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Author Topic: MCI bus AC  (Read 5230 times)
paul102a3
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« on: July 08, 2009, 04:53:31 PM »

Our bus AC has been working just fine until today. Since the beginning of April, the bus AC has been on quite a bit with no issues. We last used the bus 3 weeks ago to cross from the west coast of Florida to the east coast and back with no AC problems (I did notice the bus was not as cold as it was earlier in the year but I chalked that up to the 20 degree increase in ambient temp).

I did a quick trip in the bus today and had little to no cooling from the AC system.

A quick check of the compressor shows a lot of bubbles in the sight glass so I assume I am low on refrigerant. While I can take the bus in for service, I am wondering if there is a common spot for these systems to leak freon so I can maybe resolve the problem myself. 

Any advice would be appreciated.

Paul
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2001 Prevost XL II
John316
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MCI 1995 DL3, DD S60, Allison B500.




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« Reply #1 on: July 08, 2009, 05:31:53 PM »

Paul,

I feel for you. My question is, "how did it lose the freon?" Probably through a leak, but don't worry, there are only 141 fittings on there, 58 of which are inaccessible Grin Tongue Grin. One of those probably worked themselves loose...Simple fix, once you find the problem Shocked Grin Shocked.

Sorry about your trouble, I really don't have any advice. That is the reason that we took ours out and sold it. Too much $$$ put into that system.

God bless,

John
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MCI 1995 DL3. DD S60 with a Allison B500.
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« Reply #2 on: July 08, 2009, 05:47:17 PM »

Hey John, where did you sell it? Roll Eyes
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« Reply #3 on: July 08, 2009, 06:43:06 PM »

M&C, Actually I sold it to a really neat guy, named Paul, down in Florida (on the west coast I believe). Grin Grin Grin

I am kidding. We actually sold it to a bus lines. They gave a good penny, because they still run a lot of our D model coaches.

God bless,

John
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MCI 1995 DL3. DD S60 with a Allison B500.
Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #4 on: July 08, 2009, 06:58:43 PM »

Hi Paul,

You can do a simple leak test yourself. Since you see bubbles in the sight glass, you do have quite a bit of refrigerant left in the system.

So, just mix up some dish detergent and water in a squirt bottle and start spraying everything you can find in the system. Like fittings,

hoses, condencer coil, compressor shaft between the clutch and the housing. The most common places for leaks are in the condencer

compartment. Rusty acuumulator tank, or leaking fittings are most common. Also see if the last person that charged the system reinstalled

the caps on the charge ports..

Good luck
Nick-
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paul102a3
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« Reply #5 on: July 08, 2009, 07:13:53 PM »

Nick,

Thanks for the advice. I'll start on it tomorrow and see what I can find.

Paul
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jmblake
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« Reply #6 on: July 08, 2009, 07:23:02 PM »

We just got ours going again tonight, our leak was in the preasure switch back at the compressor. The previous owner or someone didn't use the right switch and that made it that much more confusing. Just in time as we are leaving for VA beach Friday. I would also like to thank Nick for all his help. Jason
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Nick Badame Refrig/ACC
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« Reply #7 on: July 09, 2009, 06:19:20 AM »

We just got ours going again tonight, our leak was in the preasure switch back at the compressor. The previous owner or someone didn't use the right switch and that made it that much more confusing. Just in time as we are leaving for VA beach Friday. I would also like to thank Nick for all his help. Jason

Jason,

Thanks..

I hope your going to Holiday Travel Park in VA Beach? I think it's the best there...

Have fun
Nick-
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« Reply #8 on: July 09, 2009, 07:24:16 AM »

 Grin LOL, Thanks John
« Last Edit: July 10, 2009, 09:01:04 AM by Singing Land Cruiser » Logged

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paul102a3
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« Reply #9 on: July 10, 2009, 05:52:53 AM »

Well, I feel a little foolish (kind of normal for me) as I was looking at the wrong sight glass. Upon further inspection it appears that I do have plenty of freon in the system however I still have no cooling.

When I hit the AC switch on the dash, the compressor clutch engages, the condenser fan turns on, the evaporator blower turns on but no cold air.

I do have someone coming on Monday to put some gauges on and take a quick look. He works primarily on marine AC and refrigeration systems but does have some knowledge of bus systems as he owned a converted Eagle for a number of years.

Any quick things I can look for this weekend to get the system working and maybe save a service call?

Paul
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Nick Badame Refrig/ACC
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« Reply #10 on: July 10, 2009, 09:04:59 AM »

Hi Paul,

The unloaders on the compressor could be open. They ate externally mounted on the compressor.

Just a thought....
Nick-
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paul102a3
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« Reply #11 on: July 10, 2009, 09:22:49 AM »

I have a little more info now that I have been playing around.

The main AC relay located under the drivers side widow energizes as does the liquid line solenoid when I turn on the dash AC switch. The one thing I just noticed is that the AC "on" light located next to the temperature adjustment controls does not come on as it did before.

If the unloaders were open, would that cause the system to think it was off?

Lastly, the smaller of the two lines to/from the compresser gets real hot real fast while the bigger line stays at ambient temp. Does that mean anything?

Is it possible the expansion valve is stuck/clogged not allwing freon to circulate?

Thanks.

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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #12 on: July 10, 2009, 05:27:32 PM »

Hi Paul,

The best way to find the answers to your questions is to put a set of guages on the system to accuratly see if the refrigerant is flowing.

If there is a restriction, you will see it on the guages.

Nick-
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paul102a3
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« Reply #13 on: July 16, 2009, 09:42:54 AM »

Nick,

I had a friend of mine stop by with his gauges and here is what we found. Engine running at high idle, high side 120 and the low side 23. The high side would climb about 15 psi with the condenser door open.

We added a small amount of 134 and the head pressure climbed a few pounds but not significant.

My friend didnít want to go any further as the bus system is too different than the Crusairs he normally works on.

One last thing and I donít know how significant this may be but the hot water system for the bus is shut off. I was reading an article that stated the hot water circuit should be on in order for the system to work correctly.

Any thoughts or suggestions?

Thanks,

Paul
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justin25taylor
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« Reply #14 on: July 16, 2009, 01:38:30 PM »

Nick will post again I'm sure, but that high side number is too low. I wouldn't be afraid to add some more refrigerant. Look at the 134a temp scale on your gauges. You want to add 30 degrees to the ambient temperature and try to get the high side close to that. There are several variables but that will get you a lot closer than you are now. Low side should be 30-40 range (again some variables exist)
Good Luck,
Justin
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