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BMC (Bluebird Motor Coach Unique Issues) If you have a unique issue with your BMC coach and it can't be answered in one of the other forums here, then this is where you can list it.....List your BMC Parts here too.

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  #31  
Old 05-15-2017
technomage99 technomage99 is offline
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Join Date: Sep 2009
Location: bolton
Posts: 307
Default DASH AIR SYSTEM

GENE: Fine business! You move up in the "Exhalted Order of Skinned Knuckles". Any aches an pains you have endured are just part of your education and you saved a TON of money and prevented your coach from being held hostage by HVAC guys who want to send their kid to college using you as sole financier -- just sayin.

I agree (partially) with John. I tried to organize some more thoughts about
doing a high pressure test below:
1. Before you start the real work:
The service fittings are different sizes and you must
install the "colorful" R12 to
R134a adapter fittings on top of the old R12 fittings with
their O-rings. If the new fittings have Schrader valves,
you have to unscrew and remove the old ones on the R12
fittings underneath.
If you have R134a refrigerant you don't have that
problem. but make sure you have l those
caps (preferably metal) with
O-rings because those little Schrader check valves seem to
be a "weak point". Maybe the little parts are made to loose
tolerances or their little O-rings
don't deal well with R-134a and/or compressor oil -- dunno.
2. I'd make sure the drier is replaced with a temporary hose/pipe
with the correct fittings to mate with the hose fittings.
3. FIND the expansion valve/orfice, remove it and attache and tighten
the fitting it was hiding under. Reason: A high pressure
test might damage or "blow up" the orfice or more likely
blow debris that's in the system into its fine screen.
So, it's gotta go AND make sure you get
a new one for R134a that matches it before throwing it away.
4. I wouldn't worry about needing dry nitrogen for a pressure test as
long as the drier and expansion valve are out.
5. Renting nitrogen bottles is expensive and you need to buy a
regulator for that cylinder.
Plan B is to use a filter and "shop" drier in series (Harbor Freight
or elsewhere again) before
you pressure test. No use introducing shop compressor oil
and water vapor and other contaminants into your system.
You don't need a huge shop drier because the total
capacity of the coach A/C is probably a few quarts.
6. An (almost) whole system pressure test is from the compressor
hoses outward toward everything but the compressor.
The return line would of course have a matching cap or
plug or hose connected to a good shutoff valve.
I'd let the system sit for a day at 200# or
better to see if it holds. If the pressure holds, you are in really
good shape for most of the system.
7. Compressor: Even if the rest of the system is tight, the
compressor could be leaky because it has shaft seals that
can dry out or wear out.
You could do a high pressure test (compressor only) with
appropriate plugs or caps. I'd dump and blow the old oil
out first so that it doesn't interfere with finding leaks. If you put
200# + air into the compressor and because it has a pretty
small volume, even a tiny leak will cause a noticeable pressure drop.
I'd give it a day to sit. If all your fittings in your test rig
to the compressor are "leak tight" and you are losing pressure,
time to buy a new compressor and R134a compatible oil.
8. Before re-assembling I would still blow the HVAC system
cleaner through the system (compressor still disconnected)
just to remove contaminents and blow that out with filtered
and dried air.
9. Install NEW expansion valve/orfice and secure the hose fitting.
10.Install your NEW drier and secure its fittings.
11. Doing a last pressure check minus compressor depends upon
if you feeling lucky?
I would do that test by bringing up the pressure very "gently"
because you don't want to injure the expansion valve with a
sudden blast or wreck a pressure switch or two. I have
NO idea how delicate these things are, but the thought of its
little screen and plastic parts getting
detached and finding there way into the compressor is disturbing.
Filtered dry air is the way go go.
When you are done, bleed the air out slowly.
12. Now you should be ready for "evacuation" of air and moisture
from the entire system with your new or borrowed vacuum pump.
12. If all your gage hoses and fittings are tight you should be
able to pull a vacuum to the limit of the vacuum pump's
capabilities (eventually). If you close the correct gage set valves
except for the low-side gage valve, you should be able to leave it
connected overnight with no vacuum leakage and the gage
should not move from zero.
13. Next, through the gage set fill hose, add the correct number
of pounds or ounces of Freon 134a into the "vacuumed" system.
My SP36 called for 5.5# Freon R12. The equivalent amount of
R134a is 80% or about 4.4#. Your mileage may vary.
You can count freon cans and weigh the last one as it drains to
topoff the last dose of R134a.
I started filling with the engine and AC off, but to finish
I had to start the engine and turn on the A/C to get
the system to "suck" the freon out of the last cans reasonably fast.
It took awhile to get the last
1/2# out ( I had to hold the can upside down up high to do it).
14. You should be feeling cool air by now at the dash.
15. Shut down engine.
16. Close both service valves on the compressor (if you got them).
Remove the gage hoses
and screw the caps on to the service fittings tight with
the proper size O-rings on each.

17. Enjoy cool air!
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1989 SP36
Bolton, Ct.
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  #32  
Old 05-15-2017
Gene Mehr's Avatar
Gene Mehr Gene Mehr is offline
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Location: marblemount wa.
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OK CAL, I have installed many ac systems in classic cars and done many of conversions being a classic car builder. I keep my post small so i don't sound like a over whellming Know it all. If someone has more questions the just can ask. Im very busy and don't have the time to write novels for you. have a good day
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Marcia Mehr
1988 FCSB Silver Edition
82 FC 33 250 left me for another
Sumner Wa.
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  #33  
Old 05-21-2017
Preacher Preacher is offline
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Thanks everyone. I've got enough to work with. WOG people are the best!
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Germantown, Tennessee
1994 BMC37
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  #34  
Old 06-18-2017
markkitch markkitch is offline
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Installed, pressurized and blowing cold!
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1995 WB42
C: 214 477 3757
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  #35  
Old 06-18-2017
technomage99 technomage99 is offline
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Location: bolton
Posts: 307
Default Glad to hear you are blowin cold

Mark:
I'm jealous because your A/C compressor and drier are easily accessible (looking at your picture).

I'm a big fan of doing high pressure testing (at least the highest working pressure of the system) because of experience years ago designing, building and testing high accuracy pressure calibration equipment (which isn't so accurate with leaks). Makes a body paranoid.
In those days we used dry nitrogen since it was easily available piped in.
2nd best is dry air to give the HVAC drier some slack. Since the system has to be pumped out to a reasonable vacuum before sending in the R134a, the drier might give up some moisture it has collected to the vacuum pump. The drier I replaced mine with was larger capacity than the original.

I'd concur with previous posts about old flex hoses becoming a problem. I suspect they will become a problem for me eventually. I don't look forward to debugging any of them because they are "tie wrapped" securely to a bunch of other stuff and hard to get at.
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1989 SP36
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  #36  
Old 06-18-2017
markkitch markkitch is offline
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I went to Harbor Freight, gauges and vacuum pump, $200. Compressor was $315. O' Reilly parts was around $130. So around $700. But, I have some new tools and the experience.
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1995 WB42
C: 214 477 3757
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  #37  
Old 08-07-2017
lfinch lfinch is offline
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Location: Cumming, Georgia
Posts: 51
Default Dash Air

I have a 2003 M380. The dash air blower is not getting power - also there is no power to the driver & passenger windshield shades.
There must be a bad relay - can anyone help me locate the guilty relay?

Note: Must be a defective relay because the blower would come on when I drove over a bump in the road and actually stay on - but now doesn't come at all.
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  #38  
Old 08-07-2017
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Gatorgrl Gatorgrl is offline
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Quote:
Originally Posted by Ernest Ekberg View Post
had 4 birds- none of those worked, just run genny
Are you suggesting running the genie the entire time you are on the road as well as at the campsite?
We are Floridians and don't drive anywhere without the a/c blasting.
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Tony (The Grumpy Mechanic)

Lee County, Florida

1983 FC35 3208T "Gen X Express"
1991 Toyota 4Runner TOAD or
1980 Camaro TOAD

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  #39  
Old 08-07-2017
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We run the generator while driving. Don't shut it off until ready to plug in. If no power available, run it several hours a day. On the last long trip, the Onan ran for 3 days straight.
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  #40  
Old 08-07-2017
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Well I guess we better get that ole Perkins up and running then...or replace it.
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Tony (The Grumpy Mechanic)

Lee County, Florida

1983 FC35 3208T "Gen X Express"
1991 Toyota 4Runner TOAD or
1980 Camaro TOAD

danahcks@aol.com
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