freightliner columbia A/C losing freon out relief valve

[mweiman]

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

Does that harness go from the 2 switches at the drier up to a large firewall plug and also split and run over to the driver side? Electric horn on it possibly. I just looked at a Columbia day cab on their lot, it had a part # on the harness I just described of a06-48416-000.

Thanks,

Matt

 

[mweiman]

Found the problem, wasn't the blow off valve after all. I will explain more when I have more time.

Matt

 

[mwilson]

Found the problem, wasn't the blow off valve after all. I will explain more when I have more time.

Matt

Looking forward to what you found. .



Mike.

 

[mweiman]

Truck is in the shop running and cooling again, hopefully this is the end of it.



I am starting again from the beginning:

truck originally had the A/C quit about 2 weeks ago, I drove it over here and did a visual inspection and found the compressor clutch burned up. The other guy here just went through our company a/c training so I had him look at it(he's actually supposed to be our truck fueler but we are a 2 man operation right now so he is in the shop 80% of the time). Anyhow I wanted to see him diagnose it, and try to get some use out of his training while it was still fresh. So he replaced compressor and drier and problem with blowing out freon started, it had most of a full charge with the original compressor. Anyhow after happening a few times he replaced the compressor again as we thought maybe the relief valve was defective. I noticed at one point that instead of reusing the torx head bolt to hold the lines to the compressor he had used the bolt that came with the compressor holding the plastic caps on it to seal it. At the time I just figured he dropped the original bolt and couldn't find it back. When the 2nd compressor locked up I figured it wasn't a compressor problem and put the first replacement back on. I checked to make sure the bolt would go all the way in by hand and it did, I was thinking it might not be getting the lines tight enough before it bottomed. I also added a lockwasher to it just in case at one point. I was still suspicious about that bolt today and even more when I noticed a vacuum hiss as I took the bolt loose. Here is what I found:

The correct bolt should only be about the length of the threads on this one that comes on the compressor.

Notice how you can see through the bolt hole between the line ports.

I can't believe after all the time that was spent watching this thing here in the shop not even a hint of a leak showed up. Every time the truck went out the a/c wouldn't last 5 hours and it would have freon sprayed all over that side of the engine. I am going to have a bruise on my forehead from slapping it!

Thanks Mike and everyone for your help and ideas. It is always good to have a place to turn when you have a problem you can't figure out.

Thanks again,

Matt

 

[mwilson]

WOW!!!



No wonder you were scratching your head. You did well to find it that quickly.



Speaking of things that make you scratch your head. .



We sold several M2 trucks to the local utility company. 6. 7 Cummins with an Allison Transmission. They have had these trucks for at least 2 years.

One came in last month with a complaint of the transmission getting hot (they have trans temp gauges from the factory). Tech crawls under the unit and decides to inspect the transmission cooler lines and cooler.

Guess what..... there were not any lines to be found. Neither the pressure or the return lines were there.



Upon further inspection found the cooler ports in the radiator still plugged with the plastic shipping protectors that the radiator had in it when it was shipped to the truck plant.



Upon even further inspection he found that the plastic shipping plugs WERE STILL IN THE ALLISON COOLER PORTS ON THE TRANS BODY ITSELF... ...



So those plastic plugs withstood the pressure and heat generated by that transmission for over 2 years. I would not (with my luck) have been able to drive something like that 10 feet without all Hell breaking loose.....



The truck was supposed to have the cooler lines, they just got missed when the truck was assembled. They were in the build record and parts listing, just never got put on.



Mike.

 

[mweiman]

That is impressive about the transmission plugs, I guess it's one of those things that would look normal enough most people who crawl under the truck wouldn't think twice.

Using the wrong bolt on that compressor was an honest enough mistake, it sure feels good to finally find the problem though. At the same time was also fighting an 8600 International that was cooling but only to about 70 degrees and the compressor was cycling in and out. System is controlled off of 2 thermistors giving input to the electronic systems controller. The inlet thermistor ground wire had a bad spot causing a high resistance reading which the ESC converted to colder temp(less than 24 degrees) and cycled the compressor out.

Probably the trickiest 2 a/c problems I ever had or at least that I can remember right now.

Matt

 

[Derrick Lucas]

Found the problem, wasn't the blow off valve after all. I will explain more when I have more time.

Matt

I’m having the same problem so to fix it you replaced the compressor and used a shorter bolt to hold the line to the compressor

 

[BigPapa]

I’m having the same problem so to fix it you replaced the compressor and used a shorter bolt to hold the line to the compressor

This thread is 11 years old and mweiman isn't a registered user anymore, hasn't been here since October '23.

 

[Derrick Lucas]

This thread is 11 years old and mweiman isn't a registered user anymore, hasn't been here since October '23.

Ok thanks I was just trying to see exactly what did he do to fix the problem because I’m having the same issue

 

[mcenevil]

Ok thanks I was just trying to see exactly what did he do to fix the problem because I’m having the same issue

Did you figure it out? Im having the same issue.