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Oilless Compressor OF45150A Problem

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  • #16
    Yes, the max pressure is 150 psi.

    No, there is no situation where the relief valve releases air unless I pull on the wire to manually release it.

    The relief valve wire requires a gentle tug to get it to release air - u can see that in the video I posted.

    So I think this argues for changing the switch assembly as the first thing to do?

    Thanks again.


    • #17
      I watched the video. Yes, the relief valve seems OK. That's a significant leak. You can't
      find where that originates from? If you could it would certainly help locate the problem part.
      "It's a table saw, do you know where your fingers are?" Bob D. 2006



      • #18
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        The air is escaping from under the switch cover - from the metal tab between the two posts (circled in yellow). This is where the air is coming from. It must be a valve of some sort because if you press on it, or the small black button on top of the housing (circled in yellow) the air is released from the tank.


        • #19
          That is the pressure switch. The two threaded rods that are painted green are
          the trip (motor ON) and reset (motor OFF) adjustments, assuming the switch is
          direct acting or Close Decreasing and Open Increasing.

          I've seen switches like that with a bad bellows. They can get a crack in the folds of
          the bellows and won't leak excessively below a certain pressure until you touch them.
          I'd be willing to bet that's what's happening here. Don't know if your switch is a bellows
          or a diaphragm type switch without more information. Does the underside of the switch
          cover have a label on it.

          Can you show us a side view of the switch that includes the tubing that connects to the
          tank. The switch is probably mounted right on the tank though with a short pipe nipple.
          "It's a table saw, do you know where your fingers are?" Bob D. 2006



          • #20

            Are you sure it is the safety relief valve that is popping off on reaching maximum discharge pressure OR are you hearing the unloader valve, which triggers when the pressure switch stops the compressor once the maximum set-point of the pressure switch is reached? (That "set-point" is the "maximum discharge" rating of the compressor.

            Safety relief valves are usually set about 10 psi (or a maximum 15% over the rated discharge pressure...whichever is less!) higher than the maximum discharge pressure setting and is there to trigger relief when the maximum pressure is surpassed because the pressure switch malfunctions.

            Are we talking about the same thing... "relief valve" vs "unloader valve vs "safety valve"? Perhaps I've misunderstood you or we have our nomenclature different. What I see ShreibDave doing is pulling the cable on the safety relief valve, which of course will dump the pressure. That however should not go off at the maximum discharge pressure ("maximum set-pressure of the pressure switch). For example, on this particular compressor, the maximum discharge pressure should be 150 psi, so the safety relief valve should blow at 160 psi maximum. Unless of course it too is defective.

            I'm not sure what stamping may be on the tank itself, if any. But on an ASME tank there is a maximum allowable working pressure (MAWP) stamping. The compressor's rated maximum operating pressure or maximum discharge pressure, will be less than the MAWP. So on this particular compressor the discharge rating is 150 psi, the safety valve would be about 160 psi and the MAWP of the tank slightly higher. Neither the discharge and especially the safty relief valve should be higher than the MAWP of the tank. The safety relief valve is not supposed to trigger upon reaching the maximum discharge/operating pressure.

            Last edited by CWSmith; 09-24-2019, 07:35 PM.


            • Bob D.
              Bob D. commented
              Editing a comment
              I think we are talking about the same thing. Yes, when he pulled the cable and caused the relief valve to vent that would be at a slightly higher pressure than the 150 PSI rating of the compressor. Which is of course why it required that additional effort on his part to cause it to vent. I agree with your statements on the MWP of the tank and the set pressures of the pressure switch/unloader valve and safety relief valve.

              Bottom line is the pressure switch appears to me to be the bad egg here. The manual lists a pressure switch and a unloader valve, which not being familiar with this piece of equipment (since I don't have one) makes me think they are two separate components. Is that not the case?

              The parts list on the RIDGID site gives this as the pressure switch, but it does not look like the switch in his photo, so this may be the recommended replacement.


              Last edited by Bob D.; 09-25-2019, 07:10 AM.

            • CWSmith
              CWSmith commented
              Editing a comment
              "Bottom line is the pressure switch appears to me to be the bad egg here. The manual lists a pressure switch and a unloader valve, which not being familiar with this piece of equipment (since I don't have one) makes me think they are two separate components. Is that not the case?"

              That may well be the case here as I looked at the link you provided and that particular model prefix has three different models, only one of which has an integral unloader, Note my post below... but note that all three of those switches are factory set at an "On/Off" of 80/100 psi !

              I don't have that compressor or the manual, so I don't know about the "unloader"... apparently, as you mention it may be separate.


          • #21
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            Condor MD11 Switch
            "It's a table saw, do you know where your fingers are?" Bob D. 2006





            • #22
              The part number on my switch cover is teh same as the part number on the one above. The cover looks the same but the switch looks a little different. I am going to ask them whether my cover will work with this switch. Thanks and I will report back when I receive the part.


              • #23
                Yes, I saw that all three models were listed a 80/100. I didn't look to see if they have another model rated for 150 PSI.

                Whatever cover comes with the replacement switch is the one to use.

                As I said in the beginning these parts are not that expensive and since all three are currently available I would get them all even if you don't put all three in right now. Next month, next year they may be impossible to find, who knows.
                "It's a table saw, do you know where your fingers are?" Bob D. 2006





                • #24
                  For whatever it's worth, I wrote this at 11:45 this morning and thought I posted it. Obviously not, as I just noted that it saved automatically and the site asked if I wanted to discard or post... sorry! I agree will BobD's previous 2:26 post.


                  OK, now I'm really confused. Looking at the picture it says the PS switch is an "11EA" and you say that part number is the same as yours. But, when I look at the Condor product page that BobD linked to, I see three different "11EA" pressure switches listed; two without and one (11EA2E) with an unloader valve. But what raised my question is that all three have the same on/off pressure settings of 80/100; NONE are factory set for 150 psi.

                  So the question, did Ridgid use this lower model pressure switch and factory set it for the higher "OFF" setting of 150 psi ?

                  And, not seeing the full model number, is the "unloader" included in this switch or is it a separate component?

                  Personally, I've never liked the idea of an adjustable pressure switch on a consumer grade compressor, as some nut is just liable to adjust the pressure setting higher, replace the safety relief valve and put the whole thing in jeopardy. That of course is just my opinion, but what a liability for a manufacturer to have.

                  Last edited by CWSmith; 09-25-2019, 06:53 PM.


                  • #25
                    I already ordered it so we will see. One question I will likely have is how to remove the two plastic tubes that are attached to the underside of the switch. One goes to the gauge cluster and seems to have a threaded fitting on both ends. I guess I can get a wrench on the fitting with the switch detached from the tank. The other tube has a black fitting at the switch that is not threaded - its seems to have a little set screw on the side - unreachable with the switch mounted on the tank. Hopefully with the switch hanging loose of the tank that set screw releases the fitting.

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                    • #26
                      Coming from the original switch was this hose with the rt angle connector on it. The new switch came with a new connector but no hose. And the design of the connectors are different. The old connector/hose assembly wont go into the new switch.

                      So how do i disconnect my old hose from this connector so that i can reuse the hose with the new connector?

                      Thanks Click image for larger version

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                      • #27
                        They're known as 'Push to Connect' or 'quick connect' fittings, name will vary with manufacturer of course.

                        A quick search on the web found dozens of YT videos showing how they work. Your old fitting probably needs a tool to release it, but you can most likely use a screwdriver if you are careful.
                        If you do nick or damage the tube when removing it, you should cut it square with a razor knife, don't use wire cutters or scissors as they will crush the tube and not make a clean, square cut.

                        Actually you probably don't have to worry about the old fittings, just use a razor knife and cut as close to the face of the old fitting as possible UNLESS you don't have enough slack in the tube. Make sure the tube will reach when you have the new fittings installed and don't forget to allow for the short section of tubing that gets inserted into the fitting.


                        "It's a table saw, do you know where your fingers are?" Bob D. 2006





                        • #28
                          Thanks Bob! Took me less than 1 second to get it apart once I knew what the mechanism was. Pushed on the outer ring with the side of a small open end wrench and the tube popped right out.

                          On an unrelated subject - I am having a heck of a time determining what size wrenches to use on this thing. Neither metric nor imperial size wrenches fit perfectly. I've taken to using an adjustable crescent wrench on many of the fasteners. And advice on that? I had to pull the motor and gauge cluster off in order to get at some of those fasteners.


                          • #29
                            Are you talking about getting a wrench on the body of the fitting? Since there are no compression nuts that's all I can think of. They body of the fitting may have flats on it which may not be an exact imperial or metric size, so your adjustable may be your best choice.
                            "It's a table saw, do you know where your fingers are?" Bob D. 2006





                            • #30
                              Well ... got the new switch installed and it performs exactly the same. Builds to 150, lets air out from under the switch cover down to 125 then hums and refuses to restart. Unplug and replug and it will repeat the above sequence.

                              If i were to swap another part out, what would it be?