[Tim]

Here is free advice worth every cent you paid for it…………Do it right. In the long run it will be cheaper.

[Archived]

Do not do that. Fix it right

[Archived]

Is it an r12 or newer refrigerant system ? There are various ways of “doing it right”. If it’s an ever small leak in a very expensive place to fix – then it might be worth to just refill the refrigerant every once in awhile.

There are also a lot of places non-Prevost to fix our systems. I think one out in Texas and also aap out of Virginia are both reputable hvac specialists

[Tim]

That vintage OTR is 134A.

Just a guess, but the seal behind the compressor clutch would be the first place I would look. If it has wet oily grease behind the clutch that is likely the issue. 2-3 hours of labor and about $100 for the seal.

[Roscoeapproved]

Jon:

Your right, 134A is the refrigerant. Prevost replaced the rear seal on the compressor back in Dec 2019. Leak test the system at that time and everything was good

Just came form Prevost Winter Garden, they spent two hours just to tell me there was some light oily dirt on the rear side of the condenser (just under the diesel fill). My original reason for going was the AC was not as cold as normal and the receiver tank lower ball was not floating, dryer had some bubbles in it, all indicating a low charge and all right next to the rear side of the condenser.

Not happy; two hours to notice a dirty oily film right next to the receiver tank and dryer that I originally complained about. Then they tell me they need probably 5 additional hours or more to remove the Freon, vacuum the system down, fill with nitrogen to leak check.

Found a charter/transit bus repair shop in Taveras, FL that will remove the Freon, vacuum the system down, fill with nitrogen, leak check and if no leaks found then add a dye and continue searching all for a flat rate fee of 2 Hrs @ $125 per hour. Prevost is into my pockets deeper than that and really didn’t do much more than visually inspect the system.

Prevost Winter Garden has done a lot of good things for me, this one is leaving a bad taste.

Chuck

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Jeff and Lindsay

91 Marathon XL

[DON]

System already had dye in it, technician checked all visible areas with UV light and found no dye/signs of leaks. Removed/Recovered 24 Lbs of 134A from the system, charged the system with nitrogen. Visually check for leaks (found non), let system sit for 2 hrs (no sign of PSI loss). Removed nitrogen, vacuumed system down, refilled until lower ball floated half way up sight glass and dryer sight glass was clear (stop showing bubbles) a total of 27 Lbs of Freon. Added another round of dye, will check for leaks over time.

Not quite sure why it took 27 Lbs to float the lower sight glass ball and have the dryer sight glass run clear when system calls for 24 Lbs.

Couldn’t get high idle to turn on when I started coach, does the OTR air system have anything to do with the high idle working or not working?

[glen]

No, high idle and the OTR ac have nothing to do with ea other. Although, the 24v alternator will be happier producing enough electicity to run all the fans and stuff at high idle than normal idle.

27 Lbs seems to much to me. In a perfect world the ball will float in the middle of the lower sight glass. We don’t live in a perfect world. If ambient conditions are hotter or colder than the perfect world, or if the unloader valves or open or not, or if the condensor door has been open for more than a few seconds. All these things (and more) will change what that little ball does. Its more about what you are seeing for inlet air vs outlet air temps. 30 to 40 degree differential is doable.

The other day I was doing a 45 min ea way trip thru San Antonio on a humid 90 degree day, and my OTR was blowin 42 degree air out the dash and main cabin vents. It cooled the interior of the bus from 87 degrees to 68 degrees in about 20 mins.

What did you do about draining the oil from the compressor sump and installing fresh POE oil?

[DON]

Don:

Thanks for you input, always good stuff. Oil was changed out in Dec 2019 @ Prevost Winter Garden when the compressor seal was changed out. They also had to do something with the clutch. Would have to look up the receipt, old mind doesn’t retain info that long LOL

Condenser door was completely opened in the service position while filling. Didn’t know this would effect the filling process.

Chuck

[Dick]

Where do you guys buy your pressure switches for the Carrier O5G’s, low and high side. Prevost, Welch or elsewhere.

[Bill]

Chuck, check the oil level in the sight glasses about 20 mins after system shutdown with the compressor level.
A good way to see if see if an ac system is under or over charged is by its static pressure at stable ambient conditions, like in the morning, after the sitting all night. Don’t run the engine or ac, hook the gauges up, and read the pressure and compare it to a chart CHART LINK there are many on the web.

Glens, I’ve never needed to purchase any of the pressure switches, but a recent discussion here got me to thinking that it might not be a bad preventative mx move on an old bus like mine. I would go to PrevostCar.

[DON]

Chuck, with the condenser door open, the freon in it is not being cooled efficiently and turned from a gas back into a liquid because the condenser fan(s) aren’t drawing air thru the condenser.

What I do, is run the system for a little while with the door closed, then quickly open the condensor door and take a look see.

[DON]

What the ball is doing is secondary to what the temp of the air is coming out the vents. I’m also watching my gauge set, shooting the temps(IR temp gun) of the heads with the unloader valves, and shooting the temps of the low and high pressure king valves/lines. Blowing cold air(<50*f) is primary.

[Dick]

Don, after reading other posts about pressure overload, Think I need them as mine has dumped freon on 2 separate times in the last couple years. Cheapest thing to try. Pull and install new ones, vacuum system and install R134.

[Bernie]

Don:

Don’t have gauges, was at shop looking over tech’s shoulder.

Got coach home (about 1/2 hr drive) crawled under coach (with condenser door closed & system still running from drive home) and looked up at lower sight glass. Ball was floating at the top of sight glass then liquid and ball fell to bottom 1/4 of sight glass for a few seconds then went back up to top of lower sight glass. Compressor was constantly running (did not cycle off/on).

Unfortunately battery’s are dead in my IR temp gun & couldn’t get temps, but inside was cool after 1/2 run but not an icebox like it normally is (had dash temp set down to 55 – outside temp was 89).

I know over filling will cause less cooling too. based on charge of 27 Lbs and sight glass ball at top of lower sight glass maybe overcharged now. Will get battery’s for IR temp gun and try again.

High idle stopped working all of a sudden, trying to figure that out right now.

Chuck

[Bob]

If an expansion valve goes bad it can do a lot of stuff being discussed. You need gauges on that system because they will tell the story.

I have never heard of system venting to atmosphere unless something was a really high pressure, such as an expansion valve not allowing flow, and that could also contribute to what seems like intermittent refrigerant levels in the receiver.

Gauges. Watching them as a stabilized system cycles is probably going to reveal the whole story.