Dash AC not cold

[buystockinfun]

I'm wondering if my expectations for my Dash AC are set too high. It just doesn't seem to blow very cold. When it is about 85 out it comes out about 63 out of the dash with an AC temperature gauge. I tried it on a rental car and it was coming out like 50 degrees at the same time for the rental. Never had any luck doing AC pressure readings but I did buy a gauge set. I hear if it has an expansion valve you can't get quite the right readings but then I also read that if the pressure isn't changing on the low side then you have something stuck or plugged and I'm not sure what that is.

At 85° I get a pressure of about 255 on the high side which appears from when I'm reading to be accurate but the low side is just 15. No matter how much Freon I put in there the low side pressure doesn't change and the high side pressure goes up and of course I have to evacuate that because it can't be too high I don't want to ruin the compressor. Also not sure what type of oil to put in I believe it's some kind of 46 oil but there's no real accurate information to confirm that there's a bunch of different oils. The compressor appears to be engaged fine. I did notice when I put fluid in you could see a little tiny bubbling from the high and low sides I tighten the needle valve down. This could indicate some kind of bad o-ring or needle valve that needs replaced I did put a new needle valve in one of them but I think it still has a little bubble where the needle valve is I think it also goes away though I guess when it gets agitated or something maybe they can bubble out a little I'm not sure. But this could indicate a separate problem I think regardless of the needle valve when you put 5 lb in there the pressure still on the left side never goes up above 15. So like I say two different advice that I saw on forums were that something is sticking cuz it should go up between 30 and 50 psi but then a contradictory for him said that because it might have an expansion fitting that it never will fluctuate or something but it just seems too low for me.

I can't find an AC place that will even look at it because it took camper and a diesel pusher. Maybe 63°is a normal reading with the compressor way in the back. But I really have no information on the routing or any of this for this it would be great to get a diagram of how it's routed and how many pounds it would take I mean I'm guessing it's about four to five pounds somebody said on some forum somewhere. It is r134a system.

This is a 2006 Monaco executive with a 525 horsepower isx15 Cummins engine that was supposedly upgraded to 600 HP on a Roadmaster
chassis.

Sorry for the long post but at least it's a full explanation hopefully. Not sure how to add pictures I don't see that option maybe I'm too new. Oh and most forms people don't post their solutions which drives me crazy so I promise I'll post a solution if I find one or what the final analysis was for example on the low pressure.

[RLS7201]

buystockinfun wrote:
Richard, thanks for the information on the compressor I didn't realize that that was the method to figure out the exact type of oil. Probably saw why some oil was added to begin with. Interestingly an RV dealer told me that they've seen systems take up to 10 pounds though I believe Doug said my system should only hold 4 lb.

As far as the dryer so you're saying I may need to replace the dryer. I'm supposed to use a wire to replace the dryer or are there fittings that need separated in the system evacuated and all of that? Or maybe you mean to do something with the expansion valve screen. It's my understanding that's all sealed and you would need to replace the expansion valve but is there a way to unclog it or do something with this screen with a small wire? Not sure I completely follow that.

When I say needle now I guess I mean is it a valve stem you know like the little valve stem thing inside of a air fill they look the same in the inner tube or your automotive tire as they do inside of those air conditioners the connector for the low and high side.

Thanks again so much

Let me try this again. The inlet of the expansion valve has a screen that some times gets clogged. After depleting the system, you take the hose fitting off the inlet side of the expansion valve. Look closely inside the valve and you will see a screen. If you see debris, remove the screen with a small bent, pointed wire and clean it. If there is debris in the system then the receiver/dryer will need too be changed, as it also filters the system. The receiver/dryer is a round tank with fittings on both sides, at the top. Remove fittings and loosen the clamp.
The needle that you mention is a schrader valve, very similar to a schrader valve in a tire.
As far as the refrigerant capacity of diesel MH systems, the location of the condenser is the major contributing item. If the condenser is in the rear, then the liquid line runs almost the full length of the MH. If in the front, then the liquid line is much shorter and less refrigerant is required.
To address the word "FREON". Freon is a DuPont trade mark and does not describe any chemistry. R12 & R22 are not FREON, they are dichlorodifluoromethane & difluoromonochloromethane. Where as 134A is Tetrafluoroethane. The word "refrigerant" covers the whole array of chemistry and is the word most normally used by trained technicians.

Richard

[dougrainer]

To your LP tank statement:B A 20 lb tank holds 5 gallons FULL. BUT you only fill to about 4.6 gallons liquid due to expansion and need for vapor. A 30 lb holds 7.5 gallons, but only fill to about 7.2 gallons. Fun Fact. Doug

[dougrainer]

There is NO screen you remove and clean. YEARS ago(35 to 45) GM and others had a orifice tube that had a screen that you could remove and clean/replace IF it caught debris caused by a failed component in the AC system. An expansion valve just opens and closes its orifice to meter the flow of coolant to get the heat removal done. You do NOT have to replace the dryer or tear the system apart. The fact you get 63 air shows the system is operating and you just need to do as I stated. Drain the system and install the 4 lbs and then see what happens. A dryer is usually replaced when you have had a catastropic opening of the sealed system or if the system has been opened to the air due to a drain and hole for some time. The dryer has a dessicant and needs replaced when that fails due to exposure to air. So, at this point you do not have to replace anything other than the 134a. Doug

PS ALL the components are replaceable

[buystockinfun]

Lol, I would think that to some extent just like in propane 5 gallon propane tank holds less propane then a 7.5 gallon. I would think the lines would increase the capacity somewhat but probably not double LOL so I get what you're saying. Without ripping the system apart on the highway basically I'm going to have to wait until I get home I guess. I still don't really understand the whole expansion valve thing and somebody was mentioning kind of screen and taking something and cleaning it I don't know if that means the system needs tore apart to do that. I know replacing the dryer and would involve tearing it apart as far as I could tell here the fittings are not removable as I see some places sell like green o-rings but it doesn't appear that this system is removable in terms of those fittings except for whatever that little valve is that looks like a tire valve. I have a feeling the dryer isn't removable either unless it's cut or something from what I can tell everything looks all soldered or welded or whatever you want to call it. I'm pretty sure I'm pretty primed to get ripped off at an AC shop if I'm not careful. On a side note I've never seen the compressor turn off while the engine was running I guess I should check to see if it turns off when the air conditioning knob is on off but it never turned off when I was filling it or whatever I guess maybe because of the pressure on the low side is what it is I don't know so there's a few things here that I don't totally understand. Is there anything I can do with that screen with the closed system? It almost sounded like I could but I don't know then I still have to find the stuff. Thxs

[Gjac]

rgatijnet1 wrote:
I think the needle is actually called a schrader valve.

When you say you see bubbles coming out of the Schrader valve that could be where your leak is coming from. You can tighten that valve with a tool. Some valve caps have that tool built in the top of the cap, either way these are $2 or less.

[dougrainer]

The LARGEST Poundage of a Diesel Motorhome built prior to 2016 is 5.5 lbs. YOURS(Roadmaster) is 4 lbs. The range is 2.0 lbs to that 5.5 lbs. One of the BIG myths of Diesel Motorhomes is that the LENGTH(38 to 45 foot) MUST use double to triple the POUNDS of coolant. NOT SO. I have Multiple RV and Automotive AC training and they state in that training that the Physics of Gas/Liquid does not really increase the amount of coolant for 45 foot runs. This is why that RV dealer(IDIOT) stated 10 lbs. Doug

[rgatijnet1]

I think the needle is actually called a schrader valve.

[buystockinfun]

Richard, thanks for the information on the compressor I didn't realize that that was the method to figure out the exact type of oil. Probably saw why some oil was added to begin with. Interestingly an RV dealer told me that they've seen systems take up to 10 pounds though I believe Doug said my system should only hold 4 lb.

As far as the dryer so you're saying I may need to replace the dryer. I'm supposed to use a wire to replace the dryer or are there fittings that need separated in the system evacuated and all of that? Or maybe you mean to do something with the expansion valve screen. It's my understanding that's all sealed and you would need to replace the expansion valve but is there a way to unclog it or do something with this screen with a small wire? Not sure I completely follow that.

When I say needle now I guess I mean is it a valve stem you know like the little valve stem thing inside of a air fill they look the same in the inner tube or your automotive tire as they do inside of those air conditioners the connector for the low and high side.

Thanks again so much

[buystockinfun]

rgatijnet1,

Looks like you and Doug are discussing the same thing I will definitely use this in my initial troubleshooting beyond what I have already done. Thanks so much

[buystockinfun]

When the person use the evacuation stuff they blew out a bunch of oil this green stuff replacing the needle so that's why it ended up getting oil in it.

So I'm gripping the heater core line in order to restrict the flow so it's not introducing the heat into the system I gather.

I hope I didn't use the word Freon but I suspect I probably did I do know the difference but it sure was easier to say than r134a LOL.

In the short term I'm going to try to do some of the methods described in a couple of posts and then I think eventually I'm going to evacuate it and do a vacuum test etc.. if I can find a shop that will actually do it that would be fine.

Thanks for the information Doug

[dougrainer]

1. YOU NEVER ADD OIL TO A SYSTEM. PERIOD
2. You only add any oil if you have had a catastrophic 134a coolant leak that blows out some oil.
3. As you probably know you have 134a not Freon.
4. To correctly test a Diesel motorhome Dash AC you must drive at 60 mph with the system on Max AC with a digital thermometer in one of the Passenger side AC outlet vents.
5. Also, you need to make sure the Condensor Fan IS running which it probably is since you get that 63 degree air.
6. Your year model holds 4.0 lbs of 134a.
7. Your BEST bet at this point is to remove the existing 134a and then install 4.0 lbs 134a, as you CANNOT be sure of the current charge
8. TOO MUCH 134a will cause cooling loss just as much as to little
9. At temps 95 or below at hiway speed, you best output will be in the 50 to 55 degree range.
10. To eliminate a possible hot water coolant valve leak take needle nose vise grips and clamp off the 2 coolant lines going to the Heater core. Note the best possible low temp after installing the correct amount of 134a and then see if that temp goes UP after removing the vise grips. Doug

[rgatijnet1]

Look for hot water that is leaking past the heater temperature control valve and mixing with the cold air from your AC system. There are usually a couple of 5/8" black hoses running in to and out of the same air box where your Ac evaporator coil is located. It is very common for these valves to leak and effect your AC output temperature.

[RLS7201]

Your problem could possibly be a restricted screen in the inlet of the expansion valve. A high side restriction would cause your issue. If you have a restricted screen, change the receiver/dryer also. Use a very small hooked wire to remove it. My ol Bounder will have a discharge temperature of about 48° on a 85° day, with high humidity.
Could you explain what you are calling a needle valve. None of the components in an AC unit are called a needle valve, that I'm aware of.
Look at your compressor for a brand name and model #. Then go to a parts store and have them sell you the proper viscosity oil for that brand and model.


Richard

[Y-Guy]

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