[Dudeonthenet]

Hi, My 2004.5 had a PacBrake on it when I bought it. It worked fine for several years but recently quit. I tow an RV with this truck, and the PacBrake is very helpful, so I need to fix it. I don't have any experience with these exhaust brakes so am trying to figure out how to diagnose and repair it.

Below are two pics of it. The first pic is of the most visible part of the PacBrake. It's a 150 psi compressor, Model # 10143

The second pic is of the small part on the front of the PacBrake in the first pic.
First question is, what is this part called and what does it do?
Second question, you can see in the second pic that I can easily pull the part up and out. Is it supposed to be that way?

I found an inline 30 amp fuse to the PacBrake, and the fuse is still good.
Any advice on how to proceed to diagnose and repair this PacBrake would be much appreciated!



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[brooklyn 12]

That is the solenoid,IIRC, and the nut that is supposed to be on the threaded end, is missing. That's why you can move it up & down. Exact same thing happened to mine & I ended up buying a new solenoid from PAC, which fixed my problem (of it not working). I wondered later if I had just got a nut & put it on, would it have fixed it?

 

[06cummins1974]

You will probably need a new solenoid. The solenoid on mine had a O-ring crack in it allowing air to leak by. Since the air was leaking my compressor was running constantly and burnt it up. I bought my new compressor from thoroughbred diesel and the solenoid from CPP diesel. Does your compressor run? Mine would run but wouldn’t build any pressure.

 

[Dudeonthenet]

You will probably need a new solenoid. The solenoid on mine had a O-ring crack in it allowing air to leak by. Since the air was leaking my compressor was running constantly and burnt it up. I bought my new compressor from thoroughbred diesel and the solenoid from CPP diesel. Does your compressor run? Mine would run but wouldn’t build any pressure.

Thanks. Right now, no, the compressor doesn't run. But could that be because the solenoid is broken? Do you think that I should try to hot wire the compressor to see if it runs? Or would it be better to first replace the solenoid and then see if the compressor will run?

 

[brooklyn 12]

^^^^ I called PacBrake directly to trouble shoot what was my problem & they were 100% helpful/friendly. My compressor would also run but wouldn't build any pressure.

 

[06cummins1974]

Thanks. Right now, no, the compressor doesn't run. But could that be because the solenoid is broken? Do you think that I should try to hot wire the compressor to see if it runs? Or would it be better to first replace the solenoid and then see if the compressor will run?

You could do it either way. I would just replace the solenoid first and see what it does.

 

[Dudeonthenet]

You could do it either way. I would just replace the solenoid first and see what it does.

Thanks, yeah, that's what I decided to do. I already ordered a new solenoid, so when that arrives, I'll install it and see if the system will work and go from there.

 

[CTD NUT]

That solenoid is for exhaust brake activation has no bearing on compressor operation. I agree that the solenoid does need to be replaced but it is not going to help your compressor issue.

Assuming the relay and fuses are good, troubleshoot the compressor by testing for power at the compressor and working your way backwards from there. If there is no power at the compressor motor move up stream and keep checking for power. I have had Pacbrake systems for 14 years and there are a few common failure points from an electrical standpoint. The most common one for me was the pressure switch. I have chewed through a few of them over the years. They can seize open or closed. I have also chewed through a few compressors until I ditched the engine mounted Pacbrake unit and went to a larger remote mounted Viair unit.

From my own experience, the compressor motor might be shot or the pressure switch is seized. A couple of minutes with a test light will confirm either of those issues.

 

[TRP45ACP]

My pacbrake failed the other day, ordered a new compressor (installed yesterday) and it is working fine. As mentioned earlier, the engine mounted 325 compressor unit is weak, has a 30% duty cycle and produces 1.1 cfm. Pacbrake offers the 625 compressor which has a 100% duty cycle with 3/4 hp and significantly more cfm but it has to be mounted elsewhere like frame rail due to its much larger size. It also has a different solenoid set up, potentially wiring (not sure). My friend is on his 3rd 325 compressor. Depending on use, they last about 3 years. For simplicity, went with another 325 this time, $150 on Amazon. Also, the pressure switch can be problematic. Pull the output airline from compressor while running, is it weak? If so, my money is on compressor. They are subject to a great deal of heat due to their work load and mount position. Good luck

 

[Dudeonthenet]

Thanks much to CTD NUT & TRP45ACP for your troubleshooting tips.

I did some further troubleshooting after installing a new solenoid. I don't know where the relay is to test it, but there is power to the compressor when the engine is running. It does build some pressure at the air quick connect with the engine running, but not very much pressure, certainly not enough to easily air up a small tire, which I did do once a long time ago. Should there be a lot of pressure there? And if the compressor is the problem, could it still be producing a modest amount of pressure, but not enough to run the PacBrake system?

How would I test the pressure switch?

Thanks again.

 

[CTD NUT]

So, you have power to the compressor AND the compressor actually functions. There is no point pursing other electrical issues at this time until you verify a couple of things.

First, does the compressor ever shut off? You have a 1 gallon air tank that the compressor fills. It should take a minute or so to fill it and then the compressor should shut off at the set pressure of the switch. Turn the ignition on (not the engine) and see if the compressor does indeed cycle and shut off. Put a pressure gauge on it and check to see what the operating pressure is like. If it does not cycle and runs continuously and never gets up to pressure, one of two things is happening - the pump side of the compressor is shot or you have an air leak somewhere. I'm betting on an air leak.


If the compressor does cycle and shuts off, what is the pressure? If the pressure is very low, the pressure switch is shot. If the pressure is fine and the brake does not actuate, you likely have an issue with the solenoid. That is really the only thing that can stop the pneumatic side of the brake from working if you have good air pressure.

 

[Dudeonthenet]

So, you have power to the compressor AND the compressor actually functions. There is no point pursing other electrical issues at this time until you verify a couple of things.

First, does the compressor ever shut off? You have a 1 gallon air tank that the compressor fills. It should take a minute or so to fill it and then the compressor should shut off at the set pressure of the switch. Turn the ignition on (not the engine) and see if the compressor does indeed cycle and shut off. Put a pressure gauge on it and check to see what the operating pressure is like. If it does not cycle and runs continuously and never gets up to pressure, one of two things is happening - the pump side of the compressor is shot or you have an air leak somewhere. I'm betting on an air leak.


If the compressor does cycle and shuts off, what is the pressure? If the pressure is very low, the pressure switch is shot. If the pressure is fine and the brake does not actuate, you likely have an issue with the solenoid. That is really the only thing that can stop the pneumatic side of the brake from working if you have good air pressure.

Thanks for those detailed instructions, very helpful. I turn the switch on, the compressor cycles on, but never shuts off. So I used a leak test solution (few drops of dish detergent in water in a spray bottle), and couldn't detect any leaks at any of the various air hose connections. And it seems to be building up even less pressure than it was when I was checking air pressure (without a gauge at that time) at the air quick connect a couple of days ago!

When the compressor is running with an air pressure gauge at the air quick connect, it moves the needle, but very very little. As I said, less pressure generated than when testing it a couple of days ago, now pressure generated seems to be declining to almost nothing. Since I can't detect any air leaks, I'm thinking that the pump side of the air compressor is bad and getting worse. So I'm thinking that it's time for a new air compressor. Would you agree?

 

[CTD NUT]

Yes, I would agree. No, leaks, no pressure build up and the compressor does not cycle and never shuts off - compressor is shot.