Dash A/C question

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Dash A/C question

May 25, 2017, 12:16:35 am

98 U-320 36'

This will be our first summer using our coach. We're coming from a smaller Sprinter based chassis where the dash A/C worked fine to cool the driver and passenger because the cab area was smaller with less volume.

How effective is the dash A/C in the 36 foot U-320 at cooling the driver and passenger when temps are in the mid 90s?

Is it common to need to run a roof A/C while driving down the road when temps are between 90-100?

Thanks,
Chris

Re: Dash A/C question

Reply #1 – May 25, 2017, 12:20:12 am

We run our generator at those temps,we close the bathroom door and run the front AC,plus the dash ac.

Re: Dash A/C question

Reply #2 – May 25, 2017, 12:38:48 am

And later models extended the roof a/c ducting further forward to increase cool air delivery to the front seats FT and others offer it as a retrofit, I can attest it is a great improvement

Re: Dash A/C question

Reply #3 – May 25, 2017, 12:45:04 am

Does your dash A/C work, does it cool?

Re: Dash A/C question

Reply #4 – May 25, 2017, 01:44:13 am

We have always had to run the Generator to power the A/C on trips to the South. Very frustrating. "Auto" A/C not enough to cool so we added some overhead fans. Am having my A/C checked before we leave on next trip, but the area is just too big to rely on "Auto" A/C alone.

Re: Dash A/C question

Reply #5 – May 25, 2017, 04:42:04 am

Mine works good,PO had installed a new compressor.

Re: Dash A/C question

Reply #6 – May 25, 2017, 06:16:39 am

Our dash air works very good and we have the modification where there is duct work that adds 4 vents to the front (great option) that Tim mentions.
John

Re: Dash A/C question

Reply #7 – May 25, 2017, 06:20:37 am

According to our PO records, a whooolllleee lot of money went into making the dash air work. But it doesn't work. Generator and rooftop air have worked fine for us while driving, even in 95 degree weather. Not throwing any money down that sinkhole.

Re: Dash A/C question

Reply #8 – May 25, 2017, 07:16:28 am

Our dash AC units are pretty simple,can you give more info.

Re: Dash A/C question

Reply #9 – May 25, 2017, 08:39:51 am

Quote from: Numbers – May 25, 2017, 12:16:35 am

98 U-320 36'
Is it common to need to run a roof A/C while driving down the road when temps are between 90-100?

Dash AC is all you need if you drive west in the morning and east in the afternoon.

Re: Dash A/C question

Reply #10 – May 25, 2017, 08:45:20 am

Quote from: John44 – May 25, 2017, 07:16:28 am

Our dash AC units are pretty simple,can you give more info.

While I do appreciate that very much, and I do believe you - time is the premium commodity here. Since we have a functioning solution for driving temps, a dash A/C feels like a convenience item that ranks lower than a slew of other more pressing weekend project checklist items.

Perhaps I can reach out at a later point when convenience items move their way to the top of the list?

Re: Dash A/C question

Reply #11 – May 25, 2017, 09:30:00 am

The reason a dash A/C doesn't work is because (sadly), somebody that knows what they are doing hasn't fixed it. Mine blows nice and cold, and since I usually drive alone, it's all I need when driving.

It really could cool more, and needs better ducting and vents.

I pondered about putting another air handler unit in the middle of the RV with another A/C coil and heater core....maybe one day, but probably not lol

Re: Dash A/C question

Reply #12 – May 25, 2017, 09:51:28 am

The dash air on my '99 according to Barry's information page is 22,000 btu. more than 50% more btu. than our roof air. With 40 deg. register temp. it cools the front without the roof up to the ambient 90 deg. point. at which time the front roof air get used also.

Re: Dash A/C question

Reply #13 – May 25, 2017, 10:10:45 am

Thank you all for the replies!

The coach is in a local heavy truck shop for service. Sounds like it's a good time to have them check the system to make sure it's charged, etc.

Chris

Re: Dash A/C question

Reply #14 – May 25, 2017, 10:59:16 am

I wrote about my repairs to my Dash A/C on these forums with pictures and explanations. They shouldn't be too hard to find.

My dash A/C worked when I bought my RV, but it was cycling and low on charge. I topped it off, but it still didn't work as well as I thought it should. It would still cycle the compressor and not freeze me out.

Then I had a high-side line blow that came across the engine valve cover. It blew, because it was not insulated and about 14inches away from the hot-side of the turbo. Over the years, the heat made the line brittle. I replaced the line (from the compressor to the condenser) and put foil insulation over it.

Because the system was open, I dug deeper and figured I'd replace the TXV (expansion valve) for $40, and replace the receiver/dryer. Glad I did, as there were some desiccant balls lodged in the existing TXV. I believe the TXV was probably working, it was just blocked. Flushed all the lines with acetone, then blew out with nitrogen. Vacuumed down for a while, and dumped plenty of r134a in it. Been working great ever since!

Re: Dash A/C question

Reply #15 – May 25, 2017, 02:47:24 pm

I just charged my AC, tightened the belt and it works great. In the 95 320 a couple fans are plenty to push the cool air.

Re: Dash A/C question

Reply #16 – May 25, 2017, 02:51:30 pm

Krush how much air flow do you get from the vents themselves. The ac is cold just not much fan output.

Re: Dash A/C question

Reply #17 – May 25, 2017, 03:01:57 pm

Some people hang a curtain rod behind the driver and passenger seats to semi seal off that area using a fine mesh material.
They claim it helps quite a bit. We haven't done that yet because pure has been working fine up to 90-95 deg. It does help if you don't have the sun coming in the front window also.

Re: Dash A/C question

Reply #18 – May 25, 2017, 03:50:16 pm

Sold lots of ftx coaches with the curtain behind the D & P seats. And drop bunks

Re: Dash A/C question

Reply #19 – May 25, 2017, 09:37:16 pm

Quote from: Caflashbob – May 25, 2017, 02:51:30 pm

Krush how much air flow do you get from the vents themselves. The ac is cold just not much fan output.

It blows pretty well on the driver. I just have a gut feeling it could cool more btu/hr if ti had more airflow over the coils.

Re: Dash A/C question

Reply #20 – May 25, 2017, 10:16:57 pm

The curtain works well and slows the air movement when you brake /accelerate. Cold air passes the warm air .

Re: Dash A/C question

Reply #21 – May 25, 2017, 11:47:46 pm

Quote from: krush – May 25, 2017, 09:37:16 pm

It blows pretty well on the driver. I just have a gut feeling it could cool more btu/hr if ti had more airflow over the coils.

You would get more sensible cooling capacity by increasing airflow system volumes. Up to the point that the air volumes raise the coil face velocities past 500 to 600 cfm/sqft of coil face size. At that point you blow the condensate off of the coil and into duct systems that have no drain systems. And make a dripping ductwork mess, mold and corrosion source, and poor humidity control. Air volumes per btuh system size are quite complex. Throw into this mix that unfiltered air on a vehicle ac system tends to degrade the evaporator coil performance due to dirt sticking to the wet coil. That's why they stink so much during cooling season start up. Pretty crappy system.

Re: Dash A/C question

Reply #22 – May 26, 2017, 12:05:54 am

I am thinking the vent distribution on pre 2000 foretravels is not the best. My coach blow cold but being low on the dash, the airflow from the drivers vents hit the steering wheel and is deflected before getting to my body. If near the top of the dash, like on newer coaches, it would probably be better.

Re: Dash A/C question

Reply #23 – May 26, 2017, 12:24:01 am

Quote from: jcus – May 26, 2017, 12:05:54 am

I am thinking the vent distribution on pre 2000 foretravels is not the best. My coaches blow cold but being low on the dash, the airflow from the drivers vents hit the steering wheel and is deflected before getting to my body. If near the top of the dash, like on newer coaches, it would probably be better.

Distribution is everything in the comfort realm, but if the "pretty committee" overrides, as it always does, you lose cause "pretty" moves them off the sales lot. Been that way forever, and I can't possibly see it changing in the future, as "pretty" is always in the driver's seat.

Re: Dash A/C question

Reply #24 – May 26, 2017, 09:09:06 am

I believe they have clear window film that can be applied to the windshield and has heat reflecting qualities like the tint does.

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