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Discussion Starter · #1 ·
Let me preface my question by saying that I do not have any air leaks, at least outside of the valve block. Here is the issue: when I increase the ride height (with the inhibit switch on), the compressor runs as expected. However, it will stop when the pressure in the systems reaches around 80 psi. In a few moments, it will run again and go to 110 psi, and switch off; then switch on again and go to 120 and switch off; finally it will make it to 140 (close to the correct "off" value) and switch off and not come back on again.
OK, sounds like a pressure switch, but the strange part is that the behaviour is essentially exactly reproducible! If I decrease and increase the ride height, it will go through the same sequence again! I would not expect a bad switch to behave reproducibly.
I have ordered a new pressure switch, and in the absence of any information I will replace it. Any chance of anything else? I do have a replacement valve Driver, but I cannot see how this could be involved. As I understand the system, only the pressure switch controls the compressor on/off. Could there be any problem in the valve block itself?
Thanks for any input!
Wayne
 

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Problem is more likely the temperature sensor in the pump. Pump runs, pump gets hot, switch opens to switch the pump off, pump cools down, sensor resets so pump runs again until it gets hot and cuts off again and so on.
 

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Discussion Starter · #3 ·
Thanks Richard; interesting idea. The sensor would need to be faulty since the compressor is cool to the touch, no where near the 170 deg cutoff. I assume that this is not repairable, so I would be looking at a replacement pump.
Wayne
 

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Discussion Starter · #4 ·
Richard
I think that I can test your suggestion with Nanocom. During the pressure cycling on and off on the way to 140 psi, the pressure switch, since it remains in the "open" state even when the compressor stops running at one of the intermediate pressures. It goes "closed" when 140 psi is finally reached. On the other hand, the thermal switch stays in the "normal" state at all times. Maybe the Nanocom is not reliable reading the thermal sensor, but if it is OK, then there is still another possibility somewhere.
Wayne
 

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I was checking the EAS on another car last week and noticed that the pump was cutting off even though the Nanocom was reporting that the pressure switch was open and the thermal switch was normal. It might be something to do with the slow response of the Nano to a momentary change of state? You can hear various solenoids clicking open but the Nano doesn't show this as they are too quick for it to register. Maybe the thermal switch is opening briefly and there is some sort of delay built into the ECU so it doesn't restart immediately? As a test you could put a jumper wire between the Orange and Black wires on the pump, if it doesn't cut out it is the thermal switch.
 

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Discussion Starter · #6 ·
Richard
You are correct! When the thermal switch opens, it breaks a ground to the ECU, signalling a compressor shut off. I monitored this directly and sure enough, when the pump stops the ground is broken corresponding to opening of the thermal switch. Nanocom just does not find it, maybe a response time as you suggest.
Thanks, I just ordered a new pump.
Wayne
 

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2002-2005 Range Rover MkIII / L322
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Yes, the temp sensor was my first thought, too.

Keep the old pump, you might need it for spares one day. :)
 

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The pump sensor wire is connected internal with a PCB mounted crimp that often goes intermittent. Hence pump runs until the wire is loose even before max temperature is reached. I have fixed several pump issues by simply soldering the terminals on the PCB.

While you have the pump apart, might as well do the piston ring refurb as well, unless it's been done recently.

FYI, the ECU will occasionally stop the pump to adjust the height, even if the tank is not yet full, but at least you found the intermittent sensor is probably your issue.
 

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Discussion Starter · #9 ·
Thanks for the information P38arover.
I may be in a vast minority, but I find the EAS on the p38 to be a remarkable and brilliant piece of engineering. I love this thing. I bought Emma new in 1999 and only 22 years and 220,000 miles later did the pump finally give up, and in the meantime the suspension has worked very well and never stranded me. All I have done is to replace ride height sensors all around and air springs with Arnott gen III twice. I consider that pretty reliable.
Wayne
 

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I'd say you are in the vast majority, the vocal minority that don't understand the EAS always seem to be the ones that shout the loudest, the rest of us just carry on without issue. Your Arnotts don't seem to last that well. I bought my car when it was 11 years old with 205k miles on the clock and still on the original, but leaking, Dunlop air springs. I fitted a set of Dunlops and after a further 13 years and 230k miles, they are just starting to look like I may need to replace them in the next year or so. You only need Gen 3s if you are lifting the suspension, they give nothing if you keep the heights standard.
 

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Discussion Starter · #11 ·
My first set of Gen IIIs lasted 7 years and I probably changed then prematurely; they were not leaking but the cracks in the rubber around the base made me nervous as a novice with air springs. I just did not want to be stranded in the outback of Death Valley where Emma spends considerable time. My current set is 9 years old. They are not yet leaking, but I can see some small cracks in the rubber which now make me less nervous. I suspect they will go a while more. Arnott assures me that the failure will not be catastrophic, they will just start leaking slowly. There have been catastrophic failures in Gen IIIs reported due to a defective band, but that happened immediately upon pressurization and is rare.
I went to the Arnotts after multiple events where the Dunlops simply did not seal well. They were replaced under warranty by the dealer and still a problem. The Gen IIIs have treated me well and they have a no-questions-asked lifetime warranty which they honor. Of course I need to do the labour of installation!
Wayne
 

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Discussion Starter · #12 ·
OK guys
I just received a brand new, in the box, Dunlop replacement compressor. Amazingly, it behaves exactly as described for the one I replaced, ie, it takes 4 tries to get to the 140 lbs shut off, and then is fine until I raise the vehicle and pressure is required, then the cycle starts all over again.
Is it likely that the new pump has a bad thermal relay? Back probing the connector or wires to jumper the orange and black as suggested by Richard to troubleshoot is not so early without doing some damage, which of course, would not be good if I attempt a return.
For reasons that I will not explain, I ordered by mistake a second compressor due tomorrow. I will install and see.
Is it at all possible to be a pressure switch?
This is becoming tedious.
I did pull the back off the old compressor (without multiple hands I will never get the brushes back in position!). Pwood999 is the crimped wire you mentioned the orange wire?
Wayne
 

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Discussion Starter · #13 ·
BTW, any tricks to getting the motor brushes back in place around the armature while replacing the end cap with the circuit board?
 

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I forgot how exactly I did it in the past, but the key is to find a way to lock the brushes in place while the contraption you use is thin enough and sturdy enough so that you can almost replace the end cap fully. Then, you pull the contraption out, seating the brushes. I haven't fiddled with an EAS pump in the last few years, so don't quite remember how I did it, unfortunately.

Hopefully, others chime in to give you better guidance.
 

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Look for the loose fibre ring that sits between the PCB and the bearing. Many people wonder what this is for, but this is there to hold back the brushes during assembly. It's not easy to get it in the right place if the brushes are worn though.

Alternatively, I have either used thin string to hold them back until the end cap is almost in place. or used the flexible wires on the brushes to hold them back. Then pull out the string or release the brush wires once the brushes are aligned with the armature contacts.
 

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Discussion Starter · #16 ·
Ahhh, the thin fiber ring! Yes I wondered what that was for. I will give it a go or use a string.
Thanks!
Wayne
 

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I have tied the brushes back with thread. You slide the armature far enough on to hold the brushes and then cut the thread and pull it out.
 
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