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air conditioner U 295-2000 mod

June 15, 2011, 04:42:57 pm

Just been replacing the belts on my Cummins 350 and decided to check the air cond' after setting the belt tension and with the a/c switch on etc the clutch on the pump does not engage. I realise that if the pressure of the system is not correct (that is too low) it will not snap in but was wondering if anyone has had a problem  electrically. There shows on the schematic  a 15 amp fuse (I think) but cannot locate it. Any ideas other than pressure???

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Re: air conditioner U 295-2000 mod

Reply #1 – June 15, 2011, 05:02:02 pm

John,
You can rule out the system pressure as the culprit by bipassing the high pressure and/or low low pressure switch on the compressor.

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Re: air conditioner U 295-2000 mod

Reply #2 – June 15, 2011, 05:20:18 pm

Peter, thanks, just tried that and no clutch working. I disconnected high press' sw and jumped the connections in plug wiring as you said.  Hmmm !
Just now checked pressure and it is almost 0 so that is part of it but as you say jumping it should show if it is something else as well. Still looking for the fuse that shows on diagram but cannot find.

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Re: air conditioner U 295-2000 mod

Reply #3 – June 15, 2011, 05:33:55 pm

John, the low side is the cycling side for the system, the high only cuts out if the pressure is to high,jump the low side and see if it runs, this can indicate ether a bad low side switch or low on freon.

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Reply #4 – June 15, 2011, 06:11:10 pm

Bill I looked for a connection on the low side but could not see any way to jump it as it has a sealed cap and no wiring. The high has one but not on the low!!
here is the schematic showing a fuse.

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Re: air conditioner U 295-2000 mod

Reply #5 – June 15, 2011, 06:56:20 pm

John,from the looks of the photo, someone had a problem with the connector or the switch, I would order a new switch and connector from FT and repair properly, the low side switch may be FT only, the connector is GM,there should not be a sealed connector on the low side.

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Re: air conditioner U 295-2000 mod

Reply #6 – June 15, 2011, 07:16:39 pm

John,
I agree with Bill's observation.  I ordered the Hi & Lo pressure switches from FOT and was sent the wrong ones so I returned them.  I had given FOT Parts the year and model No. of the coach and still sent me the wrong parts.  Also be carefull when removing the Hi pressure switch pigtail.  I had to replace mine as they were fatigued from so many times of removing and reinserting.  They are GM parts as Bill mentioned.  And, I too do not understand why the lo pressure side switch is not wired.  Does your schematic show the lo pressure side wiring?

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Re: air conditioner U 295-2000 mod

Reply #7 – June 15, 2011, 07:23:11 pm

amazing how things progress.
I did notice that there is a wire hanging down below the a/c but have not checked it to see what it is like or fits, I will do that. Now on the schematic it does show that the low side is not connected to anything, only the high side. I have removed the high  connection and it is in good shape so no worries there-yet.
I will now go check that wire and take a picture of the low side schematic
John
 had a look but it is not a connector for the A/C, just a blanked off one from something else. Here is the picture af wiring layout

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Re: air conditioner U 295-2000 mod

Reply #8 – June 15, 2011, 07:45:52 pm

John, remove the wires from the low side and connect them together, this will tell you if the compressor will run, you will need a new switch and connector,without gauges you will not know if it is low on freon.

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Re: air conditioner U 295-2000 mod

Reply #9 – June 15, 2011, 07:54:32 pm

John,
Sometimes the refrigerant leaks at the compressor.  If yours did you can spot the tell-tell signs by looking right above the compressor and see if there is refrigerant oil deposited on the top of the engine compartment insullation (bed cover).  If you have a black light, use it to make a determination.

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Reply #10 – June 16, 2011, 10:18:53 am

Just got done troubleshooting my wife's car A/C.  The problem was that the magnetic clutch was not engaging.  I found the relay was intermittent and the clutch was O.K.  I removed the relay and jumpered the hot side of the relay to the wire to the clutch.  Clutch engaged and A/C worked.  From the schematic portion I see I can tell that the relays are the ever present Bosch relays.  If you can find the relay for the clutch, remove the connector and try to jumper it.

Good luck, at least you have the roof air, unlike my wife's car.  The temperature here in Houston was 102 in the shade at my house!

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Re: air conditioner U 295-2000 mod

Reply #11 – June 16, 2011, 12:16:03 pm

Bill, There are no wires/connection for me to jump for the low side !!!! I have the pressure testing gauges so know the refrigerant is very low. I checked my car to make sure they are ok and that shows good on the pressure, so it is low on the bus.

Peter, I will check for the leak as you say.

John C,  I am at home were it is cool so no worries about heat, but I will have to find the relay for it and right now do not know which ones they are  but will take a third look at plans to see if I can figure it out.
Does anyone know how much 134a is needed in this system as I cannot find it on anything and have not heard back from Foretravel yet??
Thanks.

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Re: air conditioner U 295-2000 mod

Reply #12 – June 16, 2011, 04:51:56 pm

well I think I am getting somewhere as I found the relays and fuse links under the bed on the panel. The centre link is coroded out and came apart. I tested for continuity first and there was not any across the link so that was a good indicater. I have to wait till the morning for a new one to get here before I can put it all back together again and test. This link is hooked up to the ac fan.
I am also going to replace the Relays-just in case and it is always nice to have a spare anyway
Thanks for the help so far
John

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Re: air conditioner U 295-2000 mod

Reply #13 – June 17, 2011, 11:48:21 am

Just a quick note to let the members who ried to help that I have got an answer back from James at FOT and he said that they do not hook up the LOW pressure side just get the signal from HIGH side, so that explains why no wiring. The system takes around 5--5 1/2 lbs of R134a for anyone who has a similar unit.

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