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Author Topic: AC gets warmer the faster I drive.  (Read 783 times)

Mark Beavin

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AC gets warmer the faster I drive.
« on: June 10, 2019, 03:44:33 PM »
My 30' Monterey ac system has a new condenser, dryer, Put a fan shroud on conderser and I cleaned the expansion valve as the screen was plugged. Yesterday it was like94 degrees when I left the track and the dash AC was putting out 53 degree air with the fan on high at idle. When I cruise at 60 mph and 2000 rpm the temp raised to 64 degrees and outside temp was about 97 when I got home 3 hours later. I have a charge of about 3.75 lbs. I've tried more charge but does not cool as well at idle and as soon as I got off the freeway and drove slower on surface streets the temp dropped to 57 on a drive of 5 miles. Going to check pressures today at 2000 rpm, should be 102 here. What should I look for?
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Fred Brooks

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Re: AC gets warmer the faster I drive.
« Reply #1 on: June 10, 2019, 04:02:23 PM »
   Hey Mark,
 Not really sure what is going on, The common denominator to your situation would be the air flow thru the condenser. Better air flow equals more heat dissipation equals lower hi-side pressure equals cooler evaporator temperature. Perhaps at 60 mph, you have changed the air flow dynamics thru the condenser with whatever you added? You stated the expansion valve was plugged at the screen. What kind of debris? If it is plugged again your gauges will be high on the high side and low on the low side. Hope this helps,
   Fred
 
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6
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Mike Shumack

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Re: AC gets warmer the faster I drive.
« Reply #2 on: June 10, 2019, 06:03:43 PM »
Could be that your expansion valve is freezing up because the system is low on charge. What pressures are you seeing on the high and low sides at 1500 rpm?
Another possibility is that the high side is going too high (at 2000 rpm) the "high pressure cut out" is disengaging the compressor clutch.

UPDATE:
I found a schematic for the Beaver Dash AC - looks to be good for 1997-2001 (maybe other years).
It shows that there is a "Trinary Switch" in the circuit. This is used to cut out the AC Compressor if the refrigerant pressure is too high or too low.

So putting a set of gauges on the coach is really necessary to continue troubleshooting. Your system pressure may be going to low at higher rpm because it is undercharged - or too high due to poor air flow through the condenser, etc..

Does your coach have the AC condenser mounted on the rear radiator or up front next to the generator with its own fan?
« Last Edit: June 10, 2019, 11:54:42 PM by Mike Shumack »
- Mike

'05 Beaver Patriot Thunder 525, Vicksburg, CAT C13, Allison 4000MH, HydraLift
Orlando, FL
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Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #3 on: June 11, 2019, 01:40:18 PM »
Mike, thanks for all your help, When I started this project the first thing I changed was the hi/lo switch cause it was leaking oil. The expansion valve I could not cross over so I looked through pages of valves to find one that looked like mine and it was for a Honda, mistake # 1, orifice was way to small for this system so I cleaned the old one, tiny screen was plugged. I replaced the condenser, also plugged and the dryer and got it to start cooling. A buddy of mine has a 6000.00 snap-0n ac charge station at a shop he runs. The schematic you show is spot on and my condenser is in the front with a fan. The fan was wired as a sucker fan, made no sense to me as it would be fighting any incoming air when going down the road so I switched wires and now it is a pusher fan. Also the 16" fan on a 22" condenser made no sense to me so I got a universal fan shroud and mounted the fan to that to force more air through more surface of the condenser. My last pressures I took were 150 high side, 38 low at idle on a 85 degree day, got 53 degree air out on high fan. I hung a curtain behind the captain chairs to limit cooling area as I realize it will never cool the coach as a whole. I did try more Freon 134 but temps went up at idle so I let some out. I'm at about 3.8 lbs of Freon right now. Tomorrow will be 104 hear and will go to my buddy's and get it on the machine and see what the pressures are at 2000 rpm as that is where the problem lies. As soon as I get on city streets it cools better. Did I make a mistake with the shroud? Should the fan be stand alone and as a sucker? It was 92 degrees when I left the track Sunday, a 3 hour drive and at Idle it was pushing 54 degrees fan on high, once on the freeway at 2000 rpm temp kept rising to 64 as I got home, but once off the freeway, a five mile drive to home it was back down to 57 and it was 97 outside. Thanks again for your help, we will get it figured out eventually. And I did flush the evap and It was clean.
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Fred Brooks

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Re: AC gets warmer the faster I drive.
« Reply #4 on: June 11, 2019, 02:04:03 PM »
    Mark,
  My coach had an issue with the air conditioner hoses. I went thru the same issues and finally found that the hi-side hose coming from the compressor had blisters on the inside liner that had broken loose and plugged up the condenser and the dryer. I ran new a/c hoses, replaced the condenser with the newer serpentine configuration and the dryer. I cleaned the expansion valve and flushed the evaporator. That was 3 years ago and blows 52 degrees on "Max Air" all day long on the freeway or stop and go. What kind of debris did you find?
    Fred
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6
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Mike Shumack

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Re: AC gets warmer the faster I drive.
« Reply #5 on: June 11, 2019, 04:24:35 PM »
Mark, it sounds like your'e doing all the right things. I'm sure you will have this figured out soon.

You many want to start over - and recover all the refrigerant and pull a long vacuum (over night) to be sure there is no air or moisture in the system. Any air would reduce cooling ability and can lead to false readings on the AC gauges.

Looking at the attached AC chart (from the Beaver manual) - it seems that you are close to correct amount of refrigerant (note that the chart says these coaches are factory filled with 5.0 lbs of 134a. For the Patriot). Also note the high side pressure spec is calculated by taking the air temperature  1" away from the condenser and adding 40 degrees to it (i.e. so if 90 degrees at the condenser +40 = 130 then the high side pressure should be around 199 psi.).

Your well below that now - so I expect you are still undercharged.

I don't remember my pressures now on the coach, but I repaired my pickup truck AC last year, and the pressures were around 40 low, 200-210 high side at 95 degree ambient).


 
- Mike

'05 Beaver Patriot Thunder 525, Vicksburg, CAT C13, Allison 4000MH, HydraLift
Orlando, FL

Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #6 on: June 11, 2019, 05:15:40 PM »
Fred, you may be right, the material was a black gooey material.  How did you fish the hoses through the frame?
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Fred Brooks

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Re: AC gets warmer the faster I drive.
« Reply #7 on: June 12, 2019, 01:48:48 PM »
      Mark,
I did not run the hoses thru the frame because it is almost impossible. I put the coach up as high as the jacks would go and then installed 4 by 6 blocks at each end of the frame. I ran both hoses up over the rear suspension then down under the coach up behind the generator and propane tank and back by the frame and over to the condenser. I fabricated a new hose between the new dryer and the new condenser and a new hose between expansion valve and the dryer. I had a truck repair shop install the crimped #8 & #10 fittings on the hoses, evacuate and charge with fresh oil and R134. I don't recall the amount. The pressures was about 45 on the low side and 220 on the high @ 80 degrees. I also replaced the compressor which I forgot to mention. The hose replacement took about 7 hours and I used electrical conduit clamps to secure the hoses underneath every 18".
   One more thing you may want to check is to make sure the max air door at the evaporator is opening all the way. That door closes off the outside air intake and only recirculates the cab air.
   The refrigerant is the hottest as it leaves the compressor on the way to the condenser. That is where the hose is subject to blistering over years of cycles. Good luck!
   Fred
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6

Mike Shumack

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Re: AC gets warmer the faster I drive.
« Reply #8 on: June 13, 2019, 11:02:24 AM »
Fred knows his stuff. One thing he didn't mention (and I'm sure he did it) is that you need to be sure you have the proper amount of oil in the system when ever you replace parts or flush. On cars it is not an issue to replace a hose and not add any oil, but on these coaches with 80+ feet of hose going front to back, there is a certain amount of oil to add just from replacing the hoses and refrigerant. It's described in the attachment of my earlier post.

These systems hold a specific amount of refrigerant and oil, as you know. The hard part is knowing how much oil was lost ( how much to add back in) when you have a leak and your just "topping up" the system. Most of the "add-a-can-R134a" will have some oil in them. Maybe enough for what your doing, maybe not. It's even harder when you run and AC flush through the system or a component as you cant tell how much oil was flushed out.

So to make a long post shorter - if you change any components (evaporator, compressor, etc.) be sure to add some PAG oil too.
- Mike

'05 Beaver Patriot Thunder 525, Vicksburg, CAT C13, Allison 4000MH, HydraLift
Orlando, FL

Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #9 on: June 13, 2019, 01:46:55 PM »
Mike and Fred,
  Spent the day working on this problem. Started by sucking down the system. Took out 2.42 lbs of Freon, drew a vacuum and put 3 lbs in and got about 200/ 40 at idle and at 2000 rpm the high side would hit 245 and cycle out the clutch and the low would stay about the same. A friend of my in Phoenix I was passing info to said the expansion valve was not opening right. My old valve is a Parker # 134-106 and nobody seems to have a cross for it. I found one that had all the same fittings but was listed for a Honda car. We sucked it back down, installed the new one and put 3 lbs back in to test. Now as the RPMs go up the low side would come down like it should but the high side would hit the limiter again so I started taking Freon out 1/4 # at a time. Got down to 1.5 lbs and added in 2.5OZ and end up with readings of 225 high and 30 low steady at 2000 rpm with out the high side cycling out. This is at 104 degrees outside air and only getting 68 inside. I'm beyond frustrated. Is the Honda valve not the right valve? Seems like to little freon for a 30' motorhome. Is the high limit switch not the right one cutting out at 245? I do have a new compressor for it but since there are no leaks and the old one seems to be working I have not replaced it and yes we added more pag oil after I flushed the lines and the evaporator. What should be my next step?

Mark
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Mike Shumack

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Re: AC gets warmer the faster I drive.
« Reply #10 on: June 13, 2019, 02:36:07 PM »
Where is the Condenser located (on the radiator at back, or up front)?
If in the front be sure the electric fan mounted on it is working. If in the rear, is the hyd. fan speed high enough? You can try spraying a mist of water on the condenser to see if the pressure drops 20-30 psi (indicating you might have an air flow/cooling problem at the condenser).

You are right to be concerned about having the correct Expansion Valve. If the orifice in it is the incorrect size, you will be chasing your tail.
My notes say the the "Monaco Expansion Valve - is p/n S07010776" which is VCS PN 034-00029 or SCS 034-00029, which is this https://pdxrvwholesale.com/products/expansion-valve-034-00029  does that look like yours? You may be able to research this part and find the tech specs on it to see how it compares to the Honda one you bought/installed (if the same, then you don't need to do anything. If different you may want to get this one).


EDIT: Another wesite said an equivalent Expansion valve the a Murray 38872  - I dont know if that is corect or not. https://www.oreillyauto.com/detail/b/murray-climate-control-4379/air-conditioning-16770/expansion-valve-12430/1be055d7cf0d/murray-climate-control-expansion-valve/38872/4518053
« Last Edit: June 13, 2019, 02:53:40 PM by Mike Shumack »
- Mike

'05 Beaver Patriot Thunder 525, Vicksburg, CAT C13, Allison 4000MH, HydraLift
Orlando, FL
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Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #11 on: June 13, 2019, 02:44:52 PM »
Yes that is the one. Thanks
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Fred Brooks

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Re: AC gets warmer the faster I drive.
« Reply #12 on: June 13, 2019, 03:20:45 PM »
    Mark,
 First of all, I am not an authority on automotive air conditioning. However I have been dealing with it for 49 years and have seen various anomalies develop. Your coach should have a capacity of at least 5lbs of 134 refrigerant. Another way of checking how the system is operating is to check the temperature readings on the gauges across from the needle pointing at the pressure reading. Look at the "134A" scale printed on the gauge and it will tell you the correct temperature you should have at that component. I don't have my gauges with me while I am on vacation in Colorado but let me give you an educated guess as an example. If your pressure on the low side is 40psi the temperature at the inlet of the evaporator should be around 35 degrees. If the pressure on the high side is 225psi the temp at the inlet at the condenser should be 180 degrees? (wish I had my gauges to look at).
   It still sounds like you have an issue with the high side hose gumming up the works. Just got off the phone with you, solder on my friend!
  Blessings, Fred
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6
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Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #13 on: June 19, 2019, 02:26:55 PM »
Update!!  Got the new compressor in, replacing the high side line, the old one showed no signs at the ends of deterioration. Waiting for the new expansion valve. Hope this does the trick.
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP

Mark Beavin

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Re: AC gets warmer the faster I drive.
« Reply #14 on: June 27, 2019, 01:16:40 PM »
Well I went back to the old set up with a non shrouded fan and put back to a puller fan. Was 91 outside and got 62 degree air at Idle and went to 58 at 2000 rpm and not driving. The expansion valve for the Honda turned out to be a 1.5 ton just like the one Mike recommended so I did not change it again and now have a new spare that took a week to get. The air flow seemed to be a lot of my problem a I was having trouble getting the High side to come up till I took off the shroud and reversed the fan. Thanks for all you help Fred and Mike.
Mark Beavin  Judi Binderman
FMC 491464
1996 Beaver Monterey 30'
3126 Cat Diesel 250 HP