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Elite Veteran
 
Location: Victoria, BC. Canada | Howdy,
A couple of the last significant things I need to deal with on #846 are, 1) Dash & rear-cabin A/C are not blowing cold; 2) Coach wanders a bit still and requires constant attention/corrections at HWY speeds; 3) Genny won't run but I've got a line on a good (130/lb) Yamaha 6500 to solve this issue.
Today I need to ask for help with diagnosing engine A/C issues.
This is what I've determined so far:
- a PO has wired a toggle switch to the dash (next to the rotary heater fan knob) that turns on the lower A/C fans under the front of the coach. They both appear to run.
- I also discovered that the sliding 'Heater' on-off knob that controls a hot-water valve below the domestic panel, was sticking. I've since freed it up and it opens and closes now.
I'm assuming one needs to stop the flow of 'hot' engine coolant in order to use the A/C.
- the other sliding 'Selector' control knob ('Def'-'A/C'-'Heat') appears to move the cable from one selection to the other, but there seems little confirmation 'by-feel' that you're actually set in the correct position. I know with 'Defrost' you should feel the heat airflow coming up onto the windshields and with it on the 'Heat' setting you should feel it more on your feet. I'll have to get down and see what happens to that cable control - whatever it's hooked up to - actually does.
- the rear A/C unit appears to blow okay but doesn't get cold at all. The front one blows ever so slightly cool that I can't say with any certainty that it's doing anything.
I noticed after checking the A/C lines from the compressor on the engine that one of them has a little round plastic white cap covering what appears to be an inspection window for something. What should I guy be looking for in there? Is it a freon level indicator window? Perhaps if the system needs re-charging, it's out of my league regardless.
The FMC Parts Manual has pretty good content on the engine A/C system but, unfortunately, there is not much in the 'Service' manual anywhere on diagnosis, troubleshooting/repair or specifications. Even the smaller 'Owners Manual' don't elaborate much on using the coaches A/C system.
If any of you can offer up a primer on what steps to take from here to sort this out, I'd be much obliged. I'd much sooner get advice from my fellow FMC'ers before I take it to a service outfit that don't know about these coaches. It will also be good reference for future owners with the same issues.
Thanks in advance.
Terry
#846 |
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Veteran
Location: Olympia, Washington | Ready Terry?
The little window is referred to as a 'sight glass' it is a window to watch the freon. Actually you are seeing bubbles of freon gas boiling out of Freon liquid. First and foremost the compressor must spin! Most systems prevent the compressor from operating while low on Freon which is a good thing, keeps from burning it up. The refrigerant oil in the system requires Freon to circulate it, no Freon no oil! Back in the olden days before 'Ozone Layers' Freon or R-12 systems regularly lost a pound a year and we considered that normal. In fact a 24 foot length of refrigerant hose would lose a pound a year at the molecular level right through the hose. Systems in those days averaged 3 to 5 or more pounds, Freon was cheap and no one cared about killing penguins. It would be quite a miracle to have any Freon left in the system but it is still possible. Check for pressure at the service ports (shraeder valves just like tires) a warm engine will pressurize plain air to 30 - 40 psi. in the system don't be fooled by air Freon will 'ice' up your fingers so be careful you don't won't frostbite! So assuming empty system 1) check compressor, does it turn? Not the belt the 'face' of the clutch must turn, the belt is on bearings and spins any time the engine does. 2) Leak check system, usually accomplished by pulling a vacuum and see how long it holds. If vacuum holds then shoot Freon in and pressure test. If it passes the pressure test install the correct amount of Freon and move on to the performance test. 3) Performance Test: Engine Off: Sightglass = Clear, High Side pressure = Low Side pressure, Air temperature in = temperature out. Engine running & Compressor Spinning: High Side pressure = 150 - 350 psi, Low Side Pressure = 30 - more than 0 psi, Sight Glass = clear or bubbles, Air Temperature in warm, Air Temperature out cool. Sight Glass: Not operating = Clear, Operating with the correct amount of Freon = Clear. WHAT? That's right working and not working the sight glass looks the same. System Operating with less Freon than required = bubbles. As you added Freon to an under charged but operating system you watched for bubbles in the sight glass, when the bubbles disappeared it was full. R134-A systems do not include a sight glass as the system charge is much smaller and must be accurately weighed to operate correctly. Any questions? This is a subject I spent 30 years getting good at and now I don't do any more. :-( |
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Elite Veteran
Location: Victoria, BC. Canada | By George - by Gosh! What a great response and thanks so much. In the middle of burning up some chicken legs on my barbie. Give me a bit to digest what you wrote and I'll likely have a question or two.
Did you guys get that thunder-storm and downpour today? We got hit pretty good; almost washed the FMC! Good for the forest fires I suppose.
Again, thanks!
Terry |
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Veteran
Location: Olympia, Washington | No thunder here, barely enough rain to wet the roadway. Besides this isn't dry I just spent a week at my kid's house, it hit 102 f in Richland way too hot for me. The true sign of dry has to be ...... Sagebrush! I don't like naked hills, I like my hills wrapped in evergreens. I used to have a pocket AC pressure gauge (think tire pressure gauge only bigger) that answered 'a little or a lot' to how much? Ask away I would be happy to help. |
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Dash A/C Troubleshooting?
