Been getting warmer this past week, and noticed that the inside the cab was getting warmer as well. Have had the condenser get full of debris before, so tried that first. Spent 20 minutes blowing everything out, no change. Snapped gauges on, high side appeared to get a little high (around 275 psi), but low side looked ok for the most part (would come down to about 18-20 while compressor was running). Was expecting to see the low side lower, but went ahead and added some juice anyway. Added around 8 oz, low side started running about 25 psi at compressor shut-off, and air was noticeably cooler out of the vents. Now for the strange part. Air gets colder ONLY while compressor is running, warms back up when compressor kicks out. But the most disturbing fact is how the high side acts after I added refrigerant. The compressor kicks in when the low side is at about 45, and the high side is at 180. The low side gradually comes down to about 25, but the high side goes up to about 330-350, then starts dropping, and continues to drop while the compressor is running. Compressor cycle time seems legit, about 20 sec on, 20 sec off. I'm leaning towards there being a restriction somewhere, like a bad dryer, or a malfunctioning expansion valve. Anybody have anything different to suggest?
I'm leaning towards expansion valve based on how it's acting. Since you've cleaned the condesner that should rule it out. That's the most common restriction I've run into. Might be time to break it open and replace everything. The high side getting to that pressure is usually indicative of a restriction. My .02
2100 hrs on the clock. Can't even believe this is even an issue right now.
I wonder how well they assemble some stuff. We had issues with the linkbelt 210's around the same hours. I agree though it shouldn't be an issue.
Interesting. What kind of issues?
Pretty similar to yours, one had issues on the high side which had me second guessing my gauges. Wouldn't charge like it should and it would cool in weird patterns but I never watched it close enough to see if it had anything to do with the cycle of the compressor. One of them had trash in the expansion valve like they didn't clean the system before they sealed it up and pulled a vacuum. Not sure if I was the first to crack the system or not. The other ended up being a compressor, wouldn't get the high side up like it should be when charged properly. They were both around 2500-2800 hours when we finally broke down and fixed them but they had been acting up the previous summer. I wonder if they aren't run with partially plugged condensers and it works things just hard enough it kills a compressor. My A/C parts guy wasn't fond of the particular compressor brand when I came in for a replacement..... Same but different lol. I have run into a clutch that slipped. I had pulled my hair out and finally marked the two sides with a paint pen and with a strobe could watch the marks move in relation to where they were when it locked up. Kinda weird on that one.
Hi Shimmy1 It sounds like you have a blockage in your system for sure. I would not add any more refrigerant as it sounds as if it is all condensed and logged in your condenser at the moment. There is a gauze filter usually at the TX valve but most blockages occur in the filter dryer. I have had the desiccant bag burst open in the dryer and block the gauze filter on a number of occasions. Can you confirm what refrigerant you are running, approx what was the ambient temp of the day when you took those readings and what was the speed setting of your cab fan, and what approx rpm of engine. Cheers
134A, 80°F, I had the fan on both low and high settings, and tried engine rpm anywhere from 1400 to high idle. I ordered an expansion valve and new dryer today.
Hi Shimmy1 I am a little concerned about your original post where you said you would have liked to see your pressures. Typically to test your system you would open your cab door and run your internal fan at maximum speed and lift your rpm. This condition will open your tx valve to its full flow and also confirm you are not flashing in your sight glass also in this condition. on 134a you would be concerned if the pressure went much below 30psi as lower will begin to form ice on your evap. If you cannot get this pressure up it is sometimes low because of a blocked evap coil or air filter upstream of the evap coil. Based on your ambient and assuming clean condenser and allowing 10deg TD on the coil i would have expected to see around 125psi condensing pressure. Condensing Pressures can vary due to air flow but the lower the better. Just as a by the way automotive hoses are ready to burst when you getting 350 on the high side so i hope you were aware of how stressed the system was when you were testing it and adding refrigerant. Also very bad for your compressor in that condition as it burns the oil onto the valves with high discharge temps like that. Hope i helped Cheers.
The pressures are going to change with the ambient temperature and should be checked with MAX A/C and MAX BLOWER with ENGINE RPM at around 1500. If you are checking it at 70 deg F the 'normal' for 134A should be LOW= 35-40 HIGH= 145-160 . At 80 deg F LOW=40-50 HIGH=175-210 At 100 deg F LOW=50-55 HIGH=315-325 Your statemennt- "The low side gradually comes down to about 25, but the high side goes up to about 330-350, then starts dropping, and continues to drop" is NOT abnormal. What you are seeing is the operation of the expansion valve when the LOW side is too low. That is an indication of a LOW CHARGE, as verified by the low being 25 (assuming the HIGH went down to the 1XX psi range). You must wait for the readings to 'stabilize' to get an accurate reading. If it was me I would add 134 -while running and after it stabilized.- (AGAIN- assuming the HIGH is in the 100-200 psi range at 80 deg F.) Any 'drastic' difference between low-high pressures ONLY AFTER IT HAS STABILIZED would indicate a blockage or bad expansion valve. Of course if you replace the dryer you will have to charge it and it will work.
Hi CatKC, Are those pressures for his exact machine or general industry? Your saying he is condensing 45deg above ambient at 70 but more than 70deg above when ambient 100. Must have a very small condenser? Cheers
I am kind of lost on what could be causing this problem but when diagnosing something like this, I like to tape and insulate a thermocouple to the condenser outlet and measure the liquid temperature there. And compare it to the indicated temperature on the high side gauge. If it is a lot lower than the gauge indicates then you know you are slugging all your refrigerant into the condenser. If they are closer to even then probable low charge.
I don't know what you are saying "...condensing 45deg above ambient at 70" However condenser size is not relevant in pressure readings, as pressure is pressure. . . . . I will try not to get technical. Freon that is a -NOT under pressure has BOILING POINT. - Fahrenheit: R22= -42.1, R12= -21.6, R134(A) = -15.1. This 'represents' the 'capability' of the Freon to 'remove heat'. The A/C 'GAUGE/PRESSURE reading-is NOT any machine or device/car/truck/excavator specific,- it's only the representation related to the 'OUTPUT temperature which you are trying to achieve' and determines the acceptable readings. (I won't argue about what any particular mfgr SAYS) \ -Refrigerators/freezers have different OUTPUT temperature requirements and will have different normal readings. Different A/C's for a car/truck/excavator, Etc do have a different -AMOUNT Freon- required for a -full charge- (BASED upon a complete vacuum.) This 'amount' is determined by the SIZE of the COMPONENTS such as 'condenser', evaporator, hose(s) length, accumulator. The LOW/HIGH guideline readings registered on a gauge are based upon an STABILIZED operating unit at a specific ambient temperature with an assumed (engine RPM) airflow.
An OLD (as I am) check on a car and most outside vehicles (including excavators) , grab (CAREFULLY as it may be HOT) the - INPUT- to the compressor -AFTER- the A/C has stabilized (engine RPM, MAX A/C, MAX blower) . . . . . if it is COOL or COLD you are OK. If it's HOT . . .. . you might want to charge it (BUT ONLY if you suspect a leak. . which is common) Except for "WORD OF MOUTH" from someone,or passed along, that PAID for a fix...... As with anything, someone wanting to 'make a buck' will tell you -whatever-. In reality a 'sealed A/C unit will 'rarely' have a problem . . . . EXCEPT the number ONE cause. . LEAKS. I have worked for many years on A/C units (not as a JOB) and the common -money making- ( I should just say EXCUSE) thing with VEHICLES is a "DRYER" or "RESTRICTION" when it is 'nothing' but a 'low charge'. House A/C or refrigerator/freezer excuses are a little different.
I think you might have misinterpreted my reply. I believe he was referring to PSI. If not - correct me. My PSI readings refer HIGH - LOW pressures. Condensing and freezing temperatures of the ambient air or Freon were not addressed.
Hence my suggestion to measure the outlet temperature of the condenser while measuring the pressure. If you measure your subcooling on the condenser and it is a lot > 15° then you know you are packing it in and it is likely a high side restriction. If subcool is near zero then you are low on charge. Subcool is really the only way to measure in a partial charge assuming there are no problems in the system.
KISS- Keep It Simple S. . The high side -went down- after it ran a while and the system stabilized. The low side was low. UNLESS the high side STAYED high, which it did not . . it is low on Freon. Have someone replace the evaporator, clean the X, evacuate the system and recharge it. . . . of course it will work. Till next year when it will need more Freon. It will be difficult to find he leak, usually the compressor seal, as it is in a COLD climate and no one runs the A/C when 'it's cold' to 'lubricate' the seals. (Most A/C's won't run below about 30 deg F, even "Heat Pumps")
I'll try and simplify my previous response. It's likely low on Freon. The 'cycle time' is wrong and short (unless the ambient temperature is very low and/or the INSIDE temperature of the unit is very cold) because you are LOW ON FREON. The reason it cycles so quickly is because there are LOW and HIGH pressure switches in the circuit that control things. You are cycling too quick because your LOW pressure is saying "if I continue to run it will freeze the evaporator" so I must stop . . cycle. Whatever you do and decide to replace, once you open the system and 'evacuate and recharge' it will run. . . . . . .till next year.
- Restrictions - are considerably LESS frequent than LOW charges but are often used by A/C "specialists" to increase the cost of a repair. I only attempt to provide a simplified -non measuring device- method, if possible. Most excavator 'owners/users' have no A/C tools. They only want it fixed at as low a cost as possible.
Hi Guys I agree Birken with your condenser sub cooling test but most guys just feel with there hand down the sides of the condenser and you can feel where condensing stops. I agree with most things you say CatKC. If you interpret shimmy1 words exactly It can go both ways low on charge or blockage but yes most common symptom is low charge. If you have a blockage the high side will spike up condense and come back down again. A spike of 330-350 is high for a system that is not condensing full refrigerant flow but how long did it spike. So to simplify how can he have high condensing pressure if the compressor has sucked the evap low and is not moving alot of refrigerant (due to lack of charge). Typically i have found low charge will present low evap pressure and low condensing pressure. (Are his gauges Tip Top?) He said (The low side gradually comes down to about 25), usually with low charge the comp sucks the evap down to the cut out switch pressure very quickly. You need experienced eyes looking at the gauges when the comp comes in to gauge what is happening. A sight glass is invaluable at times like this I assume he has none? Bear in mind a simple cracked capillary tube on the tx will present like a blockage, so he needs to have a good look around for the obvious. If he reclaims the charge and measures quantity on new charge will resolve any lack of charge issues. Regarding High side gauge readings, what you see on your gauge when running is the (temperature/pressure) of the refrigerant when it converts from vapor to liquid inside your condenser. The size, condition, and efficiency of the condenser coil determine the temperature above ambient the vapor will condense and the pressure you see on your gauge. So by using your Temp/Pressure chart and knowing your ambient you can figure quickly what sort of pressure to expect on the high side gauges. In an automotive application where condensers are relatively small and not efficient they can have condensing temp/pressures 90deg above ambient. Not having seen what he is working on I do not know. Some pictures would of helped. The worst high condensing pressures I have seen are those little drop in units above the cabs with condensers in them the size of a shoe box. cheers
I thought I knew a little about A/C stuff. I don't know jack! Wow
The way I think of refrigerant systems is the opposite of the usual way. Most people tend to think of the system with the compressor compressing gas, condensing it to liquid, and then it vaporizes somehow and provides cooling. I prefer to think of it like this: Think of the compressor pulling down the pressure inside the evaporator. The tail end of the high side is a reservoir of warm liquid to measure into the evaporator and when it hits the low pressure zone it gets cold fast. If you have spent a lot of time working with propane or similar liquid gases that come in a warm pressure tank it is more intuitive. When you let liquid out you have the potential to make your fingers very cold. In the case of this problem we need to know whether the condenser is full of liquid or empty. I agree with the above that most systems I work on that have a lost charge will have both high and low side pressures low. I don't quite know what could be causing the high side to run so high especially when it was not that hot out unless something is not letting refrigerant through. It would also help to know whether the clutch cycling device is pressure based or thermostatic on this model and where it is located.
Could the high pressure reading be a fubar'd gauge? I overcharged one last summer due to a faulty gauge.
Thanks for the replies, guys. I've kind of put together what everyone has been trying to say, and I'm fairly certain the tx valve is plugged/malfunctioning. Based on Birken's suggestion to check the temp on the condenser outlet, I'm more certain than ever that the valve/dryer is the culprit. The outlet is basically ambient temp, while the inlet (where the high side check port is) is hot to the touch. I did try and add a bit of juice today, smd promptly had to let it back out because high side pressure immediately went over 400 when the compressor kicked in. My gauges are new, been used about a dozen times.
Birken, I knew you were the one talking about using a thermometer to measure cooling on an A/C system, but couldn't find your previous posts. After I read one of your posts earlier, I checked the temp of the condenser outlet. It is basically ambient temp, not warm at all while the inlet is hot. If you feel the low pressure side, the line going back to the compressor, it's cool (but not cold), and you can feel the temperature changes as the compressor cycles. Cooler while running, warmer when kicked out. Based on Junkyard's experiences with plugged tx valves, I'm going to change the expansion valve and the dryer. The dryer is cheap, and easy to get to. BTW, the current dryer has a sight glass, and it is clear. Too clear. In all previous systems I've worked on, I've always seen at least some bubbles in the glass. This one stays clear all the time.
Rig it up so you can start and stop the compressor with your eye on the sight glass and then watch it like a hawk while starting it from a good overnight. Should usually see some foam through there before it goes solid liquid. Then if you stop it you should see the liquid go back to foam and then vapor after some time passes. That is unless the high side is so far shut down that it will not drain the liquid in a reasonable time. Just another piece in the puzzle. If the system has dye in it the sight glass is much easier to tell, it will be green when full and clear when empty. Dump some dye when you are in there, good to have.
One more thing I forgot to mention earlier. I ran the system about an hour today, then shut it off. Dug for about two hours, loaded the hoe on the trailer, and ran down the road 20 miles at 60 mph. When I got to the yard, I hooked up the gauges before starting it, and the high side was at 140 psi, low side was about 115. Outside air temp was around 80°F.
Interesting that they were not the same. But I have seen some TXVs that do not open except when there is real pressure being generated by the compressor. The pressures you see at rest like that are related only to the temperature of the liquid in that part of the system. Be it an ounce or a pound of liquid the pressure will be the same at any given temperature. 140 psi = 107° probably the hot radiator nearby 115 psi = 96° probably some leftover heat source nearby
Hi guys sorry i missed the latest. Sounds like you are honing in on the prob. A lot of tx valves will not alow the system to equalize fully so is not a problem to see different pressures. At this point you could do some basic tests still. Chances are the receiver dryer will be ok prob tx valve problem. Assuming you have not over charged it to a point you will damage some thing you can check a few things at the tx valve. you can unscrew the capillary bulb off the leaving pipe of the evap and warm it and cool it and see if it is controlling the flow of liquid as it should. Some times we used to be lazy and just spray some coolant on the head of the tx if the bulb was hard to get to. If you see no changes on your gauges it would be high probability as the root cause. Cheers
Something I thought about while driving around. One reason the high side goes high when first compressing is that the compressor is (probably) a fixed displacement unit. Meaning the more pressure you give it on the inlet side the more refrigerant it is pumping per stroke. Then as the low side pulls down, the compressor is more "starved" for refrigerant and there is less being moved from low to high for a given RPM and the high side pressure begins to drop. There are a lot of variables in this concept but that is the general idea. I hope to learn how this actual project turns out when the OP gets it fixed.
I will most definitely post when I get it sorted out. I have decided to dig into the evaporator housing and make sure the coil doesn't have any sort of restriction on part of it. I have a new expansion valve and dryer, so if the evap and ductwork are clean, there really isn't much else to consider.
I agree with the above that most systems I work on that have a lost charge will have both high and low side pressures low. I don't quite know what could be causing the high side to run so high especially when it was not that hot out unless something is not letting refrigerant through. Perhaps this may help- The older terms are VACUUM (what a pump draws) and PRESSURE (what pump puts out) but I will relate this to LOW and HIGH. When an AC unit is -very low- on Freon both HIGH and LOW readings may both be lower than normal. However when an AC unit is -somewhat low- the expansion valve aka TEV/TXV/TX VALVE (or whatever you choose to call it) shuts off most of the flow of Freon, creating a -HIGH- high pressure reading. When an AC unit is -slightly low- on Freon the LOW side pressure (vacuum) gets low enough to the point to where the Freon -evaporates/cools- too quickly. When this happens the evaporator gets TOO COLD as the Freon is evaporating/cooling TOO QUICKLY. There is a small -tube- in the expansion valve that senses the temperature, which relates to pressure, of the evaporator. If the evaporator gets TOO COLD, the expansion valve RESTRICTS the flow of Freon, which results in a -HIGH- high pressure reading, to prevent FREEZING . This is the purpose of the valve, to PREVENT FROSTING/FREEZING/ICING of the outlet/evaporator. The evaporator must maintain a temperature above freezing or it will ice over and stop airflow. Whatever HIGH/LOW gauge pressure readings are considered normal will be slightly different and related to boiling points of different Freon's: F12= -21degF, F22= -41degF, F134A= -15degF at atmosphere, not under pressure. Refrigeration/AC is not complicated if one doesn't over think it.
With all due respect, the TXV will happily freeze an evaporator into a solid block of ice. Its purpose is to control superheat, not temperature. For those who haven't heard this before, superheat is the number of degrees above the boiling point that the outlet gas coming out of the evaporator is at. So you feed liquid into an evaporator which is running at 26 psi, the liquid immediately begins to boil and drops to 30°. It continues to boil on its journey through (getting all the air cold) until all the liquid is used up and what is left is just gas/vapor. The last few turns of the coils are adding the superheat to the gas so no liquid reaches the compressor. This is where the TXV will measure it, just as it is leaving the evap. Let's say it is 10° superheat, it will be 40° leaving the evap. The TXV does this by comparing actual evaporator pressure to the pressure of a little bulb full of refrigerant that sensing the outlet gas and a spring to add a little force to the valve, otherwise superheat would be zero. Now let's say the cab got down to temperature so the operator turned the blower to low. Now there is much less air warming up the liquid that is flowing through so liquid is getting closer to the outlet. Superheat is getting less so the TXV closes down. Superheat goes back up to the setpoint, but what happened to the pressure inside the evaporator/suction? It dropped way down because there is less refrigerant flow into it. Now let's say the evaporator is running at 18 psi. This means the refrigerant coming in will be boiling at 19° which will quickly turn the whole mess into a block of ice. So there is another temperature sensing element that either senses the actual (absolute) temperature of the evaporator, or the pressure inside, (sometimes a variable compressor). It will stop the compressor pulling vacuum on the evaporator in order to allow the temperature to rise above freezing, then start the system again.
Sounds like your txv is bad.
Update. Since now I'm having engine trouble (again) I was in the diagnostic menu today, and found there is an A/C diagnostic screen. After watching that for a bit, found that the evaporator temp is running between 41° and 43°F while the blower is on high speed. An increase in air temp at the vents without a corresponding increase noticed by the ECM would suggest a restricted evaporator. Dug into it this evening, there appears to be no access to the evaporator housing without completely disassembling the inside of the cab, including the multiple ECMs and assorted wiring harnesses. Junkyard, have you had to get to the heater core/evap/blower motor on one of these yet?
I was able to clean them through the filter door on the 210's. Some suck for that type of access.
Spent some time today working on it. Unplugged all the harnesses from the ECMs, and was able to remove the rather large plate they were attached to. Had plenty of access at that time to the heater/air unit, but aside from being able to pull the blower motor, could not disassemble any thing else without pulling THE ENTIRE ***** UNIT. Not sure if the whole plastic POS mess just lifts off the evap and heater core, but without a service manual, I stopped there. Removing the blower motor did nothing, but after I pulled the resistor block out of the housing, I could kind of see the evap. Had plenty of dirt/mud/whatever all over it. Not sure how that crap all got in there, since the fresh air and the re-circ air both have filters, but hey, nothing on this machine surprises me at this point. Took a water hose, blowgun, and shop vac and cleaned it off best I could thru a 2" square hole. Blew air up thru the drain tubes, sprayed water, blew air, so on and so forth until I had clean water running out the drains. It works considerably better, but I don't believe it's 100%. Thinking about setting it on fire, since now I'm having engine troubles again. You'd think engines could run more than 2000 hrs with today's technology.
Will the manual for a cx210B help you?
Thanks for the offer, but I looked up a B with the online parts manual, and the systems are completely different. I just wish these dip***t engineers would not assume that everything will live forever, and figure out how to allow service without removing EVERYTHING.
How about a CX350D
That's the one.
I have a caterpillar chart I'll post up tomorrow. I would evac system. It's obviously not leaking but double check it hold vacuum. Should pull 28-30in. Then replace dryer and expansion valve and make sure the evaporator isn't clogged with dirt
The evap was/still partially plugged up. Since I can't access it without stripping the entire HVAC unit out, I cleaned it best I could. Thanks for the advice, but I'm not going to open the system.
The dust gets through the filters because the filters are designed to protect the evaporator and heater core from stuff big enough to plug them, but the dust that gets through sticks to the wet evaporator, then it grows fuzz overnight, then it forms a nice wet mat that filters the air much better than the factory filters, trapping lots more wonderful nutrients. You did the right thing by blowing it out as best you can with air and water. If it causes problems again, see if there's anywhere you can add some access holes to spray water at a better angle.
Good luck
do you know that the a/c system has some sort of computer control that controls the output. The sensor is that little black dot on top of the computer LCD screen about the size of a nickel if it's not clean(Dusty) or shaded ( so tinted windows confuses it) it won't let the a/c cool correctly they tell me it's supposed to keep it from over cooling just more B.S to break
The A/C system -is not- controlled by the light sensor. The sensor sometimes controls such things as lights and console lighting, depending on the device. A/C systems are quite simplistic in function and operation. -Their output- (airflow, Etc) is -sometimes- controlled by temperature sensors but never by a light sensor.
Actually, on these particular Case machines, the light sensor does affect the cooling, IF the ECM determines that it needs to. I know this because there is a diagnostic screen for strictly the A/C system built in. It reads a multitude of things, among them the evap temp, incoming air temp, and sun load. Not trying to be a smartass, but it is a fact. Also, I notice that it isn't a perfect system, because it will run cooler on a bright, sunny day than it will on a cloudy day. On my machine, I will have to set the target temp higher on a sunny day than cloudy, also need to turn the temp DOWN when the sun goes down and it's still hot out.
I had an Infiniti car that had a system that worked exactly as you described. Except it worked well, as intended. You set the desired temperature and if the sun was pouring in it would run the fan a little more to make sure you felt cool, or the right temperature.
You learn something every day, that's a new one on me. I knew a few auto's had similar sensors but I've never seen a Case with a sensor that also controls the A/C. Next time I'll keep my keyboard (mouth) shut unless/until I see a wiring schematic. . . Better no response than incorrect response or misinformation.
CNH cannot seem to design a HVAC system that works, especially auto temp systems.
Agree. And when a manufacturer/someone starts screwing with a 'basic function' such as AC intending to make it more 'modern' and apply 'computers' for control, it only makes it more difficult to diagnose what is likely a 'simple problem'. Then it takes the 'diagnosis' out of the hands of the individual, whom is confused by all the 'computer controls' or the 'words/acronyms' used by someone that -may- want to charge for unneeded work. I know computers and computer controls and always use K.I.S.S. as my guideline. I've saved many . . . .money, by fixing "expensive" repairs for very little, as the 'repair' was simple. Auto temp (and the controls) are another way to insure the current hedonistic society is satisfied. Personally, I don't mind turning a knob up/down to adjust the temperature.