AC pressure readings and problem with dealer.

fastline · Aug 14, 2022

@John C.
just for clarity, I wanted to point out that the book page 70-10-2 diagram provided by Doug is wrong! As is common in books that misprints happen, the diagram seems to show a separate TXV bulb connecting to the vapor line. that setup would be common in a stationary system, but is in fact wrong here, and even the plumbing is wrong. Figure 70-10-5 shows the correct TXV for this application.

It can get really confusing when in the learning stage and get inaccurate material! The "thermostat" they show in that diagram is the temp switch, and they commonly stab them right into the evaporator fins to get the most accurate reading possible.

Doug580l · Aug 14, 2022

John C. said:
Birken: Thanks for the links and the references. They are a great aid in understanding what is supposed to be happening in a properly operating system. I can see now that just putting a set of gauges in the system might not be the whole answer to troubleshooting a problem. I very much doubt that any wrenches in the industry carry a chart that would let them know if the system is properly charged.
fastline: It sounds like you work on these systems all the time and have developed your instincts and procedures for troubleshooting. I appreciate now that there is more to it than just plugging in gauges.
Doug580l: Thanks for the diagram. It helps a lot by providing the graphic showing the metering valve and the bulb placed by the output of the evaporator. The diagram does not show it being connected to the vapor stream and instead indicates it is in the air stream monitoring temperature of the air through the evaporator. That is like the systems I am familiar with.

Since the machine is new and under warranty you shouldn't be messing around with the system until you have no other choice. You may think you are there now. After making sure that you operate the system the way it was designed, cab closed and the cab air flow recirc is on. I would suggest that you run the machine in a test of actual system operation in the conditions that make the problems occur. Write down exactly what is happening and a time for each check you do. You may have to do this in front of the dealer salesman or service manager. Make the paper legible by typing it out if need be. I would next write out questions at the bottom of the test paper. You will need to convince a manager or factory rep that there is an issue and create doubt in people's minds that the troubleshooting was completely thorough.

What was done when the technician checked the system operation?
Gauges plugged in? What were the readings?
Was the covers over the evaporator unit removed?
Was the operation of any heated air door checked?
Was the temperatures of the inlet and outlet to the evaporator checked?
Were those readings checked for proper system charge?
Was the unit tested when the ambient temperature was around 90 degrees?
Were the drains removed and blown out to make sure there was no plugs?

Last thing to bring up is that manufacturers very commonly assemble new machines with minor glitches. Perhaps there is some insulation covering a ducting connection. Maybe the evaporator is partially blocked. Maybe the bulb for the metering valve is covered or in the wrong place. All these things create some doubt in the manager's mind that possibly the technician didn't do a complete job of troubleshooting possibly because he wasn't fully trained. You might even consider finding a qualified outsider to check the system in the dealer's shop. If that person says its right then you pay, if he finds something wrong, then the dealer pays.

I know it is a pain and you didn't buy a new machine to have to go through all this but it is unfortunately part of the process when things like this occur.

Good Luck!

Excellent advice John, thank you. All very logical. I am having difficulty with logic lately by letting this bother me more than it should. It just pisses me off to spend that kind of money and then be lied to and ignored. I am waiting to see if Bobcat corporate responds. I doubt that I will get the dealer to agree to anything since they claim that everything is working as it should and it's been a fight to get them to look at it after the first time. The last time they looked at it they made me wait 3 weeks. They refuse to give me any paperwork for the last 2 services so it's hard to know what's been done already. Although something has been done the last 2 times because the ac acted different after each service. I am leaning toward bringing it to my Case dealer if they will work on it. Also considering selling it since I would never bring it to the dealer for service once the warranty is over.

It may be some kind of glitch like you said. I never felt the ac was working right since I got the machine(March) but it became obvious as the outdoor temperatures rose.

It's interesting that you stated to operate the machine in the conditions that make the problem occur. I was using it today and I noticed that it acts worse when the machine is being operated rather than just sitting at full throttle. I was trying to take more videos as the vent temps were fluctuating about 10 degrees (50-60 and later 53-63) while on the coldest setting and blower on high. When I would stop operating it and try to take a video it would only fluctuate a few degrees and generally be colder-52-54. When I was using the machine in the morning at around 78-80 degrees out, there was a lot of water coming out of 3 vents. Seemed like twice as much as the videos I posted. Then later in the afternoon when it was in the upper 80's there was much less water coming out of the vents but that's also when the vent temps were higher, up to 63 at some points. It may of been more humid in the morning.

JD955SC · Aug 14, 2022

A lot of people make the mistake of AC performance checks in cooler temps such as morning, in a shop under cover, etc.

If you bring me a problematic AC unit I want to be testing it on a hot sunny day for maximum diagnostic reliability.

Doug580l · Aug 14, 2022

Got another video of ac. With the water blowing out of the vents I opened the cover to show the water inside. It was about 82 degrees out when we shot the video. Lots of water.

fastline · Aug 14, 2022

Doug580l said:
Got another video of ac. With the water blowing out of the vents I opened the cover to show the water inside. It was about 82 degrees out when we shot the video. Lots of water.

I am starting to smell something. I think a really good HVAC tech should look at this. What I suspect is possible air bypassing around the evaporator.

Let me explain, if air is allowed to bypass the evap coil, it will give you ALL the symptoms you are experiencing. Low head pressure, cycling, high vent temps, etc. Basically you absolutely HAVE TO confirm that all the air moving through that system is being forced through the evap coil and the fact that you can so easily remove that cover and expose everything is eye opening! You NEED to look at how air gets sealed here. That is the first part.

I honestly can't make heads/tails of the air movement and such here. It really appears that whole design is a mess. There should never be water all over the blower and electrics of a system. That thing will fail is short order! Keep at it! Send this crap all over the web and a guarantee you will force Bobcat to deal with it, and I would tell them to write you a 'special' check to remove the content. I have received exactly that when I exposed stuff like this. No way is that a good design!!!

Birken Vogt · Aug 14, 2022

My thought as well. I don't fully grasp air flow either on this one. Are we looking up down or sideways here?

I have a dumb aftermarket AC in my old F250. It has a core that is much too small for the ductwork. It never worked until we sealed it off. In my case long outside of warranty. The old trick for air flow is to use the plastic foam pipe insulation in various sizes and stuff in the gaps. I like to smear with gorilla glue first so it stays where I put it. But also put it in snugly. Worked for me.

Doug580l · Aug 15, 2022

fastline said:
I am starting to smell something. I think a really good HVAC tech should look at this. What I suspect is possible air bypassing around the evaporator.

Let me explain, if air is allowed to bypass the evap coil, it will give you ALL the symptoms you are experiencing. Low head pressure, cycling, high vent temps, etc. Basically you absolutely HAVE TO confirm that all the air moving through that system is being forced through the evap coil and the fact that you can so easily remove that cover and expose everything is eye opening! You NEED to look at how air gets sealed here. That is the first part.

I honestly can't make heads/tails of the air movement and such here. It really appears that whole design is a mess. There should never be water all over the blower and electrics of a system. That thing will fail is short order! Keep at it! Send this crap all over the web and a guarantee you will force Bobcat to deal with it, and I would tell them to write you a 'special' check to remove the content. I have received exactly that when I exposed stuff like this. No way is that a good design!!!

Wow, Starting to feel like it might actually get fixed now. What I don't understand is what they do at each service to make it worse. It never leaked any water before and after the first service, where they did nothing as far as I can tell. After the second service it started leaking a little water and did get colder. After the last service it's leaking a lot more water.

I'll take a look at it and see if I can figure out how to check how the air is getting sealed. The cover is all plastic with no rubber etc to seal around the evaporator. I'm including a pic of the cover.

Doug580l · Aug 15, 2022

Birken Vogt said:
My thought as well. I don't fully grasp air flow either on this one. Are we looking up down or sideways here?

I have a dumb aftermarket AC in my old F250. It has a core that is much too small for the ductwork. It never worked until we sealed it off. In my case long outside of warranty. The old trick for air flow is to use the plastic foam pipe insulation in various sizes and stuff in the gaps. I like to smear with gorilla glue first so it stays where I put it. But also put it in snugly. Worked for me.

Here's a few pics of the system.

Vetech63 · Aug 15, 2022

Looks like a lot of dirt has gotten in there. That evap core needs cleaned. Has the heater core lines been plugged off yet?

Doug580l · Aug 15, 2022

I checked the Bobcat parts site to see if maybe there is a gasket missing from the cover. It doesn't show one but it does list insulation tape, sold by the foot but doesn't indicate where it goes. It does show that there is supposed to be a specific insulating tape by the thermostat.

Doug580l · Aug 15, 2022

Vetech63 said:
Looks like a lot of dirt has gotten in there. That evap core needs cleaned. Has the heater core lines been plugged off yet?

No, I'll try to do that today, fastline has suggested that several times. Very hard to see them. I assume if I find them I can carefully put a vice grip on them?

Doug580l · Aug 15, 2022

Vetech63 said:
Looks like a lot of dirt has gotten in there. That evap core needs cleaned. Has the heater core lines been plugged off yet?

I did clean the evap core about 20-30 machine hours ago with compressed air. Is it normal for it to get so dirty so quickly? Is there another way top clean it?

Tinkerer · Aug 15, 2022

You could locate one of the heater hose connections on the engine and install a ball valve to stop the hot coolant from going into the cab.
I did it on both hoses in my backhoe and it made a big difference on hot days.

Doug580l · Aug 15, 2022

Tinkerer said:
You could locate one of the heater hose connections on the engine and install a ball valve to stop the hot coolant from going into the cab.
I did it on both hoses in my backhoe and it made a big difference on hot days.

Good idea, ordered a couple from amazon.

fastline · Aug 15, 2022

Doug580l said:
Wow, Starting to feel like it might actually get fixed now. What I don't understand is what they do at each service to make it worse. It never leaked any water before and after the first service, where they did nothing as far as I can tell. After the second service it started leaking a little water and did get colder. After the last service it's leaking a lot more water.

I'll take a look at it and see if I can figure out how to check how the air is getting sealed. The cover is all plastic with no rubber etc to seal around the evaporator. I'm including a pic of the cover.View attachment 266018

Either something is missing or that is just a pathetic design, guaranteed to give you problems forever! This is a dirt machine. that intake for air should have a good and well sealed filter on it. If it doesn't make it that way! Why take it serious? Look at how quickly you are fouling the coils!

You need to go around all 4 sides of the evap coils and either confirm they get sealed, or make them seal! A thick foam strip is probably what is needed on that plastic cover, even if the OEM never did it. Actually that whole panel needs a good seal, and it should both have a seal, AND be screwed into place.

You can 100% bet air is going right around that evap. Whether this will solve anything with the water issue is not certain. the whole thing is confusing.

Remember when I mentioned about checking the suction line temp???????? Yeah, problems like this would have been spotted a LOT sooner.

If the evap is running super cold because of the short circuit of air, that could explain the wild condensate issues.

Doug580l · Aug 15, 2022

I crimped the heater hose by the heater valve and ran the machine for about 20 minutes. Didn't seem to make much of a difference. Vent temps were about the same and there was water coming out of them. I did notice that the compressor seemed to be cycling every minute or so.

Doug580l · Aug 15, 2022

fastline said:
Either something is missing or that is just a pathetic design, guaranteed to give you problems forever! This is a dirt machine. that intake for air should have a good and well sealed filter on it. If it doesn't make it that way! Why take it serious? Look at how quickly you are fouling the coils!

You need to go around all 4 sides of the evap coils and either confirm they get sealed, or make them seal! A thick foam strip is probably what is needed on that plastic cover, even if the OEM never did it. Actually that whole panel needs a good seal, and it should both have a seal, AND be screwed into place.

You can 100% bet air is going right around that evap. Whether this will solve anything with the water issue is not certain. the whole thing is confusing.

Remember when I mentioned about checking the suction line temp???????? Yeah, problems like this would have been spotted a LOT sooner.

If the evap is running super cold because of the short circuit of air, that could explain the wild condensate issues.

I'll take a look at what I can see around the evep. coils. I may have to remove the dash in order to see the back of it.

I think that I will put tape all around the cover to seal up any potential leaks from there and see if that makes a difference.

We checked the evap coil temp when the cover was off. Think it would get to around 38 degrees or so. I did notice the coils get a little frost on them before the compressor would kick off and it would quickly melt off.

Welder Dave · Aug 15, 2022

Not an AC expert but since that plastic cover has a coarse foam filter, it seems like everything else should be sealed so all the (intake) air has to go through that filter. On a vehicle if you don't clean the cabin filter you can take out your heater/AC motor because it's trying to work too hard to pull air through a clogged filter.

fastline · Aug 15, 2022

Doug580l said:
I'll take a look at what I can see around the evep. coils. I may have to remove the dash in order to see the back of it.

I think that I will put tape all around the cover to seal up any potential leaks from there and see if that makes a difference.

We checked the evap coil temp when the cover was off. Think it would get to around 38 degrees or so. I did notice the coils get a little frost on them before the compressor would kick off and it would quickly melt off.

No, I don't think you quite understand! Yes that cover needs sealed well, but what keeps air from going right around that evap coil where that cover goes? That should have a seal on it. You would be putting foam on the end of the evap. I would shove a healthy strip between those copper Ubends that would engage the cover when it is installed. Think about this. The blower is pulling air on the left. Air will enter on the right of the coil. Any air leaks means air will go around the coil, not through it.

As well, it is nearly impossible to test suction or evap temp with that cover off! there is no air going through it!

Doug580l · Aug 15, 2022

Just checked the machine again. Ran the machine about 20 minutes then pulled the hvac cover off. I thought I checked the heater core temp before but I must not of. With an infrared temp gun, the evap coils got as low as 29 degrees, but the heater core was between 60 and 62! And the heater core dropped a couple degrees after the ac was shut off. I assume that would cause most of my issues? I had vice grips on the heater hose by the heater valve but maybe it's not a good place or not stopping the flow. Hoping were closer to solving it now.

AC pressure readings and problem with dealer.

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