A/C overcharged

[AuburnFJsexy]

I bought my 80 last Oct. and the guy I bought it from said the ac doesn't work, so I figured I would look at it later. Well it is starting to get hot here so i tooka look at why it might not be working and noticed the ac belt was pretty worn out and loose so I replaced it thinking that might be the problem. After changing the belts (changed the other onces since I was in there) I cranked it up and it smelt like something was burning, so i checked the belt and it was tight. Tried the AC and it was a a little cooler than without it (unless i was just hoping it was), but definitely not working right. So I went and got a recharge bottle with a gauge on it and attached it to the low side, and it shot straight to the red and was reading about 90 psi. I am thinking the PO tried to recharge the AC before and overcharged it and figured something else was wrong with it and left it be. This is my first real time to work with an AC unit, so I am lost in the dark. Any advice would be great...

 

[john_eckels]

I am not an A/C expert but the low side at 90 psi is not a good sign. The High pressure reading is what you should be using to determine the charge level. It should be about 2.5 X the ambient temperature. You will need a set of manifold gauges to read the high side. I picked up a set at Harbor Freight for around $40 on sale. For a quick check, you can use the sight glass which is located on the drivers side towards the front under the lip of the fender. When the A/C is running, the glass should be clear without bubbles. When the compressor turns off, you should see bubbles immediately. If it takes a while for the bubbles to show, it is most likely overcharded.

 

[AuburnFJsexy]

I know 90 psi is REALLY HIGH for the low side, that is why I am wondering what is going on in the AC. The recharge bottle I purchased said to attach it to the low pressure side while the AC is on high. Through some searches I have made, I read that the bubbles behind the glass is not an accurate way to to tell the charge with R134a. Is this correct? If the system is overcharged, how do you get it down since you cant release it into the atmosphere?

 

[jlg32281]

You can release it wherever you want, screw Al Gore!

 

[canman]

I worked most of my professional career as an engineer designing HVAC systems special purposes vehs (military/ construction/ forestry/ mass transit) so I will try to provide some advice/ comments, but it's been a while since I have worked in this field, and I am not an AC mechanic. I also don't know the specifics of the 80 series AC system including wiring schemtics, but here I go.
1. Not to sound like an A-hole, but AC systems require special knowledge and tools (expensive) to diagnose and repair and are not something people typically try to tackle, and when they do, they usually end up doing more harm than good. It was my understanding that it was illegal to try to recharge an automobile AC system without having first identified and then repaired the leak. I still do not know why such products are allowed to be sold when the avg person cannot possibly do this. Perhaps other could comment on this.
2. There are a few simple things you can check like making sure the clutch enages when the AC button is pressed. If it does not engage, it could mean one of two things (typically). You either have a low refrigerant charge (or none) in the system, assuming it is not below 40F outside, or there is a problem in the wiring/ AC button/ refrigerant pressure switches. You can check to see if you are getting +12V at the compressor, and if you are then there is some refrigerant in the system, which then means there is a problem with either the clutch or clutch coil. Typically there are two refrigerant pressure switches wired in series with the compressor clutch coil. A low pressure switch and a high pressure switch. These switches can be individual switches or combined into one "binary" switch. Again, I have no idea what type is on the 80 series LC. The low pressure switch will normally be closed and opens at 15 - 25? psi. The high pressure is also normally closed, and opens around 280-300? psi. The purpose of the low pressure switch is to prevent operation of the AC compressor at low ambient (outside) tempertures (usually less than 32F) to prevent freezing of the evaporator coil, and when there is a low refrigerant charge in the system. The high pressure switch is obviously there to protect the compressor from excessive pressure due to a blockage in the refrigerant circuit, or excessive pressure due to regrigerant overcharge or poor condenser cooling performance caused by poor airflow due to blockage of the condenset coil or no condeser fan operation (not applicable here).
3. In your case it seems that you tried to add refigerant to the lowside (low pressure) fitting and were unable to do so due to higher pressure in the system. Are you sure it was the low side fitting, and if so was the compressor clutch enaged? The reason I ask is that if you tried to add refrigerant to the highside fitting, it will likely not go in. Also, if the compressor clutch was not engaged, then the refrigerant pressure in the system would have been the same between the "low" and "high" sides which typically is similar to ambient temperature. For example if it is 90F outside, the refrigerant pressure would be approx. 90 psi and it would be unlikley that any refrigerant would go in.
4. Again without having the proper tools like a set of refrigerant gages etc, it will be almost impossible to diagnose or repair the problem. My advice would be to take it to a reputable AC shop. Hope this was of some help. Good Luck!

 

[RedTacoma]

I know 90 psi is REALLY HIGH for the low side, that is why I am wondering what is going on in the AC. The recharge bottle I purchased said to attach it to the low pressure side while the AC is on high. Through some searches I have made, I read that the bubbles behind the glass is not an accurate way to to tell the charge with R134a. Is this correct? If the system is overcharged, how do you get it down since you cant release it into the atmosphere?

If it is 134a then you can release some of it to the air no biggie just don't breath any gas, that thing will give you instant hearth attack.
Release little and see if AC starts cooling. Sometimes people forget that too much gas is no good for AC. Everything turns to liquid and you get no cooling.
Honestly, I never do check the pressure and always filled by adding some and measuring temp. Always works for me you get max cooling with out overfilling AC.

 

[TX Cruiser]

If the compressor is not engaging, then 90PSI on the low side could be perfectly acceptable. The pressures will equalize once the system has been shut down, eventually. The low side will come down when the compressor is turned on. Low side=suction side. If the compressor is engaging and the low side isn't coming down, then the compressor might be shot, or there is too much freon in the system.

Check your fuse, it may have popped which will not allow the electro-magnetic clutch to engage the compressor. It happened to mine for no appearant reason. If it pops again, the clutch or something else is shorting out.

You may also have bad expansion valve that is stuck wide open, or a bad pressure switch. I need more info to help you diagnose this problem. A set of gauges would be nice, but not necessary. What is the compressor doing? Or not doing? What does the gauge say when when it is turned on?

When charging with DIY cans and hoses, about the maximum that you are going to get into an empty system prior to engaging the compressor is one 12 oz. can, maybe 1 1/2 cans. It's really when the pressure in the system equals that of the can, but anyway. The rest will get sucked in when the system is turned on.

 

[Rocket Man]

I agree with TX Cruiser. When your AC Compressor is not turning, or has just started to turn, both sides of the system will have similar pressure... 90 psig, is nothing to get excited about. Check to make sure the clutch on the front of the compressor is engaging... watch the compressor and make sure it's turning while the motor is running. Many times you can actually hear the click when it engages.

The glass indicator is actually a very good way to determine what's going on with your AC system. A gage set will tell you if you have any sticky, or leaky valves on your compressor and can tell you if you have a restrictive TXV... not to many people do unless you have fried the AC compressor and metal shavings have been circulated through the system.... again most folks don't.

Lastly don't get too wrapped up in discharging R134a into the atmosphere... the "older" freon, R12, however should not be vented out. It needs to be reclaimed.

Hope this helps.

 

[AuburnFJsexy]

thanks for all the replies, I know the clutch is engaging, because I can see it spinning on the front end of the compressor. I know that it is engaging, but i do not know if it is working properly. I did release a little of the 134 out of the system, but only for a couple seconds, would it take a long time to release enough pressure out of the system to get down to "normal"? I will also check the glass indicator and see what it is showing. I might end up taking the truck to a shop down the road from my house next week if I cant figure this out this weekend.

 

[TX Cruiser]

We need to know what the high side is reading, and may need you to test the compressor. Testing will require you to unbolt the hoses at the compressor and using your fingers to check for suction and discharge. To do that you will have to accept that you will loose all the freon in the system and will have jumper the low pressure switch, but we will cross that road when you are ready.

It'll take awhile to release enough to get it down, maybe 15-20 seconds, but check the sight glass while the compressor is on to see if freon is moving first.

I'm guessing that the compressor is toast, but it could be a bad expansion valve that is stuck wide open. Can you borrow a set of gauges?

 

[onewhippedpuppy]

We need to know what the high side is reading, and may need you to test the compressor. Testing will require you to unbolt the hoses at the compressor and using your fingers to check for suction and discharge. To do that you will have to accept that you will loose all the freon in the system and will have jumper the low pressure switch, but we will cross that road when you are ready.

Doing this guarantees that he will either have to take his truck to a shop or purchase a vacuum pump. After opening your system to the atmosphere you must vacuum it down prior to re-charging.

Auburn, did your gauge shoot into the red WHILE you were charging? Note that it will max out while you are discharging the refrigerant. You have to let off of the button and allow the system to level out prior to reading the gauge. Also, the gauges on the cheap sets aren't the most accurate.

If your system blows cool, your compressor engages, and you have bubbles in your sightglass, it's worth trying to charge it (within reason). If you don't see any improvement you're really beyond DIY territory without a set of gauges.

 

[TX Cruiser]

Matt, Matt, Matt. This is shade tree for the time being. However, you are right, vacuuming the system down will help in aiding you to blow popsicles from the vents. It also removes moisture from the system, but it will cool fairly well with out that step of the process. We aren't to that stage though.

Is the wifey still driving the Cruiser or did you get it back?

 

[Rocket Man]

Hey guys one more thing I wanted to add. I know it's kinda redneckish... but I have been able to get good results using a modified vacuum line hooked up between the low side of the system and a good engine vacuum source. Like I said it's probably not as good as using a good quality vacuum pump, but it's free and it works good enough to suck any water vapors out.

I used an old gage set I had, cut off one of the lines, spliced it to a piece of vacuum line and fired up the engine and let it idle. Pulled a vacuum for a good 20-30 minutes shut the valves, turned off the motor and let it set for a couple of hours. Once I was happy I had a good tight system. I charged it up using the over the counter DIY setup.

Hope this helps out, without being too confusing.

 

[TX Cruiser]

That's good stuff right there!

 

[john_eckels]

Through some searches I have made, I read that the bubbles behind the glass is not an accurate way to to tell the charge with R134a. Is this correct? If the system is overcharged

It has worked pretty well for me and is documented in the FSM for the LX450

 

[The Abbot]

I bought a CBOA recharge kit today, assuming the problem with my AC was lack of refrigerant. Followed directions on the can, it was filling up nicely until about halfway through the can I hear the belt screaming as it struggled to travel around a stationary compressor pulley.

I let go of the button on the refrigerant, the compressor pulley began turning normally, and voila- my AC is now working VERY well. Throughout the rest of the day, it would occasionally "chirp" for a fraction of a second intermittently but is still holding a charge.

Maybe the belt is just old, maybe the compressor/clutch is going bad...hey, it works though.

I'm going to replace all three belts this weekend, but have no interest whatsoever in messing with the AC system any further until the is no longer happy with the temperature of the air coming out of the vents.

 

[dodgefate]

when you hook up the gage to the low side the pressure shoudl be close to how hot it is outside...... When the compressor is running it shoud drop betweeen 30-60 lbs. if it does not drop that means that the compressor is week. If the pressure goes up there could be a block. if it drops below 30 start adding some freon. If it is still not working check the fan clutch, with the car off see if it wobbles from side to side its no good. check that the clutch is coming on, if not check the wire going to the compressor for power when the button is on...... let me know what you find.