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Air pressure runs to 150


Coenut

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While driving a r model home the air pressure gauge started to climb right to 150 psi. For some time the truck was spitting at 120. Then it stopped and it would climb right to 150 psi. I changed the governor and it was fine for 10 miles or so. It now climbs right to 150psi. I was bob tailing and ran with the trailer valve open. There's a finned canister behind the cab. It has air in and air out along with some wires all cobbled together. Any info or ideas would be greatly appreciated.

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There are 3 ports on the air governor- exhaust, signal and unloader. The signal line is from the wet tank, its the air tank fed directly from the air dryer. When the pressure in the wet tank reaches 120 psi the air governor sends an air signal to the unloader port which goes to the air compressor head and dryer. If air continues to build to 150+ psi then either the signal line from the wet tank is plugged or the air governor is bad. On the older R models the signal/unloader lines were usually stratoflex line. It could be coming apart inside the line.

To test the air governor install a test gauge inline or into one of the "Signal" ports on the air governor (gauge should go up to at least 150 psi). If the test air gauge is not showing the same value as your dash air gauges then the line is plugged from the wet tank. If the air psi is the same as the dash gauges move the test gauge inline or into a "unloader" port on the air governor. There should be no air psi on this line until at least 120 psi (depends where the air governor is set). Once that pressure has been reached then there should be air pressure (same as system psi). If this never happens then you have a bad air governor. Make sure there is no oil or water in the signal line, That can destroy an air governor in no time

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I have almost the same issue with one of my R688. The pressure goes up to 150 pci and than some protection valve opens in the air dryer (or somewhere below the chassis) and drops the pressure to 120 psi. I took the governor apart and than swapped it with the other off the second truck wich worked correct but had no good result. Haven't go on the fight path already yet, need to collect enough of info to start.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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If it's below freezing ambient in your area I would find a quart of airline anti freeze and take the air intake line off that runs to the compressor and , with the engine running/compressor pumping slowly pour about half of a quart into the intake line, wait a minute and repeat with another half quart....this should open any frozen lines and let the system operate as designed. If this doesn't work, dig deeper, but for my money....I'd try this first.

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When this was happening it was above 40f.

Chances are it wasn't frozen then, at the very least you should find an relief valve on one of your air tanks (mines on my wet tank) that won't let the system pressure build beyond a set point (Usually 20lbs. or so0 above the governor cut off) so you have multiple malfunctions....

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  • 6 years later...
3 minutes ago, Joey Mack said:

my question is.... how do you find an old post?  however I have typed it in to google and it will show a BMT listing... maybe thats how???   jojo

Probably, and I’m gonna guess he never comes back.  

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4 minutes ago, Joey Mack said:

my question is.... how do you find an old post?  however I have typed it in to google and it will show a BMT listing... maybe thats how???   jojo

i find alot of old post by going to whos on line -then see what the guest are viewing. that turns up past history of topics. becomes a situation when finding yourself wanting to respond to old old topics

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I think a filter or a "Flag" on post's that are a year old and older would work,, no need to delete them just inform the viewer that they are older post's...  jojo

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3 minutes ago, Joey Mack said:

I think a filter or a "Flag" on post's that are a year old and older would work,, no need to delete them just inform the viewer that they are older post's...  jojo


Right, just lock them out. I also think we need to start a thread with parts numbers/diagrams 

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