D8T waste handler chucks ice cubes at idle, operators complaining that it doesn’t AC when worked. AC had over double charge when we finally got a real robinair machine. Replaced low pressure switch. What are my next steps to **** up the operators besides “I didn’t have AC in Iraq.”?
Is the evaporator clean? Do you have refrigerant gauges? Can you share the high and low side pressures, both at idle and rated speed? How much charge did you install? Care to share the serial number, or, at least the prefix? There are 8 different prefixes for D8T machines.
Evaporator is clean. I have gauges, but we’ve been too busy with other machines in the shop for me to go down to the shop and check. Machine called for 1.7 kg, so after I pulled 3.7 kg out, I recharged to the proper amount. Prior to us getting a proper AC recovery/recycling machine, the older mechanic just added refrigerant until AC blew cold...
Chances are the condenser fan(s) are not running, at idle may see enough low refrigerant flow to cool Some but as speed and pressures increase heat just builds. That and filth in Both cores, Condenser and evaporator, that will retain water on the evaporator side and freeze up as soon as drops to cold enough. These do/should have filters in them that need cleaning or changed unless previous hammer head took them out for His convenience.
As above. Have you checked both the fresh air and recirculation filters.? I assume this machine is a waste disposal arrangement so it may even have a turbine precleaner with a third element in it. I also assume that the AC filters will be the activated charcoal version for odour control. How about a Serial Number..? Where is the AC condenser mounted.? Under the hood, on the RH fender, or on the cab roof..? Might also need to dig into the dryer and/or the accumulator, but that can come later - basics first.
I'm back on the clock Tuesday. I can't promise answers then, but the dozer in question is sitting in my shop right now. The previous mechanic was old-school, the current secondary is a blonde's hair from retirement, and I'm on my second retirement. I'll lay down with proper answers and a SN.
Gauge readings are everything in a scenario like this. Under various conditions.
I won’t be back at work until Tuesday (two four day weekends a month), but the machine will be in the shop. I’ll try to update all the questions then.
1. Need gauge readings. 2. Notice when the blower fan is on high...……..does it sounds like a hurricane and is there a lot of air blowing through the vents.? 3. Are ALL the condenser fans on and running? 4. Does the compressor cycle electrically?...……...and how often when running? If it is cold when you first start it up, you are probably dealing with evaporator freeze up......especially with the high humidity in the area lately.
I know its a stretch, but if you can get the operator to avoid running the a/c on max cold in high humidity conditions, the evaporator may not ice up. this could be a classic case of less is more.
Generally on High Cool max air flow the systems will have a Recirc Mode for cabin air, that should eliminate the freeze potentials.
The nature of frost can tell you a lot: if the TXV it self is block of ice then there’s restriction there! If only part of coil frosted than its low on charge. But with construction machine I suggest everybody to start with evap. air flow! Due to nature of operating conditions cabin air flow is a main culprit!!!
I think yunz are missing that it may be a thermostatically, computer, controlled system. When I picked a random D8T in the parts manual (sonce no one provided a serial number), I saw temperature sensors in the ductwork. Is there a digital control panel? Knobs?
Well if the low side gauge starts out somewhere reasonable and then goes way into the 20s and teens on the °F scale after running a while you know you have a failure of whatever part keeps the evap from freezing. You need gauges and thermometers to know what to chase first.
Electronically controlled Solenoid/expansion systems? Or relying on a expansion orifice as so many now do?
Gentlemens, I will be at work tomorrow and, barring my shop being filled with mission critical equipment, will put gauges on the machine, get the serial number, etc. This is how the shop looked Wednesday. Wait, can I not upload directly from my phone? Boo!
Steady work, good rule of Job Stability.
Most of the cat excavators I've touched lately are expansion valve with a thermo probe in the evaporator. Dirt restrict air flow, evaporator gets too cold, probe opens clutch circuit.
I can’t get the operators to use the engine brakes on our 740Cs, which causes high brake temp codes, you really think I can talk them into using less AC? These are government workers, they start an hour late and turn in an hour early!
We run all of our equipment air conditioners with all the doors/ windows open. I don't see freeze over on any of them.
Where'd you get the 1.7kg charge amount number from?
The data plate that tells me the AC charge inside the cab.
How about that serial number, then?
it's 1040 pm CST. I don't have to actually start moving equipment until 530 am tomorrow, so how about some patience?
Patience? Yeah, yeah, patience. I can be patient. I'm good at being patient. My babysitter is always telling my mom how patient I am. I'm really, really good at being patient. Someday, when I grow up, I'm gonna be a doctor, and I'll have lots of patients.
You forgot smileys!!! Who knows, someone might take it serious!
TBH until the filters (and the question does it have two or three filters has been answered) have been checked and pronounced good I wouldn't go any further than that with diagnostics, especially on a machine that works in a landfill application. We replace both fresh air & recirc aircon filters in our large T-Series tractors every 250 operating hours, and they often come out looking like they are caked with concrete the dust on them is so hard.
Filters- it has 2. Replaced every 250. SN- kpz03799 Sorry, all I can give you today. Looks like I’m in the shop by myself for the next week or so and I’m up past my balding scalp in iron.
Found this
Ok, so it's a roof-mounted condenser. If both the fans are working and the condenser is clean then I'd suggest replacing the dryer as a first step. I'd pretty well guarantee that it's never been replaced before - we replace ours every year. The great thing is that it has self-sealing couplings so no refrigerant will be lost making the replacement. After that it's probably gauges time.
I replaced it last year. I remember it because on this machine and our 836H had their quick disconnect dryers and lines replaced by the old mechanic with the old stile “thread on.”
You wouldn’t happen to have a pdf of that, would you? It would be even sexier if that doc also had compressor oil type and quantity.
You guys mention ac filters several times...on my cat excavators, even with religiously serviced ac filters, I still get blocked evaporators. I think I've disassembled most of them by now, to blow out the cores. Some will let me use a 90° wand to mostly clean them, usually thru the blower resistor hole.
I really don’t want to do this. It seems like every design engineer had his wife impregnated by a mechanic, and spends the rest of life putting important things in stupid places.
Here ?
Bless you sir. The only documentation on AC we have is the previous mechanics service notes in the equipment books. The same guy who just added until the low side got frosty and the AC seemed cold. Dude taught me a lot, but a lot of his methods were based around saving as much money as possible and some of those techniques involved random modifications to machines to keep less parts in inventory.
Okay, Johnny, you've got two days to read all that and get ready for the AC test latter this week!
Looks like it’s nothing but vodka and red bull for the next two days.
I run pag 100 in all sanden compressors . But to be honest i wouldnt worry about oil quanity to much as the only way to know for sure is to dismantle system flush it clean drain and refill the compressor then finally add appropriate amount of oil for all components in the system to recoat them . That usually only gets done after a compressor failure. And then the compressors already come with oil in them so only need to add for the components that are now dry. On further note the way you explain the old man mechanic, if he did stuff the way all the old guys seemed to and add a little oil on each charge up it very well could be slugged full of oil also causing cooling problems. I currently have a few truck in my fleet in suspect of that , my fix for those when i have an ac machine handy is to evac, throw out drier unhook lines from compressor use blow gun and blow thru all components to see if tons of oil comes out , hook all back up and vacumn and recharge . I usually replace expansion valve at this point also . Keep on keeping on garbage is rough did it for 8 years 5 on trucks 3 on equipment repair.
Cat doesn’t usually specify oil weight.
It's in there if you look hard enough
If it is the common Sanden compressor found everywhere it has an oil dipstick and their manual has instructions for reading level depending on mounting angle. Might be worth checking to see if it is overfull. I agree about the old time mechanics always adding 2oz of oil every time they change an o-ring or do anything. But I have not fixed a problem by doing this, just throwing it out there.
I wonder what the thought process was on that. We go the other way, machines that don't have quick-connect couplers on the dryer we replace them with QC simply to make replacing dryers easier. Either way, we would replace a dryer after a year of service, so by our standards that dryer is due for replacement. Not saying it's the cause of your problems though. It would appear that the "old school seat of the pants" method as practised by your predecessor might have got you further into problems. Is this the time to suggest a full system evac, clean out the unknown qunatity of PAG oil you have in there, and start again..?
I agree with the cleanout and start from fresh. A/C is so touchy and aggravating sometimes it’s better to do everything possible to start with a clean slate
As silly as it sounds, his thought process was that we already had one machine that used a particular part number dryer, and since the only difference in his opinion was the connections, we may as well only stock that same dryer. Since his retirement, I've cut back on what we keep on hand, because our dealer can almost always get us a part by the next morning, I don't see the need to have shelves and shelves of items that may not get used in a year or more. Don't get me started on what he did to a Komatsu 155 AC to cut back on costs. I'm not going to reconvert the system, because I don't have that kind of time, I'm just going to roll with it. Home with a sick boy today, depending on what gets broken today, I'm going to get started on that D8 tomorrow. I'm sure that my shop will be filled up with mission critical equipment today because the boss is running some of it.
OH NO! Not letting the boss run equipment are you? Miss one day and you will be spending till Thanksgiving trying to catch up! Hope the sick boy is feeling better.