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Thread: SLS Compressor over active?

  1. #1
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    SLS Compressor over active?

    Hi guys,

    My '99 D2 V8 had spat out another SLS compressor, the failure stemming from water ingress into the motor causing the brush holders to rust away. So having read about replacing the wabco compressor with aftermarket types I happened to have a brand new reasonably sized tyre compressor sitting around which was duly installed into the rear of the disco. The original motor supply was extended to activate a new heavy duty solenoid inside the car which then supplies the compressor motor through suitable cables direct from the battery. The air supply goes back into the original valve block which is still in the original position. Works great and much faster than the original pump.

    However the problem is this. When I drive the car, stop for traffic lights etc, then drive off the compressor pumps away for roughly 10 seconds then stops. Next set of lights the whole thing happens again. But it will also pump air even if I only drive a couple of metres then stop. So the process is, drive, stop & count to 15, drive 2 metres & compressor starts, stop the car count to 15, drive 2 metres & compressor starts etc etc etc. It will do that process all day long. I've also driven long distance out of town, stopped for an intersection, drove off and the compressor gives a roughly 10 second burst of air. I've also noticed that when I get home and get out to open the gate, the exhaust solenoid dumps a very brief amount of air. Of course when I drive down the driveway the compressor has also started up. I don't know if this happens on the road as I've never heard it happen.

    There are no leaks that I'm aware of. The car can be sitting parked up for ages (read weeks) and does not loose height. It also got new airbags last year.

    Cheers, James NZ

    Compressor.jpg

  2. #2
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    Quote Originally Posted by James NZ View Post
    Hi guys,

    My '99 D2 V8 had spat out another SLS compressor, the failure stemming from water ingress into the motor causing the brush holders to rust away. So having read about replacing the wabco compressor with aftermarket types I happened to have a brand new reasonably sized tyre compressor sitting around which was duly installed into the rear of the disco. The original motor supply was extended to activate a new heavy duty solenoid inside the car which then supplies the compressor motor through suitable cables direct from the battery. The air supply goes back into the original valve block which is still in the original position. Works great and much faster than the original pump.

    However the problem is this. When I drive the car, stop for traffic lights etc, then drive off the compressor pumps away for roughly 10 seconds then stops. Next set of lights the whole thing happens again. But it will also pump air even if I only drive a couple of metres then stop. So the process is, drive, stop & count to 15, drive 2 metres & compressor starts, stop the car count to 15, drive 2 metres & compressor starts etc etc etc. It will do that process all day long. I've also driven long distance out of town, stopped for an intersection, drove off and the compressor gives a roughly 10 second burst of air. I've also noticed that when I get home and get out to open the gate, the exhaust solenoid dumps a very brief amount of air. Of course when I drive down the driveway the compressor has also started up. I don't know if this happens on the road as I've never heard it happen.

    There are no leaks that I'm aware of. The car can be sitting parked up for ages (read weeks) and does not loose height. It also got new airbags last year.

    Cheers, James NZ

    Compressor.jpg
    I've had similar issues with just the standard sls compressor, I think it turned out to be a dodgy height sensor/ plugs, the compressor would overshoot the required height because of the sensor and then be forever adjusting, is it possible that the compressor is too fast for the system?

  3. #3
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    The SLS will adjust everytime you get in or out... 😉
    "How long since you've visited The Good Oil?"

    '93 V8 Rossi
    '97 to '07. sold.
    '01 V8 D2
    '06 to 10. written off.
    '03 4.6 V8 HSE D2a with Tornado ECM
    '10 to '21
    '16.5 RRS SDV8
    '21 to Infinity and Beyond!


    1988 Isuzu Bus. V10 15L NA Diesel
    Home is where you park it..

    [IMG][/IMG]

  4. #4
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    I'm not sure that those tyre inflators have a built in non return valve cos the non-return is within the connection pipe with the gauge on it...so insert a push fit one way valve on the feed pipe which goes to the valve block cos the original compressor has one for the case the valves don't close 100%, worth a try to rule out a "back-leak" through the compressor when it's not running
    Discovery Td5 (2000), manual, tuned

  5. #5
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    Thanks for he replies guy. To answer the questions -

    I have new spare height sensors so will give them a go, but will test the original ones first.

    Sierrafery. I forgot to mention that I did fit a non return valve in the air supply line close to the original valve block when I did the conversion.

    Cheers, James NZ

  6. #6
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    Actually I have another question.

    The dash mounted button for raising the suspension for off road driving doesn't work. When I checked the wiring diagram the button shows it acts a a path to earth? So I pulled the button out and swapped it with another one. No joy, so I rigged up another switch with still no joy. I'm guessing at this stage it may be a broken wire?

    So to test this if I use a jumper wire to earth the terminal back at the ecu that should activate the off road extra height? In which case I'll run a new wire to the switch. Does this sound logical?

    Cheers, James NZ

  7. #7
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    Put it in low range and try it again...
    "How long since you've visited The Good Oil?"

    '93 V8 Rossi
    '97 to '07. sold.
    '01 V8 D2
    '06 to 10. written off.
    '03 4.6 V8 HSE D2a with Tornado ECM
    '10 to '21
    '16.5 RRS SDV8
    '21 to Infinity and Beyond!


    1988 Isuzu Bus. V10 15L NA Diesel
    Home is where you park it..

    [IMG][/IMG]

  8. #8
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    Quote Originally Posted by James NZ View Post
    The dash mounted button for raising the suspension for off road driving doesn't work. When I checked the wiring diagram the button shows it acts a a path to earth? So I pulled the button out and swapped it with another one. No joy, so I rigged up another switch with still no joy. I'm guessing at this stage it may be a broken wire?
    Did you check if there is earth on the black wire?
    Discovery Td5 (2000), manual, tuned

  9. #9
    lewy is offline Wizard Silver Subscriber
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    standard setup will do this as well,I have a led fitted to the dash that lights up when the compressor runs.99% of the time when you take off from the lights it will run for a couple of secs.remember they will tend to dump air when stopping as well/
    Darwin
    03 disco 2a td5
    93 tdi disco [gone to a better home]
    2003 d2a v8 retired hurt
    1988 k100rs bmw gone
    85 county izuzu [gone to a better home]
    69 series 2a [gone to a better home]
    series 2a [gunnado]
    series 3 [gunnado]
    and the tinny

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