freightliner columbia A/C losing freon out relief valve

[mweiman]

I have a truck at work that losing freon, it appears to be out of the relief valve on the back of the compressor. It has done this at least 6 times, maybe more. Here are the details:

Truck is a 2006 freightliner columbia with a 60 series detroit, sleeper.



Original problem the compressor locked up and clutch was burned up, compressor was replaced and receiver dreir at the time, along with cab filters. System was basically full of freon when the first compressor was removed. After that it has been losing freon out of the relief valve. Tried recharging and locked engine fan in to run all the time. Then tried another compressor and problem continued. That compressor ending up locking up and burning the clutch up after 2 or 3 times being charged. Reinstalled the other compressor.



Tried overcharging the system to test the high pressure switches in the receiver drier to see if they were shutting compressor off at high pressure, they were working but replaced them anyway along with the relay for the compressor. Leaked out again, another guy charged it in the shop and the condensor started spraying out the front where the grille screen had rubbed it a little. Replaced the condensor and thought it may have been the leak and the fan was spraying the freon around. Lost freon again, yesterday I replaced both expansion valves(cab and sleeper) and hose from compressor to condensor and condensor to receiver drier, and drier. Ran it at least 4 hours idling, fast idle and drove it, cooling at 50 degrees. Driver took it out last night and I talked to him a while ago, said it quit again.



Truck has seperate units for cab and sleeper(evap and expansion valves) and the lines split to go to each unit. To me if 1 unit were to plug somehow, it should still flow through the other unit OK. The pressure switches should protect it also. I am thinking I will replace the last rubber line before they split(in case it is collapsing internally) and the temperature probes for each evaporator.



Sorry for the long post but if any one has an idea I am all ears. I am really stumped at this point, of course it works great in the shop.

Thanks for any help.

Matt

 

[mwilson]

I have a truck at work that losing freon, it appears to be out of the relief valve on the back of the compressor. It has done this at least 6 times, maybe more. Here are the details:

Truck is a 2006 freightliner columbia with a 60 series detroit, sleeper.



Original problem the compressor locked up and clutch was burned up, compressor was replaced and receiver dreir at the time, along with cab filters. System was basically full of freon when the first compressor was removed. After that it has been losing freon out of the relief valve. Tried recharging and locked engine fan in to run all the time. Then tried another compressor and problem continued. That compressor ending up locking up and burning the clutch up after 2 or 3 times being charged. Reinstalled the other compressor.



Tried overcharging the system to test the high pressure switches in the receiver drier to see if they were shutting compressor off at high pressure, they were working but replaced them anyway along with the relay for the compressor. Leaked out again, another guy charged it in the shop and the condensor started spraying out the front where the grille screen had rubbed it a little. Replaced the condensor and thought it may have been the leak and the fan was spraying the freon around. Lost freon again, yesterday I replaced both expansion valves(cab and sleeper) and hose from compressor to condensor and condensor to receiver drier, and drier. Ran it at least 4 hours idling, fast idle and drove it, cooling at 50 degrees. Driver took it out last night and I talked to him a while ago, said it quit again.



Truck has seperate units for cab and sleeper(evap and expansion valves) and the lines split to go to each unit. To me if 1 unit were to plug somehow, it should still flow through the other unit OK. The pressure switches should protect it also. I am thinking I will replace the last rubber line before they split(in case it is collapsing internally) and the temperature probes for each evaporator.



Sorry for the long post but if any one has an idea I am all ears. I am really stumped at this point, of course it works great in the shop.

Thanks for any help.

Matt

Is the fan still locked in manually???



If the fan is back on automatic control when the truck is idling in the shop with the A/C does the fan kick in and out as the system high side pressure rises and falls???



Give me the last 6 of the vin for two reasons, first to see if you have been sold the correct compressor and two to see what else it may have for controls. Did you purchase the compressor and dryer at a Freightliner dealer??



How much R-134A are you putting in it at the initial fill?? I can check that capacity by your vin as well.



Mike.

 

[mwilson]

Matt,



I just recalled where you work so I know what parts you are using. Those are good products, no worries.



I'd still like the vin to see what controls it has. After I get a little more info from you I'll call one of my A/C guys at work and run it by him.



Mike.

 

[mweiman]

VIN X27537



3. 75 lbs per the sticker on the truck



Compressors were from Freightliner dealer, part # off their invoice ABP n83 304543s, driers were MEI 7197 from Ryder Fleet products, All other parts were from Freightliner.



I just plugged the fan solenoid back in yesterday to run on auto, but it had been locked in all this time it has been acting up. It seemed to be cycling fine, it was staying engaged in most of the time here at the shop but it did cycle in and out. Radiator/ CAC/condensor(new) don't look plugged up. Temps were in the 90's.



It seems like they will go out in it at night and it will quit by that morning. I just ordered evap temperature probes and the rubber hose from the drier to where the lines split which will be the last rubber hose in the system to replace. My thoughts with the evap probes were that they are reading to high and not cycling the compressor out at night when it is cooler causing it to freeze/ice up back to the compressor. Just a guess though.

Thanks for your help,

Matt

 

[mwilson]

VIN X27537



3. 75 lbs per the sticker on the truck



Compressors were from Freightliner dealer, part # off their invoice ABP n83 304543s, driers were MEI 7197 from Ryder Fleet products, All other parts were from Freightliner.



I just plugged the fan solenoid back in yesterday to run on auto, but it had been locked in all this time it has been acting up. It seemed to be cycling fine, it was staying engaged in most of the time here at the shop but it did cycle in and out. Radiator/ CAC/condensor(new) don't look plugged up. Temps were in the 90's.



It seems like they will go out in it at night and it will quit by that morning. I just ordered evap temperature probes and the rubber hose from the drier to where the lines split which will be the last rubber hose in the system to replace. My thoughts with the evap probes were that they are reading to high and not cycling the compressor out at night when it is cooler causing it to freeze/ice up back to the compressor. Just a guess though.

Thanks for your help,

Matt

Just talked to a pretty good tech, we went over the Columbia A/C system. The relief on the back of the compressor is the only one in the system. So we think that the truck is building way too much head pressure.

The binary switch controls the low pressure cut in and out for the system plus commands fan operation when the high pressure point is reached.

HOWEVER there is no high pressure kick-out in the system. It will just keep running the engine fan with the compressor engaged assuming that it can compensate. So you have either an overcharge of R-134a or we are thinking that the clutch fan is not up to snuff. Even though it is engaging it could still be slipping.



The Cascadia's do have a high pressure cut-out but not the Columbia or Century Class models.





What is the duty cycle for the truck??? Loaded heavy, a lot of hills??? Slow heavy traffic speeds???



The compressor is weeping because that is the only way out for the over pressured R-134A.



Does that help??



Mike.

 

[mweiman]

I think there is some type of high pressure cut out switch. There are 2 switches in the drier. I overcharged the system by a pound and it would build to like 450 psi and kick out, when it dropped out so far it would kick back in and build right up and kick out. Cycling like every 5 seconds on/off. I overcharged it to see if it would kick out as I have seen mate trucks to this one be overcharged and do the same thing in the past. The truck pulls a 28 ft pup trailer delivering to gas stations so not overloaded by any means and mix of open road/city driving. Mostly smaller towns so it is not like it is sitting in traffic for hours. Like I said it seems like it will lose the Freon early morning before it has even got hot for the day. It hasn't worked for a full day in about 2 weeks. I just can't figure out what I could be missing.
Matt

 

[mwilson]

Could the fan control solenoid be sticking or defective???

 

[mwilson]

I've got another tech that I will talk to in the morning to verify or deny the high pressure cut-out. Curious about that.



I see that it has the Kysor fan clutch, still wondering if clutch facings are worn and it is not getting up to speed.



Mike.

 

[E7mack96]

I am gonna watch this thread as I work on these trucks every day. . I had one split the evaporator in half. . blew out the entire dash.

 

[E7mack96]

Hey i just had a thought... Is the drier in right? sometimes those dryers from Ryder fleet products have the decals on the opposite side and guys don't pay attention and install it backwards. I have caught a few of them in my shop. I always look for the "in" stamped in the side of the top and go with that.

 

[E7mack96]

Here is a pic of one that popped

 

[mweiman]

The fan solenoid has been unplugged/engaged up until yesterday, I had pulled on the fan and it seems tight. It also roars pretty good when engaged and I think high side pressures were 150-200 with it engaged. Not opposed to replacing it at this point though.



The switches on the drier are both 2 wire switches, 1 has about a 5" wire lead. Drivers have told me that they have heard it blowing off while sitting at an idle getting fuel so maybe there is some sort of airflow issue. I also need to try to find out engine temps to make sure it is not running hot. It won't be back until tomorrow afternoon and I may try to get this truck put on a night shuttle route so I have more time during the day to look at it.

Matt

 

[mweiman]

The drier is installed correctly with the stamped "in" on the inlet line, I have checked a couple times and it has been changed twice during this problem. I may put a freightliner one on it just because the 2 I put on were on the shelf for a while and were put in stock at the same time so possibly a bad batch. As for the evaporator I guess it is possible but in the back of my mind with the lines splitting off and going to separate expansion valves and evaporators I am thinking if 1 plugs it should still flow through the other loop of the system.
Matt

 

[E7mack96]

even though you have replaced most parts at this point, Were the evaps and lines flushed of debris at any point? (while the expansion valves were removed) also, with all the compressor changes, and component changes, has the oil in the system been adjusted accordingly with each compressor change?

 

[EMAC2]

even though you have replaced most parts at this point, Were the evaps and lines flushed of debris at any point? (while the expansion valves were removed) also, with all the compressor changes, and component changes, has the oil in the system been adjusted accordingly with each compressor change?

I agree with these thoughts. The only way to build excess pressure is to have a restriction in the system after the compressor but before any safety cut offs. Was the orifice tube or TXV changed after the compressor was replaced? Small debris will clog these devices in a hurry since there job is to "restrict" the flow and allow the expansion of the gas in the evaporator.

Not all A/C systems are designed the same, but usually if you have a high pressure safety device opening, you have a restriction or a weak safety "pop-off".

Cleaning the system is essential after a compressor failure as all manner of ground up particles get circulated throughout the entire system ("black death"). If it was not flushed and purged, then I suspect you have a "clog"... ...

 

[mwilson]

It sounds like Matt changed both expansion valves already. There is one for the cab unit and one for the bunk unit.



Matt,

You have replaced all of the rubber lines except for one. Did you check the hard lines for the sleeper unit A/C that run under the cab and bunk for obstructions???



There could also be a wiring issue, a bad connection from the high pressure switch. I am also wondering if the ECM is involved here. It is in charge of the engine cooling fan in regards to coolant temps. There is a temp sensor on the block but that information goes to the ECM. From there it goes to the cab gauge and to the fan control solenoid to apply the fan as needed. It is not unreasonable to assume that the ECM may make fan engagement decisions for the A/C as well based on input from the high pressure switch.

I will be calling the Bangor shop at 8. 00 today to see what else I can find for input.



I know that you are getting info from the driver (which can be a challenge) so did he happen to mention if the fan was engaged while it was blowing off R-134A while idling at the fuel pumps???



Mike.

 

[mwilson]

From the Service Manual... ... . the binary switch is in control of the high pressure cut-out. That makes more sense.







Binary Switch

Located on the liquid line from the receiver-drier, the

binary switch disengages the refrigerant compressor

to protect it from harmful operating conditions. It performs

two functions:

· If the refrigerant system pressure is too low,

the binary switch will keep the compressor

from operating. The switch disengages the

compressor when the pressure on the high

pressure side of the system falls to 27 to 35

psig (186 to 241 kPa). Normal compressor operation

resumes when the rising pressure

reaches 28 to 36 psig (193 to 248 kPa) above

the shutoff pressure. This occurs when the ambient

temperature falls to around 31 to 40°F

(–0. 56 to 4°C) or when refrigerant has leaked

out of the system.

· If the refrigerant system pressure on the highpressure

side increases to 427 to 484 psig

(2944 to 3337 kPa), the binary switch shuts off

the compressor clutch. Too much pressure

may be caused by excess refrigerant in the

system, or anything that causes poor condenser

performance, such as poor air flow

through the condenser. When the system pressure

has decreased to 313 to 426 psig (2158

to 2937 kPa), the compressor resumes operation.

NOTE: Since the binary switch is on the highpressure

side, the compressor may continue to

operate (trying to cool the cab) if most, but not

all, of the refrigerant leaks out of the system,

until the air conditioner is turned off or the vehicle

is shut down for a short time. Continuing to

run the compressor with a low charge can lead

to a lack of lubrication and high temperatures in

the compressor















Fan Cycling Switch

Located on the junction block liquid line, the fan cycling

switch sends a ground signal to the ECM (engine

control module) to keep the fan off and take

away the ground to engage the fan. The fan will

come on if refrigerant pressure is greater than 300 ±

10 psi (2070 ± 69 kPa). The fan turns off when pressure

drops below 250 ± 10 psi (1725 ± 69 kPa) and

the engine ECU timer (0 to 180 seconds) has expired



Mike.

 

[mweiman]

I don't know if they would know if the fan was engaged or not at idle. It would have been locked on at the time though. I plugged the fan solenoid back in Monday when running it here at the shop to see if it was working OK and it seemed fine so I left it plugged in. I checked all lines for obstructions, but I think I will flush the system again and catch the solvent coming out to see if there is anything in it. I have changed the amount of oil charge with some of the component changes because I suspected the first guy who changed the compressor may have put too much in, same results every time.

I think fan control is an output of the ecm and the high pressure switch is an input. I will try monitoring the a/c system with servicelink also. Not for sure about this one but I just did some google research and it looks like the compressor relief valves are set for about 550-600 psi.

 

[mwilson]

I just checked in my parts system as there was a switch connection issue rattling around in my head from past experience. According to our parts notes in the system when I enter the part number for the binary switch there is a replacement harness for that switch that we sell once a month or so which tells me that they do give some trouble. A bad connection there could prevent the high pressure cut out from functioning allowing sky high system pressure.



The part number for that harness is A06-32756-001.



Mike.

 

[mweiman]

NOTE: Since the binary switch is on the highpressure

side, the compressor may continue to

operate (trying to cool the cab) if most, but not

all, of the refrigerant leaks out of the system,

until the air conditioner is turned off or the vehicle

is shut down for a short time. Continuing to

run the compressor with a low charge can lead

to a lack of lubrication and high temperatures in

the compressor

There will only be about . 2 pounds or so of freon left in the system when it comes in, which I guess is even more puzzling if it is coming out the relief valve. There is always freon/oil around the relief valve and you can see it has sprayed all over that side of the engine, all the hoses are dry though. It sure would be nice to see it act up with guages on it.



Matt