Good Sam Club Open Roads Forum: Class A Motorhomes: Dash AC not cold
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buystockinfun

California

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Posted: 07/26/21 08:18am Link  |  Quote  |  Print  |  Notify Moderator

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.

Y-Guy

Tri-Cities, WA

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Posted: 07/26/21 08:31am Link  |  Quote  |  Print  |  Notify Moderator

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RLS7201

Beautyful Downtown Gladstone, MO

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Posted: 07/26/21 09:35am Link  |  Quote  |  Print  |  Notify Moderator

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

* This post was edited 07/26/21 09:46am by RLS7201 *


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rgatijnet1

Florida

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Posted: 07/26/21 11:39am Link  |  Quote  |  Print  |  Notify Moderator

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.

dougrainer

Carrolton, Texas

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Posted: 07/26/21 04:27pm Link  |  Quote  |  Print  |  Notify Moderator

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

buystockinfun

California

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Posted: 07/26/21 04:58pm Link  |  Quote  |  Print  |  Notify Moderator

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

buystockinfun

California

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Posted: 07/26/21 05:00pm Link  |  Quote  |  Print  |  Notify Moderator

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

California

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Posted: 07/26/21 05:05pm Link  |  Quote  |  Print  |  Notify Moderator

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

rgatijnet1

Florida

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Posted: 07/26/21 05:12pm Link  |  Quote  |  Print  |  Notify Moderator

I think the needle is actually called a schrader valve.

dougrainer

Carrolton, Texas

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Posted: 07/26/21 07:06pm Link  |  Quote  |  Print  |  Notify Moderator

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

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