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Old 05-26-2020, 02:21 PM   #1
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Dash A/C performance - what to expect?

After we bought our '14 FR Georgetown last fall, I felt the dash (chassis) A/C wasn't very cold, so when it was in for inspection I asked our shop to check the system and recharge if necessary. If I recall correctly they added 1 lb of 134a (and dye, just in case).

It didn't really seem that much colder afterwards and after getting it out of storage this spring I'm still pretty underwhelmed.

Our old E450 chassis class C had dash air that could pretty much keep everyone comfortable on the road as long as you didn't start with a heat-soaked coach. We never had to run the genset and roof air while traveling. As far as I can see, there's no way this rig is gonna get anywhere close.

I realize our dash air in the F53 is not the same thing, but is this middling performance all I should be expecting?
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Old 05-26-2020, 03:08 PM   #2
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Given the size of the interior of the coach you are expecting a lot from what is really an automobile sized air conditioner. Have you checked your center vent temperature? It should be around 50 to 55 degrees depending on ambient temperature.
To help get our coach more comfortable while traveling, we put a collapsible curtain rod between the two opposing slides when closed with a thick curtain installed. This cuts down on the area requiring cooling, when on recirculate, allowing the air conditioner to cool more effectively.
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Old 05-26-2020, 03:21 PM   #3
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I agree about interior volume. I should have been more specific - the air flow at the dash vents doesn't feel especially cool (how's that for subjective?).

I have a small IR thermometer and will check the air at the registers next time I have it running just to see where we are. I am certainly no A/C tech but I do understand the principle that there should be a certain drop over ambient temp.
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Old 05-26-2020, 03:50 PM   #4
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On your Class C the A/C and heating system was designed into the chassis and provided by Ford. On a class A chassis Ford is not supplying any of the components under the dash. The coach manufacturer’s low bidder supplies those (IMO)inferior parts.
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Old 05-26-2020, 04:28 PM   #5
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I was told that a drop of 20 degrees from the outside temp as typical for a rear engine diesel. If you have a front engine, the run is shorter, so you might do better.

As mentioned previously, an IR thermometer can be had for $19.95 from Harbor Freight and maybe Home Depot. When I checked mine, I was surprised that it was actually colder than my hand sensed.
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Old 05-27-2020, 09:11 AM   #6
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It makes me sad to see the 20degF rule quoted so many times. This is of course referring to ambient air temp.....oh well.

I rebuilt my dash a/c system last year after a compressor failure. What you should have out of your dash vents is air cooling to ~45degF. A little higher is okay...but not much over 50deg.

These systems are hard to leak trace...I still have a small leak and just can't find it...and the 35ft of hose is difficult to trace as well. And of course with so much piping....freon level according to Denso (the OEM) is 3.8#'s. Adding 1lb isn't bad...but maybe needs more.

We also do like others when traveling...put up a curtain behind front seats to keep the front cool...and turn on genny and rooftop a/c's about an hour or so before stopping for the day.
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Old 05-27-2020, 11:52 AM   #7
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When we had our 31’ class A Thor ACE the dash a/c worked great. Even when traveling down south in the middle of summer after starting off the drive with the a/c on high, after a few minutes when DW and I cooled down, I would end up turning the fan on a lower setting because it was getting to cold. Of course that was just for the driver and passenger seat, not the whole coach, but I never had to run with the gen on.
Now, fast forward to our Fleetwood DP that cost 3 times as much, I can drive in the south during the winter with the a/c on high and still won’t cool us off. One of the vents is 10” from my leg (while wearing shorts) and my leg doesn’t get cold. Pretty bad that I have to run the gen so I can have the roof mounted a/c on even in the winter. I have had 2 different dealerships look at it and they both say that they get the 20 degree difference in the ambient temp so they can’t do anything about it.
As the saying goes, “they can put a man on the moon but they can’t make a dash a/c in a DP that cools”.
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Old 05-27-2020, 12:13 PM   #8
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If you're not satisfied at the end of May, you're going to hate July. Something is wrong, and adding a pound of freon is not going to help. Take it to a shop that knows AC and is willing to help you. Otherwise, run the gen and the roof air. That's what it's there for.
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Old 05-27-2020, 12:30 PM   #9
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Lets explore the 20-25 degree differential "rule" at the vent a bit deeper.... Specifically, with regard to the definition of "ambient air" temps?

Example 1: its 90F outside the coach and 80F inside, what is the coldest air temp expected from the dash vent?
Example 2: still 90F outside but now coach has cooled to 70F; coldest temp from vent is?
Example 3: outside temp is now 60F, inside coach temp is also 60F; coldest vent temp is?
Example 4: air temp in my house is 72F today, temp inside my refridge is 38F; temp inside the freezer part is 0F.

For the sake of discussion, lets stipulate that ambient air temp in the immediate area of the dash vents is constant, as stated in the examples.

How does the 20-25 degree rule apply to these 4 examples??????
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Old 05-27-2020, 12:35 PM   #10
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Quote:
Originally Posted by Old Scout View Post
Lets explore the 20-25 degree differential rule at the vent a bit deeper.... Specifically, with regard to the definition of "ambient air?"

Example 1: its 90F outside the coach and 80F inside, what is the coldest air temp expected from the dash vent?
Example 2: still 90F outside but now coach has cooled to 70F; coldest temp from vent is?
Example 3: outside temp is now 60F, inside coach temp is also 60F; coldest vent temp is?
Example 4: air temp in my house is 72F today, temp inside my refridge is 38F; temp inside the freezer part is 0F


How does the 20-25 degree rule apply to these 4 examples??????
In answer to scenarios #1-3....it doesn't....vent should be at 50degF.
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Old 05-27-2020, 12:42 PM   #11
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Quote:
Originally Posted by Dippytwo View Post
When we had our 31’ class A Thor ACE the dash a/c worked great. Even when traveling down south in the middle of summer after starting off the drive with the a/c on high, after a few minutes when DW and I cooled down, I would end up turning the fan on a lower setting because it was getting to cold. Of course that was just for the driver and passenger seat, not the whole coach, but I never had to run with the gen on.
Now, fast forward to our Fleetwood DP that cost 3 times as much, I can drive in the south during the winter with the a/c on high and still won’t cool us off. One of the vents is 10” from my leg (while wearing shorts) and my leg doesn’t get cold. Pretty bad that I have to run the gen so I can have the roof mounted a/c on even in the winter. I have had 2 different dealerships look at it and they both say that they get the 20 degree difference in the ambient temp so they can’t do anything about it.
As the saying goes, “they can put a man on the moon but they can’t make a dash a/c in a DP that cools”.
Sad...
You are in warranty and RV dealers are not that bright. Plus they don't want to spend time working on a system they probably won't get paid for.
I can tell you that my 38' Fleetwood DP with a Denso system is putting out 48degF air from the dash vents...and works great. I have followed the factory service manuals both from Freightliner on DTNAConnect and from the Denso RV manuals.
If it's 100degF outside...and coach cools to 80degF...that's the 20degrees rule. Not what comes out of the evaporator vent.
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Old 05-27-2020, 12:46 PM   #12
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Originally Posted by brucenem View Post
If you're not satisfied at the end of May, you're going to hate July. Something is wrong, and adding a pound of freon is not going to help. Take it to a shop that knows AC and is willing to help you. Otherwise, run the gen and the roof air. That's what it's there for.
Agree that something is wrong. As to running the rooftop units....well yes...they work well too. It doesn't hurt my feelings to put up that curtain and save a few gallons of diesel to the genset if the dash air will get the job done.
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Old 05-27-2020, 12:47 PM   #13
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Even example 4????? So 50F air is coming out of the vents in my fridge and freezer? HUUUUUUMMMMMM?
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Old 05-27-2020, 12:47 PM   #14
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sans #4
Quote:
Originally Posted by Old Scout View Post
Even example 4????? So 50F air is coming out of the vents in my fridge and freezer? HUUUUUUMMMMMM?
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