NO A/C Help !

[RCMerrill]

I have taken my truck to get the A/C looked for $85.00 at they said the compressor is shot oil is leaking all over , but when i got home i looked under the truck & it has no signs of any kind of leaks . i was going to put a can of freeon in but i can only find one port by the heater. i was reading someones post about there a/c problems & they said they had 60 psi on low side & 0 on high i don`t see another fill or test port. summer is here & its getting hott.. can someone help walk me through what to do. Ray. my truck is a 2006 Ram 2500, diesel.

 

[Tuesdak]

2nd opinion at another shop. Possible they cleaned the oil off the compressor to help find leaks.

These systems are charged by weight and take special tools to find leaks. The path of least resistance to cold air is a good AC shop. Where you at as members can suggest places or maybe help in person.

 

[Bob4x4]

2nd opinion at another shop. Possible they cleaned the oil off the compressor to help find leaks.

These systems are charged by weight and take special tools to find leaks. The path of least resistance to cold air is a good AC shop. Where you at as members can suggest places or maybe help in person.

Well said,the 06 is famous for shorted coil-that will shut down the output from the tipm and trip a code

 

[Motorhead]

The LOW side port on the receiver drier by the fire wall is where refrigerant is to be added. Never to the high side. The high side port on my 2007 is right at the radiator support by the air cleaner box. Does the AC compressor clutch engage when the AC is turned on? High and low side pressures can vary depending on ambient outside temperature.

Here is a STATIC pressure chart. Meaning compressor not running and measuring the system pressures according to the ambient temps. So if the system is reading 85 psi and the outside temperature is 78.98 degrees, the system is perfectly charged.: http://www.pacificseabreeze.com/tech-library/heat-and-insulation/R134a-PT-Chart.htm
Here is low and high pressures with the system running according to ambient temps: http://acprocold.com/faq/r-134a-system-pressure-chart/

 

[Tuesdak]

The LOW side port on the receiver drier by the fire wall is where refrigerant is to be added. Never to the high side. The high side port on my 2007 is right at the radiator support by the air cleaner box. Does the AC compressor clutch engage when the AC is turned on? High and low side pressures can vary depending on ambient outside temperature.

Here is a STATIC pressure chart. Meaning compressor not running and measuring the system pressures according to the ambient temps. So if the system is reading 85 psi and the outside temperature is 78.98 degrees, the system is perfectly charged.: http://www.pacificseabreeze.com/tech-library/heat-and-insulation/R134a-PT-Chart.htm
Here is low and high pressures with the system running according to ambient temps: http://acprocold.com/faq/r-134a-system-pressure-chart/

All that pressure means is you have a little liquid R134a in the system. Could be overcharged, perfectly charged, or nearly empty. The static pressure is going to be the same with 1/4 lb of R134a as it is with 3 lb. Same on that 30 lb cylinder full or nearly empty. This and the way orface tube systems act is why you have to charge systems by weight.

There is no shortcut to recover, vacuum for 15 min, and recharge the system. Then you leak check the system with a sniffer to try and prevent a return unhappy customer in the middle of the summer.

 

[Motorhead]

I disagree with you as I have checked several AC systems at static pressures and when they were at the noted pressures, they worked fine. If you read the whole post, I also listed RUNNING pressures to ambient temperatures.

 

[Tuesdak]

I disagree with you as I have checked several AC systems at static pressures and when they were at the noted pressures, they worked fine. If you read the whole post, I also listed RUNNING pressures to ambient temperatures.

Take into consideration your audience that really doesn't have much AC knowledge or how to diagnose their AC. You are doing a disservice to people by telling them they can do what even experienced professionals can't do! The Low or High is meaningless esp. if they don't have or obtain a quality temp probe to make sense of it. Also take into consideration the fixed orface tube vs. TXV and other designs out there that have different ways to figure the system charge. The OEM service manual tells you to service the AC in a specific way and that is if there is ANY doubt as to the state of charge - recover it and recharge by weight. With all orface tube systems there is no way to tell the system charge accurately enough by running pressures. (However, an antique expansion valve system running R12 you get a sight glass for bubbles sometimes. And you have to make sure it isn't installed backwards.) What's the first step of troubleshooting an AC system where the pressures are weird: start with a known charge so the running pressure readings mean something. After all you are working on the AC for a reason.

Pressures, static, only tell you that you have some liquid in the system period. Tell me again how static pressures tell you how much of the critical charge is in the system again? Sure when the system is INOP as it's completely out of liquid will the static pressures drop. Running pressures and temperatures troubleshoot the AC and cooling system, but, do not accurately tell you what the charge level is. (Drop a VOV orface tube in like the link I gave and your running pressures will be completely different than you are used to.) Going by pressure alone you can send a vehicle down the road that will come back not working as the "load" changes and then the wrong system charge is discovered. A low charge is expected as well as overcharge from the $50.00 do it your self charge kits the owner attempted before going to a pro.

Last consideration to halfassing the system charge procedure: if the charge is below the critical charge where only gas leaves the evaporator how does the oil get out of the evaporator? Simple, it doesn't. This leaves you with a oil starved locked up compressor, debris in the system, and all the oil stuck in the evaporator. With the smaller charges used in the newer eco-friendly vehicles the margin of error is so small that new accurate recovery/charge systems are required and even the recovery/charge system's hose length to the vehicle is a major factor. It's one reason the new stuff is going TXV over the obsolete and poor performing orface tube designs of the past.

 

[tgee43]

I have to agree with Motorhead. I have done lots of A/C work, and can say I can tell by high and low side pressures whether a system is low or
overcharged. I can also get a system working good with out having measured the amount of freon I added by watching pressures and by feeling the lines temps. This leads me to a question. My 07 5.9 has crappy A/C, not enough cooling. Ambient temp 80 degrees, engine idling, low side psi @ 40, high psi will creep to 400 ish, fan comes on, high pressure drops to around 250, low side line ice cold. Blend door linkage and motor appear to work correctly. I think door not sealing properly, dumping too much heat load on evaporator. Any one else have this problem? Truck kinda new to me.

 

[Motorhead]

You might try recovering (venting) a little 134 off from the low side to drop the overall charge. I have found a real fine line that at just a bit on the undercharged line, you get the good cold air. 400 on the high side at only 80 outside air sounds high to me. Your system might be over-charged. Some guys have installed an under hood heater core shut off. If your truck has the manual knobs to adjust heat and cold then the heater core is hot all the time and they use the blend doors to regulate. By closing off the heater core, guys here have said that they improved their A/C by quite a bit.

 

[PWong]

07 5.9 has crappy A/C, not enough cooling. Ambient temp 80 degrees, engine idling, low side psi @ 40, high psi will creep to 400 ish, fan comes on, high pressure drops to around 250, low side line ice cold.

According to the 05 FSM A/C Performance Temp and Pressure Chart: ambient = 80F, low side = 25-35, high side = 200-300, temp at Center Panel Outlet = 45F, idling at 1000rpm.
According to the A/C Pressure Diagnosis Table:
Condition: Low side is normal or slightly high, and high side is too high.
Possible Causes: Condenser air flow restricted, Inoperative cooling fan, Refrigerant system overcharged, Air in the refrigerant system, Engine overheating.

The cooling fan is supposed to kick in when refrigerant pressure rises above 240 psi.

Your fan came on at 400 psi, too late.
And the high side pressure dropped back to normal after fan came on.
If the low side pressure also drop back to normal then I would say the refrigerant level was OK and the cooling fan wasn't working properly.

I would try to replace the pressure transducer.

 

[Tuesdak]

I suggest open you mind to how the AC system actually works rather than how you think it works. I do apologize as this information is not widely or easily available and, in fact, discouraged by the EZ $50.00 charge kits sold in auto parts stores. They also sell compressors and encourage you to try again...

One of the fellows who spearheaded the development of the FOT GM/Chrysler Corporation explains the 'some liquid' leaves the evaporator. Not talking about a solid liquid stream here. Some liquid leaving being the point of do the job properly as too little or to much in the system messes with it performance. Again due to this narrow charge range is why I suggest just tossing a can into the system that winds up cooling can be low or overcharged and no way to tell.

“Flooded” means that the evaporator core is designed to operate under conditions where some liquid leaves the evaporator and flows into the suction accumulator. The amount of flooding, or “overfeeding,” is usually five to ten percent of total refrigerant flow. This generally is equal to the “liquid bleed” from the accumulator
http://www.imcool.com/articles/aircondition/VOV3.htm

Check it out and if you find an article on oil return or oil flow in the FOT systems I am sure it would be interesting.

 

[tgee43]

According to the 05 FSM A/C Performance Temp and Pressure Chart: ambient = 80F, low side = 25-35, high side = 200-300, temp at Center Panel Outlet = 45F, idling at 1000rpm.
According to the A/C Pressure Diagnosis Table:
Condition: Low side is normal or slightly high, and high side is too high.
Possible Causes: Condenser air flow restricted, Inoperative cooling fan, Refrigerant system overcharged, Air in the refrigerant system, Engine overheating.

The cooling fan is supposed to kick in when refrigerant pressure rises above 240 psi.

Your fan came on at 400 psi, too late.
And the high side pressure dropped back to normal after fan came on.
If the low side pressure also drop back to normal then I would say the refrigerant level was OK and the cooling fan wasn't working properly.

I would try to replace the pressure transducer.

Good info, thanks. I kind of suspect air in system. Not sure what was done by previous owner. I will recover system, give it a long vacuum to remove any moisture, and fill with proper amount. Will also replace transducer. Gotta ask boss if alright to use shops A/C machine! Funny thing, I have a 98 1/2 with 230,000 miles, never touched A/C, will freeze you out.

 

[Tuesdak]

I have to agree with Motorhead. I have done lots of A/C work, and can say I can tell by high and low side pressures whether a system is low or
overcharged. I can also get a system working good with out having measured the amount of freon I added by watching pressures and by feeling the lines temps. This leads me to a question. My 07 5.9 has crappy A/C, not enough cooling. Ambient temp 80 degrees, engine idling, low side psi @ 40, high psi will creep to 400 ish, fan comes on, high pressure drops to around 250, low side line ice cold. Blend door linkage and motor appear to work correctly. I think door not sealing properly, dumping too much heat load on evaporator. Any one else have this problem? Truck kinda new to me.

Looks like you are not alone with the high side spike. There appears to be some sort of condition where the engine is cold, not enough fan is commanded and the ECM doesn't shut off the compressor with extreme high side pressure. Instead of shutting off the compressor the system pops the high side safety relief valve resulting in a low system charge. (And the warm passenger side the thread I link starts out with.) Looks like they had a D/C engineers ear. They tried near everything from larger FOT, different condenser, compressor, electric fan strapped to the condenser...

You wouldn't expect a working system to randomly blow off the high side safety valve as a source of a leak.

Related I have seen other Electro Viscous fan equipped vehicle refuse to command the fan for 2 full minutes after engine startup allowing ECT to run away and AC to kick out from high high side pressure. Wonder if it's related to the EV suppliers suggested programming? But, that wouldn't explain why the compressor simply isn't shut off with extreme high side pressures.

http://www.dieseltruckresource.com/...years-101/03-ac-not-working-pass-side-106452/

Long term results of electric fan on condenser:

http://www.dieseltruckresource.com/forums/3rd-generation-ram-non-drivetrain-all-years-101/04-5-c-passenger-vents-not-cold-drivers-side-245620/

 

[RCMerrill]

I have taken my truck to get the A/C looked for $85.00 at they said the compressor is shot oil is leaking all over , but when i got home i looked under the truck & it has no signs of any kind of leaks . i was going to put a can of freeon in but i can only find one port by the heater. i was reading someones post about there a/c problems & they said they had 60 psi on low side & 0 on high i don`t see another fill or test port. summer is here & its getting hott.. can someone help walk me through what to do. Ray. my truck is a 2006 Ram 2500, diesel.

Well i got the truck back I had un pluged the clutch on my compressor & put 12+ on one pin & ground on the other & the clutch did not kick in with engine does anyone know what resistance should i read in Ohms across the clutch.

 

[PWong]

Well i got the truck back I had un pluged the clutch on my compressor & put 12+ on one pin & ground on the other & the clutch did not kick in with engine does anyone know what resistance should i read in Ohms across the clutch.

3 - 6 ohms.
You need a new clutch.

 

[sag2]

Looks like you are not alone with the high side spike. There appears to be some sort of condition where the engine is cold, not enough fan is commanded and the ECM doesn't shut off the compressor with extreme high side pressure. Instead of shutting off the compressor the system pops the high side safety relief valve resulting in a low system charge. (And the warm passenger side the thread I link starts out with.) Looks like they had a D/C engineers ear. They tried near everything from larger FOT, different condenser, compressor, electric fan strapped to the condenser...

You wouldn't expect a working system to randomly blow off the high side safety valve as a source of a leak.

Related I have seen other Electro Viscous fan equipped vehicle refuse to command the fan for 2 full minutes after engine startup allowing ECT to run away and AC to kick out from high high side pressure. Wonder if it's related to the EV suppliers suggested programming? But, that wouldn't explain why the compressor simply isn't shut off with extreme high side pressures.

http://www.dieseltruckresource.com/...years-101/03-ac-not-working-pass-side-106452/

Long term results of electric fan on condenser:

http://www.dieseltruckresource.com/forums/3rd-generation-ram-non-drivetrain-all-years-101/04-5-c-passenger-vents-not-cold-drivers-side-245620/

If I recall there was a flash for the early trucks to turn on the fan for better A/C performance when the engine was cold.

 

[Bob4x4]

If I recall there was a flash for the early trucks to turn on the fan for better A/C performance when the engine was cold.

Yes there was and it did help fix the fan clutch coming on a cold engine with ac on

 

[Killer223]

done you just jump the terminals at the pressure sensor.? i've never worked with a dodge, but i know on a GM you could jump the sensor and the clutch would engage. that's how we'd charge them after vacuuming them down. (with engine intake vacuum.) worked like a charm.
my Yota still uses R12, and it's bloody COLD at 28* out the vents where my 04 dodge will only get to 40.

It's easy enough to vacuum them down. then charge it back up. that's the route i'd go.

 

[Rmax]

first would like to say new to the forum ,thanks for the add
first time diesel owner 2008 2500 dodge ram 6.7 cummins

just replaced my orfice tube today an charged system was wandering about the pressures thank for the chart

 

[tgee43]

Well, I discharged system, vacuumed it for over an hour, than added about 2 pounds of freon. system works ok for now. Did not replace the transducer, because I saw high side pressures normal, fan doing it's thing. Wonder if it was air in there.