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Topic: Ac compressor power (Read 308 times) previous topic - next topic

Ac compressor power

Hey all, hope everyone is staying cool.
So my ac has not worked since  purchasing it several years ago. So far I found that my compressor isn't kicking on when I turn it on at the dash. My dash switch is working and I have power at the switch but when I unplug the single line, I believe it to be a 12 V wire going to the compressor  I can't get any voltage. I'm wondering if anyone knows if that circuit goes through a breaker or a few somewhere? Thanks

1999 U320. 
James and Suzi
1999 U320  36, Cummins M11
Build 5544  Motorcade #17268
Ronan, Montana
2020 Jeep gladiator

Re: Ac compressor power

Reply #1 –
James,

Do you have the B-2179 12V Wiring Diagram for your coach?  If not, the one from the Forum Library (linked below) should be close.  Looking on the diagram, in the upper right corner, just to the left of the battery isolator, you will see the Air Conditioner relay and associated 15A auto reset circuit breaker.  You might check these two items to see if either of them has failed.

https://www.foreforums.com/index.php?media/file/b-2179-e24-12v-wiring-diagrams.4747/

You can see the same A/C relay on the B-2126 Diagram below.  Relay is in center of the diagram, above and to the left of BOOST solenoid.

https://www.foreforums.com/index.php?media/file/b-2126-automotive-wiring-u270-295-320.3297/

Also see the A-6122 diagram linked below (scroll down to see all 3 sheets).  May help with tracking the power flow to your A/C compressor.

https://www.foreforums.com/index.php?media/file/a-6122-ac-comp-hi-lo-press-switches.3283/


1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Ac compressor power

Reply #2 –
When you turn the AC on while the key is on or engine running, does the condenser fan come on? 
Keith
2003 U320 38' #6197

Re: Ac compressor power

Reply #3 –
James, more than likely it's low on Freon from no use and other factors. Find a good auto a/c tech to connect some gauges to the system, he will be able to tell you what is needed. Otherwise like a needle in a haystack. Jim. 
Jim and Dona
2002 U295 36'
Lily, blue healer. Our fury person
Manx mid travel Ecotec turbo
2022 Bronco badlands Sasquatch
Trail 90 and 110cc

Re: Ac compressor power

Reply #4 –
I do understand that a ac guy would be the best route. I'm trying to save possibly some money by putting in some freon, but it won't take it I believe because the compressor isn't engaging. If it needs more work than adding freon it will have to wait for awhile due to funds. Hey Keith, I don't know if the condenser fan is running or not and besides, where is it located in the dash somewhere? I'm adding a couple pictures and I'm curious if anyone knows if the black wire in my hand is what turns on the clutch and the compressor.
James and Suzi
1999 U320  36, Cummins M11
Build 5544  Motorcade #17268
Ronan, Montana
2020 Jeep gladiator

Re: Ac compressor power

Reply #5 –
Quote from: Gold Nugget finder –
Hey Keith, I don't know if the condenser fan is running or not and besides, where is it located in the dash somewhere? I'm adding a couple pictures and I'm curious if anyone knows if the black wire in my hand is what turns on the clutch and the compressor.

Turn the key on (or with engine running) turn on A/C.  Condenser fan should run.  It's mounted to the back side of the condenser, which is at the rear, street side of the coach.  Looks like another radiator/cooler and is up against the street side louvered rear most bay door on my coach.


Keith
2003 U320 38' #6197

Re: Ac compressor power

Reply #6 –
So, I'll be the bad guy and present some information for servicing AC units.
First, while auto parts stores sell refrigerant (R-134a) and additives and kits, those small quantities are sold to skirt the laws regarding distribution and use. You need to have certain certifications to purchase refrigerants and service AC systems. You also need specialized equipment.
Of the equipment required is the ability to recover it. You can't intentionally vent refrigerant and if a leak is discovered while filling or testing you need to be able to recover it. You also can't fill a system that is known or suspected of having a leak.

Now for the next part, servicing it. If the refrigerant has leaked out, then moisture and air has entered the system. In, fact even in working systems moisture sometimes gets in. That is why there is the receiver/filter/dryer. This has a desiccant to absorb moisture. In addition to refrigerant there is also lubricating oil. These compressors actually have pistons and valves and need oil just like engines. The quantity of oil is critical as it is also a contaminant to the refrigeration process. Too much and it lowers performance of the system and can also do damage.
With the system devoid of refrigerant and subject to moisture contamination there can be rust and corrosion inside. Steel parts and fittings will rust, copper and brass parts will have that green corrosion, and aluminum parts will have that white crusty stuff. 
If you simply add refrigerant this stuff can come loose and clog things up. Also, moisture in the system can form ice crystals and if critical parts such as the expansion valve or orifice tube get clogged the high pressure cut out (if one is there), may not respond in time and you can then blowup hoses and instantly destroy the compressor.  Now you have metal parts throughout the system.

The approach for this sort of goes as follows:
1) Charge system with nitrogen and test that it can hold pressure for 24 hours.
2) Locate all electrical components and wiring and test each. Thermostat and pressure switch controls.
3) If pressure test is good, open system at all key components. Remove receiver/dryer, replace later. Flush using suitable fluids and methods. Flush all solvents out. Avoid using compressed air, use nitrogen. Be sure condenser and evaporator are clean and not damaged on outside.
3) Remove compressor and drain oil. Find required oil amount and fill compressor with the amount it holds and inject the rest the system needs when charging. If replacing compressor, it will likely be pre charged. Match type for rest of system. 
4) Reassemble everything with new O-rings and gaskets. Install new Receiver/Dryer. Nitrogen pressure test again.
5) Evacuate system. Pull vacuum down as low as possible. Since system was opened and contaminated consider a 24 hour "pull down".
6) Proper equipment should be able to fill system by "weight". Fill and include required amount of oil.
7) Turn system on with gauges connected. Refrigerant amount will likely need some adjustment due to all those hoses. Observe sight glass for refrigerant motion and oil being carried. Make sure condenser fan is working, may be multi speed.

Hopefully you now have working AC.

Dennis Haynes
Bohemia NY
2008 Nimbus 342 SE Carlyle
Build #6475
Motorcade #19148

Re: Ac compressor power

Reply #7 –
Quote from: Gold Nugget finder –
I do understand that a ac guy would be the best route. I'm trying to save possibly some money by putting in some freon, but it won't take it I believe because the compressor isn't engaging. If it needs more work than adding freon it will have to wait for awhile due to funds. Hey Keith, I don't know if the condenser fan is running or not and besides, where is it located in the dash somewhere? I'm adding a couple pictures and I'm curious if anyone knows if the black wire in my hand is what turns on the clutch and the compressor.
James I sent you a pm, Jim.
Jim and Dona
2002 U295 36'
Lily, blue healer. Our fury person
Manx mid travel Ecotec turbo
2022 Bronco badlands Sasquatch
Trail 90 and 110cc

Re: Ac compressor power

Reply #8 –
Yes that wire turns the clutch on. If the Freon is low the clutch won't engage. So if it is low you
should be able to add Freon and having the engine running while filling it the clutch will engage
when the pressure is high enough. The condenser fan comes on when the AC and key is on and
the relay for that is with the rest of the wiring when I lift the bed on my coach.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Ac compressor power

Reply #9 –
With a coach that old and no history you can expect to put a new compressor, dryer, expansion valve, new end fittings on hoses to compressor, 4.5 pounds of refrigerant, flush the lines with 90% ispropol alcohol and 5 hours of labor by someone who knows what they are doing.  You will not get off cheap by trying yourself.  Just had mine done and the cold air is magnificent.
Jerre and Kathy Griffin
2003 U320 4220 Special
Build # 6207
2022 RAM Laramie 4X4 EcoDiesel
2002 Country Coach Magna 37 Tag- Forever Coach-Died in fire 7/23
1997 Country Coach 32 Intrigue-No slides-Wonderful