AC was cooling fine yesterday & early this AM. I blew out exterior of radiator & condenser with an "air comb". Not much dust or chaff blew out. Cleaned both cab filters. Checked to be sure AC comp belt is snug. Installed AC gauges,pressures were 52# & 300#. I think orifice must be clogged. This AC system hasn't been disassembled since I purchased it used with 137 hrs on speed/hour meter in 2012. Thanks for any ideas,Jim
Warm air coming out of vents with AC operating on M7040?
- Thread starter Tx Jim
- Start date
How is the evap? Does the air coming from it smell musty? Sure sign of a plugged orfice will be a fast cycling of the compressor, does it fast cycle?
Nothing worse than a glass BBQ in Texas heat....
Nothing worse than a glass BBQ in Texas heat....
As an aside, the ac system in my M9 wasn't touched until about a month ago and it's a 2004 with just shy of 2000 meter hours.
When you measured the pressures, what was the outdoor temperature?
Prior to connecting linesets, were the lines flushed of air using refrigerant?
With a thermometer in the vent, what is the temperature of the cooled air, and what is the temperature inside the cab and ambient outside?
Prior to connecting linesets, were the lines flushed of air using refrigerant?
With a thermometer in the vent, what is the temperature of the cooled air, and what is the temperature inside the cab and ambient outside?
Jim
It was working, now it's not, and pressures are too high.
Not enough heat is being dumped by the condenser. Blocked or not getting air flow? or,
expansion valve opening too far, too much liquid into evaporator. Maybe Flip knows if the expansion device is thermostatic, as I see a reference to a heat tube that must be aligned. Is it possible the heat tube got knocked out of position? Is the heat tube a sensing bulb for the expansion valve?
My suggestions to check first. Also, is the low pressure line sweating or cold, or is it not?
It was working, now it's not, and pressures are too high.
Not enough heat is being dumped by the condenser. Blocked or not getting air flow? or,
expansion valve opening too far, too much liquid into evaporator. Maybe Flip knows if the expansion device is thermostatic, as I see a reference to a heat tube that must be aligned. Is it possible the heat tube got knocked out of position? Is the heat tube a sensing bulb for the expansion valve?
My suggestions to check first. Also, is the low pressure line sweating or cold, or is it not?
Jim
Did the end of AC output occur and then you cleaned out the heat exchangers, or did cleaning the exchanges result in no AC?
The system is trying to maintain certain pressures, mostly the evaporator pressure, through an expansion valve and cycling the compressor.
You don't mention what the AC compressor clutch is doing. Running all the time, cycling or not running most of the time.
The factory WSM contains an easy to follow test procedure which has you bypassing all controls and powering the compressor continuously from the battery for 5 minutes to allow the system to stabilize all the while monitoring system pressures and the presence and frequency of bubbles in the receiver sight glass.
Having the same year M7040 makes me think that you too have a very small leak and the system has just lost enough gas to stop running.
Getting into an extensive investigation will involve opening the system with all that entails.
18 wheeler's AC are serviced all the time by mobile mechanics who come to you. At this stage, a Kubota mechanic is not necessary. What you want is a through leak detection, perhaps with the addition of a UV dye, and then a recharge.
If the recharge does not get the pressures into the proper range (which at 86F outside air would be 21-28 psi and 185-242 psi.) then more involved work is necessary which will be much more expensive.
My suggestion is a bit of a gamble but one I think is worth the risk.
Dave
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TX Jim. Try pinching off the heater hoses coming out of the block to make sure that the heater control valve is not leaking by. If it is putting a little heat in the cab, it will warm up the ac side shutting it down. A fairly common problem.
Are those pressure readings at idle or higher RPM? Restrictions in the orifice (or expansion valve which I believe all kubotas use just from reading here) would cause your low side to be real low pressure.
Those pressures are somewhat normal to what I see here next door in LA this time of year on a vehicle at idle in the shop. Slightly high but like Dave said did this start after cleaning the condenser? Is your low pressure line cold to the touch?
If those are idle pressures what are they if you run the rpm up?
Those pressures are somewhat normal to what I see here next door in LA this time of year on a vehicle at idle in the shop. Slightly high but like Dave said did this start after cleaning the condenser? Is your low pressure line cold to the touch?
If those are idle pressures what are they if you run the rpm up?
No fast cycling of comp clutch. Air didn't smell musty but I've never inspected evaporater. I agree about Texas heat. Several yrs back I rd baled for 4 hrs with my JD 4255 with inoperable & when I exited the cab I was wearing not one piece of dry clothing. I told self "never again"!!!!. I have an AC tech coming to check it out today.How is the evap? Does the air coming from it smell musty? Sure sign of a plugged orfice will be a fast cycling of the compressor, does it fast cycle?
Nothing worse than a glass BBQ in Texas heat....
Dave
AC quit cooling then I blew out rad/cond. Pressures didn't change much with higher rpm's. I'm beginning to wonder if my trainee tractor driver inadvertently turned heater on?????
AC quit cooling then I blew out rad/cond. Pressures didn't change much with higher rpm's. I'm beginning to wonder if my trainee tractor driver inadvertently turned heater on?????
Pressures need to be checked with the engine at 1500 RPM and ambient at 70 or so. I bet you have no issue with the 70. On my M9, It's impossible to have the heat and ac on at the same time. The controls won't allow that.
One thing I did that makes a substantial difference in ac operation at lower engine rpm, is, I added a 12 volt automotive pusher fan in front of the condenser and wired it to a relay that energizes when the ac compressor clutch energizes. Kubota's (at least mine) suffers from limited air flow through all the heat exchanger's before it even gets to the radiator.. Between the condenser is the transmission oil cooler, the air to air charge air cooler, 2 sets of screens and then the radiator so adding the pusher fan improves the airflow and low engine fan speeds and I can idle the engine and still have excellent cooling in the cabin. The motor runs cooler as well. More ambient air flow equals better cooling.
Heater control was in off position. For a diagnostic step I will still put vice-grips on heater hose. My M7040 AC has cooled very good i the past
The controls are simple. A temp dial to adjust both heating and cooling so you cannot run heating and cooling at the same time.
I button to turn on AC compressor.
I am still with my tentative low refrigerant diagnosis.
Again, what is the compressor clutch doing?
Dave
Dave
I overlooked your question about comp. When comp clutch engages it stayed engaged while I was checking tractor.
I overlooked your question about comp. When comp clutch engages it stayed engaged while I was checking tractor.
After further diagnostics I noticed pressures will not equalize when comp. is turned off leading me to think tractor has a clogged expansion valve.
Jim
The fact that the system does not equalize is a big clue.
What do you think could be clogging it?
Is it possible refrigerant has ever been added?
This is a question not a statement: If the valve is clogged how do the evaporator pressures get so high with the compressor running?
With refrigerant gauges, (mine included,) that are used infrequently and perhaps only on one machine, I often wonder how accurate one or both gauges are. It is not like you can swap them to see if they both read the same.
When this is solved please post the final cause.
Dave
I don't remember ever adding refrigerant since I purchased tractor in '12 BUT I could have forgotten. I'm waiting on new expansion valve.