Dash Air servicing?

Topic: Dash Air servicing? (Read 1238 times) previous topic - next topic

Dash Air servicing?

May 30, 2014, 11:08:43 pm

I finally found and fixed the vacuum generator system so I could control the dash air vents. I had been told by FOT that I needed a new $265 vacuum generator a few years ago, and I passed on that as not being that necessary for my comfort. (The switch was clicking, and they told me that meant I needed a new one.) Anyway, looking closely into the system myself, I found the cause of the clicking to be a 75 cent length of vacuum hose which I replaced and it now works fine.

So, my dash A/C now needs to be recharged. Is this as simple as an auto system on my post-1994 vehicles that have R134A? If I search the engine compartment, will I find standard fittings for checking pressure and adding the refrigerant? Or is this going to be more complex than on a car? Thanks for any help.

Re: Dash Air servicing?

Reply #1 – May 30, 2014, 11:25:21 pm

Same as any R134a auto with same fittings on hi & lo hoses near compressor. Just most do not have sight glass anymore. For a simplistic re-charge with a systems that has some pressure, we have added Walmart r134a with short hose to low side. We run compressor and put can in hot water to keep pressure in can higher than low side.

If system is way too low the low pressure switch on low hose near compressor needs to be jumped so compressor will run. But if system is too low maybe there is a significant leak that needs to be found with dye in system and black light at night.

Run dash fan on high and sense when cold air comes out. Using a gauge set is better.

Re: Dash Air servicing?

Reply #2 – May 30, 2014, 11:45:40 pm

Thanks Barry. The one thing I forgot to do before heading out. It will probably keep til I get back home then, as I do have a guage kit there.

Re: Dash Air servicing?

Reply #3 – May 30, 2014, 11:58:01 pm

What I do to make sure I don't over charge the system is place a thermometer in the dash vent that is closest to the evaporator. As I add R134A I can see the temperature drop. I stop adding when I see that the temperature seems to level off. I use a electronic thermometer with the bulb on a cable and place the display in the front windshield so I can see it from outside while adding the R134A. I have a Grand Villa where the ports are up front. Not sure, but I believe the port for the bus style coaches are in the back so might need a wireless remote thermometer or just a helper.

Re: Dash Air servicing?

Reply #4 – May 31, 2014, 10:00:25 am

A word of caution here. Air Conditioning systems can seriously injure or kill you!

Now, I already know there are thousands of anecdotal stories and firsthand experiences of people who recharge their systems without proper tools or understanding but the one time something goes wrong can erase a lifetime of good luck.

134A systems operate at pressures of 350# & up. A stream of liquid or gaseous refrigerant at those pressures through a defective line or hose or in an overcharged system will put out your eye(s) and/or cause serious damage to skin.

The 134A molecules are smaller than the old R-12 molecules on older equipment. They will migrate through hoses and fittings over time, causing a low charge situation. Lots of folks use methods similar to those mentioned in this thread to add refrigerant. This can work but sometimes does not, with catastrophic results. What are the risks verses rewards?

The only way to correctly charge any closed, non-receiver equipped system is to recover whatever charge is left in the system, evacuate the system to at least 400 microns. and weigh in the correct charge according to the manufactures specs. You CAN add charge to a partially charged system by measuring the ambient air temp, the supply air temp, and the superheat (or sub-cooling depending on the manufacturer) and comparing them to the manufacturers pressure-temperature charging chart.

Folks on this forum have spent thousands, and in some cases hundreds of thousands of dollars on equipment. Please don't cut short your enjoyment of the equipment by skimping on repairs on dangerous systems. Either spend some time learning the correct procedures or pay a knowledgeable mechanic to repair your AC system.

FYI, i have owned an HVAC firm for 40 years and am licensed for installation and repair of stationary, transport and
marine systems.

Lastly, I am NOT trying to be difficult, insult anyone, tic anyone off, or otherwise open any cans of worms.

I JUST WANT EVERYONE SAFE AND HEALTHY TO ENJOY OUR TOYS!

Best Regards!

TOM

Re: Dash Air servicing?

Reply #5 – May 31, 2014, 11:32:22 am

Tom, Glad you said, I should have.
Gary B

Re: Dash Air servicing?

Reply #6 – May 31, 2014, 12:34:58 pm

Quote from: Dave M – May 31, 2014, 03:53:45 am

Seems that if you have to add the R134A, just maybe you have a leak and having it repaired is also an option ? Something like a leaking tire you have to keep pumping up ?

Would you repair/replace a tire that lost 20 psi over a few years? Perhaps this will need more than just a little R134a, but adding some, properly, is a sensible first step.

Re: Dash Air servicing?

Reply #7 – May 31, 2014, 12:43:30 pm

BTW, the pressures in the hydraulic slide system that I had apart FAR exceed 350 PSI and could easily cut off fingers if care is not exercised. But with that said, it still isn't rocket science. I agree that any work on most of our systems requires a bit of education and a large measure of caution.

Re: Dash Air servicing?

Reply #8 – June 03, 2014, 10:24:23 pm

While coming back from Missoula yesterday I noticed that the dash air was not very cold.

Brad - I am getting tired of following your repair experiences.

Do I need to get a a/c gauge set-up?

Re: Dash Air servicing?

Reply #9 – June 04, 2014, 12:27:11 am

Quote from: Carol & Scott – June 03, 2014, 10:24:23 pm

While coming back from Missoula yesterday I noticed that the dash air was not very cold.

Brad - I am getting tired of following your repair experiences. Do I need to get a a/c gauge set-up?

LOL. I will just plug in my handy recharge kit with gauge and see if it will take any more without going up too high. I normally use the generator and A/Cs and leave the dash off, but I thought I'd try to see if this was easy. Likely not, but worth a little effort. I don't have a trusted A/C service place, but I don't want to get too deep into it. The Roof A/Cs work great! (I am certainly enjoying having my slide out this trip...I'm in Salem, OR...and have herd nary a peep/creak out of it in a week. So.Much.Room!

Re: Dash Air servicing?

Reply #10 – June 04, 2014, 10:38:03 am

I'll get by NAPA to find a recharge kit. I presume the service port is in the engine compartment near the a/c compressor. We Like Salem, Or. Have a nephew and family live there. Glad you are enjoying you new room. Ours appears to be working well and staying out. No creep.

Re: Dash Air servicing?

Reply #11 – June 04, 2014, 11:30:51 am

You should find the service ports on (or near) the engine to be the standard R143a ports.

As I believe has already been mentioned, an overcharge of R134a decreases cooling performance. Therefore, the best method for charging includes using a thermometer to carefully monitor the temperature of the air at the dash vents. Working from memory, since (thankfully) I haven't needed to add refrigerant to any vehicle for quite some time, I believe the idle speed should be around 1100 RPM, the selector set to "recirculate" and the dash blower speed set to high.

Basic Charging Procedures

Re: Dash Air servicing?

Reply #12 – July 27, 2014, 01:39:26 pm

Wondering if anyone has had favorable experience with dash-air repair/service anywhere between Winslow Arizona and Denver, CO? I've called more than a few places that advertise "Auto Air Service" but none were interested in taking on a DP system. (Insert heavy sigh....) Familiarity with FT could be a big plus, too, as I suspect component locations vary by manufacturer. Thanks in advance!!

Re: Dash Air servicing?

Reply #13 – July 27, 2014, 02:20:06 pm

I had the A/C worked on by MOT last year when we were there for service, and it worked about as long as it took to get out of Texas. Fast forward I had the system evacuated which held a vacuum for 15 minutes. Tech added 6lbs of freon and I had A/C again. But only for 1/2hour. How I am beginning to think it is beyond repair and just run the A/Cs off the generator.
Would someone explain how the system can hold a vacuum and yet quit in less than a hour?
When the tech evacuated the system, it had 3lbs of freon. So there is a large leak somewhere but why a vacuum?
Any direction will be greatly appreciated as I hate to admit to defeat.

Re: Dash Air servicing?

Reply #14 – July 27, 2014, 03:53:45 pm

For dash A/C that will "Freeze your Knees", see Bernd Ramspeck in Nac. Have had to turn it down because we were too cool on our recent trip and that is nearly two years since he fixed it.

Re: Dash Air servicing?

Reply #15 – July 27, 2014, 05:58:23 pm

Is Bernd Ramspeck at FOT? Had considered a trip to Nac, but unless you're otherwise headed that-a-way, it's an expensive detour.

Re: Dash Air servicing?

Reply #16 – July 27, 2014, 06:09:06 pm

Howdy Chad,
Here's Bernd's info.

Bernd Ramspeck
1917 E. Main, Nacogdoches, TX
936-707-1584
Good Luck, Dave A

Re: Dash Air servicing?

Reply #17 – July 27, 2014, 10:01:59 pm

It sounds to me like the compressor seal is leaking. Pulling in a vacuum the seal seals its self. Under pressure it blows it out.

Re: Dash Air servicing?

Reply #18 – July 27, 2014, 10:28:02 pm

Thank you Dave - and everyone else who suggested Bernd; we' ll check it out. Nac IS a longish trip just to get dash-air working again, but more and more apparent it's not a problem with lots of good answers....

Re: Dash Air servicing?

Reply #19 – July 27, 2014, 11:39:47 pm

That sure is a long trip without dash air at this time of year too. I would try to drop in with the coach to see if you can get them to look at it - it's easier for them to say "no" on the phone than it is in person. I would think a truck center might be more helpful. Good chance you might only need some 134A added. Be a shame to drive all the way to NAC for just that.

Re: Dash Air servicing?

Reply #20 – July 28, 2014, 10:31:50 am

John, If system will hold a vacuum and as you say after charge does not cool I would look to a control problem. I am not familiar with the location of the freeze stat on your coach but somewhere there is a control that shuts off the compressor if temp at evaporator is too low. ( likewise there is a control to shut off compressor if pressure is too high ).
I would verify that the compressor is running, if not then bypass the freezstat and see what happens, if it then cools you have a bad freeze stat. Everything has to work together on these systems or it won't work at all.
It is very difficult to determine what is happening with a system if you don't have gauges attached that will show you the pressures in the system.

Gary B

Re: Dash Air servicing?

Reply #21 – July 28, 2014, 11:55:12 am

An over-riding issue for me is the nearly complete absence of knowledge regards where FT hid all the pieces of our dash-air system. I knew we had a bad compressor seal, so had a new Sanden comp installed by Cummins Rocky Mtn. Their techs were not comfortable going beyond that work; said they peaked under the dash hatch as I had suggested, but could not see anything resembling a drier, or expansion valve and were reluctant to explore further for fear of damaging something. I can see what appears to be the plenum, but without disassembly of the dash, can't visualize gaining access to the other component pieces. Pretty frustrating not finding anyone closer than Nac with adequate knowledge of the FT dash-air system. However, that IS preferable to someone causing all sorts of secondary damage by plowing around with no or limited knowledge!!

Re: Dash Air servicing?

Reply #22 – July 28, 2014, 02:56:33 pm

Chad, I have seen on a 97 U295 that the drier , accumulator ( both terms seem to be used ) was located on the left ( street ) side in the last compartment. It is a cylinder about 8 to 10 inches long and 3-4 inches in diameter. It has an inlet and outlet and in some cases it has a glass window on top, Some of them also have a plug where a gauge can be fitted. These don't look too different than the ones you will find on a car, that is if mfg did not hide it behind a fender liner or some such.
Parker Hannifin® W0133-1625688 - Land Rover Range Rover 1987-1989 A/C Receiver
Gary B

Re: Dash Air servicing?

Reply #23 – July 28, 2014, 06:43:42 pm

I am truly (and obviously) ignorant of things A/C.... I have seen what I think you're describing; an 8-inch tall perhaps 2-inch dia filter-like canister, but thought it was related to the Haldex system.

Thank you Gary!

Re: Dash Air servicing?

Reply #24 – July 28, 2014, 10:34:18 pm

On our 99' U270, the the receiver dryer canister was attached to the outside frame rail and was visible through the open hatch behind the street side dualie. I ha to relocate it to the inboard side of the frame member to make room for the extra storage compartment, losing a bit of R134 in the process.
Don

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