto climate control system because it is capable of blowing cold air when things cool off at night, etc.

Here are my observations:

1.) only slightly cool air on a hot day.

2.) the A/C compressor runs continuously, never clicks on or off.

3.) The high pressure line going out from the compressor to in front of the radiator does get hot. Not burn your finger hot, but it gets hot.

4.) The high pressure line going from this to inside the cabin is cooled off to ambient temp fine (the rad fans are running)

5.) the low pressure line returning from the cabin remains luke warm. This should usually be cold I would assume? It gets ice cold in every other car I know.

6.) For some odd reason my cheap A/C refill can gauge will sometimes read in excess of 60psi on the low pressure line with the compressor running and in excess of 80psi with the compressor off. Most of the time with it running it will read about 40psi.




I've tried letting some pressure out because I feel like the system might be overcharged, but that doesn't seem to affect the reading on the gauge much at all, nor has it improved or worsened the cooling.

Do any of these symptoms sound like the system is over or undercharged? I just find it odd that the compressor runs 100 percent of the time and the low pressure line doesn't get cold. In fact, sometimes it is the same temp as the line going from the rad to the passenger compartment.

 

Did you do an evacuation and replace the drier prior to the recharge? Chances are there's humidity in your system as well as air which is what contains the humidity.

Your compressor clutch should definitely engage and disengage once temp is reached. My 3rd gen has a similar problem where the compressor is always running and causing the lines to freeze and it will not blow air until they thaw...

 

Nope, I actually haven't done a recharge, I just had one of those kits lying around from another car and used the gauge on it. And I definitely don't have any line freezing problems thats for sure. I don't think a single part of this A/C system gets anywhere near freezing temps.

What is this drier you speak of that would need to be replaced? I'm thinking about seeing if I can evacuate the whole system and start from scratch.

And thanks for the help so far man!

 

If the system hasn't been open for any lenghts of time the dryer is fine.

The ONLY way to correctly charge an R134 system is by weight while the system in under a vacuum state.

Take it to a shop that has the proper equipment to do this. They can also troubleshoot it better by looking at both the high and low PSI while the machine is attached to the system.

FWIW - I'm not sure when Nissan changed the system, but on later 4th gens (my 99) the Calsonic compressor does not cycle.

EDIT: Make sure your evaporator is clear of any debris and BOTH cooling fans are running when the compressor is on.

 

Sweet, thanks for the info. I think mine must have the newer system, looking at auto parts online it looks like the compressors for 97-99's are different than 95-96's. How do they keep it from freezing up if the compressor never shuts off?


Also, yup, both cooling fans run, the condenser (the thing in front of the radiator is the condenser right?) is clear.



Also, the sticker is no longer on my car, could someone take a look at theirs and let me know how much refrigerant by weight and lubricant to add to the system?

Thanks a bunch!

 

PER FSM
R134A 1,43 LBS +OR - 0,11 (23 +/- 2 OZS)
OIL 200ml (6,8 OZ) Nissan ac oil type S (PAG46 equivalent)

An aside...Unless a component has been replaced you shouldn't need more oil. Removing R134a from the system will have a negligeable effect on the quantity of oil in the system.

 

THERMAL EXPANSION VALVE
Another common refrigerant regulator is the thermal expansion valve, or TXV. Commonly used on import and aftermarket systems. This type of valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type. This type of valve is usually located at the firewall, between the evaporator inlet and outlet tubes and the liquid and suction lines. These types of valves, although efficient, have some disadvantages over orifice tube systems. Like orifice tubes these valves can become clogged with debris, but also have small moving parts that may stick and malfunction due to corrosion