AC Dryer tank

[Yoaks5]

That's a good idea. I know my static pressures always read good. Both about the same as the outside temp. It's only after I start it that the low pressure drops. I could try changing the hoses on the manifold so the  pressures would read on the other gauge... see if that tells me anything. That would be great if that was the issue. I'd gladly throw my gauges away and buy a new set if that solved the problem 😁. 

[Yoaks5]

Hooked my gauges up and both high and low were the same right at the outside temp of 77 degrees. Switched the hoses on the gauges and started it up got the same readings as before. 5 psi low and 160 high @ 700 rmp. Switched the hoses back and hooked it up to my car (ac working fine on it) and got 30 low and 200 high so don't think there is any problem with the gauges. 

Any other ideas? 

On 6/3/2022 at 3:47 PM, Ivan K said:

Kevin, when I replaced my expansion valve, I got it from truckair.com, the one circled below, 1 1/2 ton.

I can't get truckair.com to open but I got most of my parts from ACParts.com and when I enter your part number it crosses to the same valve I have. But mine doesn't have the mounting holes. Mine is also 1.5 ton so I'm thinking it's correct. Maybe I got a bad one?

[Ivan K]

Kevin,  that website may not exist anymore, the snapshot was from 2016 when I worked on my AC. Sounds like you got a correct part.

But, I have to throw a wrench into the previous discussion about high side pressures. I dug out my old notes and then hooked gauges on mine this morning. Obviously, I did not go by the Monaco table back then because my pressures are much higher, working well and had been since 2016. I might have used someone's writeup that I will post and then some to get to decent low pressure. Unfortunatelly, I can't tell you how much freon is in because I had to recrimp a leaky fitting later on, after the initial fill, while the hose was still hooked up and just added more afterwards. I could have done better since I have a recovery machine but I probably was in a hurry to do that.

Anyways, at 83F by the condenser, I measure 30/240 when stabilized and about 45F at the dash while idling. 

[Yoaks5]

17 hours ago, Ivan K said:

Kevin,  that website may not exist anymore, the snapshot was from 2016 when I worked on my AC. Sounds like you got a correct part.

But, I have to throw a wrench into the previous discussion about high side pressures. I dug out my old notes and then hooked gauges on mine this morning. Obviously, I did not go by the Monaco table back then because my pressures are much higher, working well and had been since 2016. I might have used someone's writeup that I will post and then some to get to decent low pressure. Unfortunatelly, I can't tell you how much freon is in because I had to recrimp a leaky fitting later on, after the initial fill, while the hose was still hooked up and just added more afterwards. I could have done better since I have a recovery machine but I probably was in a hurry to do that.

Anyways, at 83F by the condenser, I measure 30/240 when stabilized and about 45F at the dash while idling. 

Ivan I really appreciate your help! 

So based on this I may need to add more freon. When I added the last pound going from 4 lb to 5lb it didn't change the pressure any. I would have thought it would have changed some. It did while I was adding freon, low side went up to 50psi  but went down once it stopped adding. 

I'm not sure what to do at this point. Maybe try adding a bit more to see what happens?

[Guest Ray Davis]

I believe you have something else wrong, 5 lbs should be more than enough rrfrigerant.   The pressures you have don't seem dangerous to me, but they for sure are not correct and adding more is not bringing them up as expected.  Someone with real understanding of refrigeration systems will hopefully chime in.  I'm begining to wonder if there may be a problem with your compressor, can it even develop more pressure?                                Then there is the expansion valve, I believe it has the responsibility of regulating the flow of freon causing the high pressure and low pressure to be in their proper range otherwise the freon would just go round and round with no cooling.    So, it's most likely not a restriction, it seems to me that would likely cause high pressures.

Enough rambling, I'll stop,,,, for now. LOL

BTW when you are adding freon you are reading higher pressure from the can, its pressure must be higher than the system pressure for freon to flow into the system.  Normally as the system nears full and the can has cooled from the effect of freon flowing from the can the cans pressure decreases, pressures equalize and the can may be heated some by hot air from the radiator to bring its pressure up.

Edited June 7, 2022 by Ray Davis

[Ivan K]

Personally, I would add more and expect the working pressures to increase but I can recover the freon if I need to revert so a bit different situation. Are you certain there's no leak? Can't tell just by static pressures.

[Paul J A]

Anyone use some dye to help locate a leak?

[Guest Ray Davis]

1 hour ago, Ivan K said:

Personally, I would add more and expect the working pressures to increase but I can recover the freon if I need to revert so a bit different situation. Are you certain there's no leak? Can't tell just by static pressures.

Yeah I don't think it would hurt to try adding some more, but so far adding hasn't done much.  Ivan mentioning recovering the freon reminded me of a guy I knew that came to help me repair my home HVAC. We didn't have a recovery machine so he used a tub to sit an empty 20# freon container in, we filled the tub with ice & water maybe salt too ( CRS ).  The cold sucked practically all the freon out.  Later we reversed the process using hot water, again practically all of the freon went back in.              I think the practice was fairly common back then, might get you jail time now.

[Dr4Film]

6 hours ago, Paul A. said:

Anyone use some dye to help locate a leak?

Just before leaving for New Hampshire, I had the dash AC system evacuated and recharged with dye to see if there might be a leak. The system only had 2.5 lbs of freon so it was definitely low. However, once the process was completed the service tech noted that he wasn't getting the pressures that he expected. So once I return back to Florida for the winter, I plan to have a new expansion valve and dryer replaced. The tech will also look for possible leaks too and if needed possibly a new compressor.

[Yoaks5]

21 hours ago, Ivan K said:

Personally, I would add more and expect the working pressures to increase but I can recover the freon if I need to revert so a bit different situation. Are you certain there's no leak? Can't tell just by static pressures.

Certain there is no leak... no. I did vacuum the system down to -30 and it ended up sitting there for over 2 days before I was able to work on it again. And when I hooked the gauges back up it was still -30. So thought that was good and added freon. 

I'll add some die and look for leaks. 

20 hours ago, Paul A. said:

Anyone use some dye to help locate a leak?

Ya I did to initially find my leak. Works pretty well. Added die then closed shop doors and windows, turned off the lights and used a uv Flashlight and glasses to see leaks. I'll try this again maybe I can find a different color die.

[Dr4Film]

Holding a vacuum versus being able to hold and sustain the high pressures of the AC system are two different situations. Big difference between vacuum and pressure.

[Yoaks5]

20 hours ago, Ray Davis said:

Yeah I don't think it would hurt to try adding some more, but so far adding hasn't done much.  Ivan mentioning recovering the freon reminded me of a guy I knew that came to help me repair my home HVAC. We didn't have a recovery machine so he used a tub to sit an empty 20# freon container in, we filled the tub with ice & water maybe salt too ( CRS ).  The cold sucked practically all the freon out.  Later we reversed the process using hot water, again practically all of the freon went back in.              I think the practice was fairly common back then, might get you jail time now.

Interesting... maybe I'll try that if I end up adding more freon and want to get some back out. First I'll look for leaks. 

[Yoaks5]

Added the die ran the motor with ac on max for 30 minute looking for a leak but didn't find any. Added another can of freon no change. When unhooking the gauges noticed a slight leak in the low side Schrader valve. Tightened it up. Thinking maybe I was not getting all the freon in the system due to the leak I added another 8 Oz and no change. Still at 2psi low and 150 high. 75 degrees outside. Seams that I can't build pressure over that.

Does anyone know if I remove the ceilings in the storage bays can I see the ac hoses? Thinking maybe I have a leak in a hose that I can't see. 

Other than that not sure... assume the compressor is working since I'm getting 45 degree temps at the register. 

We're going on a trip next week so I'm thinking I'll just use it like normal but keep an eye on the dash register temp and if it starts going up I'll just shut it off. We normally run with the genset on and run the overhead ac anyway. Any issue with this? 

[Ivan K]

Pretty strange situation, I lost track of how much freon you already put in. How about a potential evaporator leak? Could you see it? I could not until the dye gets washed out through the drip hose. Sniffers got reasonably cheap these days, maybe something to invest in for the unreachable areas there and in the basement. Just don't let the wind blow it away if you try that. I run the gen and rooftop or two in the summer too, don't want to cook the dogs back there.

[georgecederholm]

21 minutes ago, Yoaks5 said:

Added the die ran the motor with ac on max for 30 minute looking for a leak but didn't find any. Added another can of freon no change. When unhooking the gauges noticed a slight leak in the low side Schrader valve. Tightened it up. Thinking maybe I was not getting all the freon in the system due to the leak I added another 8 Oz and no change. Still at 2psi low and 150 high. 75 degrees outside. Seams that I can't build pressure over that.

Does anyone know if I remove the ceilings in the storage bays can I see the ac hoses? Thinking maybe I have a leak in a hose that I can't see. 

Other than that not sure... assume the compressor is working since I'm getting 45 degree temps at the register. 

We're going on a trip next week so I'm thinking I'll just use it like normal but keep an eye on the dash register temp and if it starts going up I'll just shut it off. We normally run with the genset on and run the overhead ac anyway. Any issue with this? 

Kevin,

I know enough about these systems to know I don’t know enough to give much more advice, but I will say this. If you start losing dash register cooling, I would do more than just turn it off. I’d make darn sure that the compressor clutch had disengaged. In fact, on mine, I’ve disconnected the electrical pigtail at the compressor to help ensure it doesn’t engage and damage the compressor.

27 minutes ago, Yoaks5 said:

Does anyone know if I remove the ceilings in the storage bays can I see the ac hoses? Thinking maybe I have a leak in a hose that I can't see. 

Kevin,

Sorry, I missed this part. Yes, you can remove the ceiling panels in the storage bays and get access, but it’ll be a real rats nest with lots of stuff encased in wire loom and zip tied together. For the non-storage bays, you’ve got to do the best you can from an adjacent location. I have three of these, fuel tank forward, then Aqua-Hot and holding tanks aft. The further aft, the more “stuff” (not everything goes all the way forward).

After spending time in mine trying to run a Romex wire, I can certainly understand why most people who have had to run new anything generally do it through a conduit attached to the underbelly of the bays.

[Yoaks5]

1 hour ago, Ivan K said:

Pretty strange situation, I lost track of how much freon you already put in. How about a potential evaporator leak? Could you see it? I could not until the dye gets washed out through the drip hose. Sniffers got reasonably cheap these days, maybe something to invest in for the unreachable areas there and in the basement. Just don't let the wind blow it away if you try that. I run the gen and rooftop or two in the summer too, don't want to cook the dogs back there.

I've put about 6lbs in total. But not sure how much leaked out of the Schrader valve that was leaking or how much didn't go in! I'm also losing a little every time I hook the gauges up since some gets left in the hoses. I bet I've hooked them up a dozen times now. I can't see the inside the evaporator there is a cover over it. I'll keep an eye on the drip hose though. I'll look into a sniffer once I get back from our trip. Thanks Ivan! 

[Ivan K]

Have a good trip Kevin!

[Yoaks5]

2 hours ago, georgecederholm said:

Kevin,

I know enough about these systems to know I don’t know enough to give much more advice, but I will say this. If you start losing dash register cooling, I would do more than just turn it off. I’d make darn sure that the compressor clutch had disengaged. In fact, on mine, I’ve disconnected the electrical pigtail at the compressor to help ensure it doesn’t engage and damage the compressor.

Kevin,

Sorry, I missed this part. Yes, you can remove the ceiling panels in the storage bays and get access, but it’ll be a real rats nest with lots of stuff encased in wire loom and zip tied together. For the non-storage bays, you’ve got to do the best you can from an adjacent location. I have three of these, fuel tank forward, then Aqua-Hot and holding tanks aft. The further aft, the more “stuff” (not everything goes all the way forward).

After spending time in mine trying to run a Romex wire, I can certainly understand why most people who have had to run new anything generally do it through a conduit attached to the underbelly of the bays.

Thanks George! If it starts acting up in any way I'll just unplug the compressor. I don't want to take any chances. Don't think I'll really need the dash air anyway. 

I'm hoping once I take the ceiling down I'll check with the uv light and see a big area of die if I have a leak in the hose (although that's not the way it normally works for me). At this point that seams to make the most sense. I did have the hoses rub a spot threw back by the motor that I repaired. So thinking I may have the same thing in the other 60 foot of hoses I can't see. 

Edited June 9, 2022 by Yoaks5
Spelling

[vanwill52]

Ivan, I've never had to touch my coach's AC.  It has always worked--ten years and about 90k miles.  Just turned over 200K on last trip.  So, I have NO coach AC experience, but on the six cars I've worked on, I've replaced compressors, condensers, driers, high and low pressure switches...everything but an evaporator (UGH!)  On all  that I've worked on, anything less than about 5 PSI would disengage the compressor.  Isn't that normal?

[Ivan K]

57 minutes ago, vanwill52 said:

Ivan, I've never had to touch my coach's AC.  It has always worked--ten years and about 90k miles.  Just turned over 200K on last trip.  So, I have NO coach AC experience, but on the six cars I've worked on, I've replaced compressors, condensers, driers, high and low pressure switches...everything but an evaporator (UGH!)  On all  that I've worked on, anything less than about 5 PSI would disengage the compressor.  Isn't that normal?

Van, agree, UGH on the evaporator. I am refusing to do them on the cars that that are held together with plastic clips as most are these days. As for the low pressure switch, I have only seen it fail in an open state so I assume that it sees enough pressure in it's location.

[wamcneil]

On 6/7/2022 at 7:11 AM, Yoaks5 said:

When I added the last pound going from 4 lb to 5lb it didn't change the pressure any. I would have thought it would have changed some. It did while I was adding freon, low side went up to 50psi  but went down once it stopped adding. 

 

Within limits, adding freon really shouldn't change the pressure much. It's driven by boiling point of the refrigerant, not like adding air to your tires. Once you've got some minimum amount of refrigerant in the system, the pressures should pretty much plateau until you have too much refrigerant in the system. The low-side pressure rises while you're actively adding refrigerant because you're upsetting the equilibrium and adding more volume of refrigerant behind the compressor. 

The compressor sends high pressure gas through the condenser, from which it emerges as mostly liquid. That liquid accumulates in the reservoir (receiver/filter/dryer) and high pressure lines downstream as the liquid is waiting to be pulled from the bottom of the RFD and metered through the expansion valve. So until the RFD and lines downstream of the condenser are full of liquid, the pressures should stay mostly the same.

Have you considered posting your issue on a refrigeration forum? In the past I had good results searching and asking the community at autoacforum.com (was formerly ackitsforum.com)

Cheers,

Walter

Edited June 9, 2022 by wamcneil

[Guest Ray Davis]

I was pecking around on the net and found some info addressing both pressures being low.  These 3 things caught my attention,  especially the loose belt. I can see a loose belt as a possibility, and easily overlooked.

belt loose or sliping

expansion valve

evaporator coil dirty

Edited June 9, 2022 by Ray Davis

[Yoaks5]

15 hours ago, wamcneil said:

Within limits, adding freon really shouldn't change the pressure much. It's driven by boiling point of the refrigerant, not like adding air to your tires. Once you've got some minimum amount of refrigerant in the system, the pressures should pretty much plateau until you have too much refrigerant in the system. The low-side pressure rises while you're actively adding refrigerant because you're upsetting the equilibrium and adding more volume of refrigerant behind the compressor. 

The compressor sends high pressure gas through the condenser, from which it emerges as mostly liquid. That liquid accumulates in the reservoir (receiver/filter/dryer) and high pressure lines downstream as the liquid is waiting to be pulled from the bottom of the RFD and metered through the expansion valve. So until the RFD and lines downstream of the condenser are full of liquid, the pressures should stay mostly the same.

Have you considered posting your issue on a refrigeration forum? In the past I had good results searching and asking the community at autoacforum.com (was formerly ackitsforum.com)

Cheers,

Walter

Thanks Walter... I'll do some snooping in this forum when I get back. 

14 hours ago, Ray Davis said:

I was pecking around on the net and found some info addressing both pressures being low.  These 3 things caught my attention,  especially the loose belt. I can see a loose belt as a possibility, and easily overlooked.

belt loose or sliping

expansion valve

evaporator coil dirty

Thanks Ray! I only have 1 belt and it also is hooked to the alternator which seams to be working good. Could be I got a bad expansion valve (it's new) or the evaporator is dirty and I couldn't tell. It'll be interesting to see what happens on the trip next week. I'll be driving 8 hours total.