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Life span of ECU? 900 1994

posted by  U.S. Diver on  Thu Dec 20 10:10 CST 2018
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I am a believer in preventative maintenance, of replacing things before they fail, especially those that can leave you at the side of the road.

I realize this is not always possible.

In this spirit, though, does it make sense to replace the ECU at a certain point rather than wait for the day it fails? How about other electronic parts that will fail?

Or is this a case where the lifespan has no rhyme or reason, and the replacement may be more a detriment to reliability than the original?

In other words, if not broke, don't fix?

Your thoughts appreciated. Thanks.








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    Life span of ECU? 900 1994

    uid 27's pic
    posted by  Art Benstein on  Thu Dec 20 11:56 CST 2018
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    last visit: Fri Oct 17 20:10 CST 2014
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    Yes, replace it now.

    Not because it might fail due to age or use, which is unlikely, but because there's a better chance you'll run into a problem one day where the ECU is among the suspects. So if you've replaced it with an easy-to-find-when-not-under-pressure used part, tested it, and stored it or its working original, you'll have a known-good unit to swap in. ECU problems are rare enough as to be difficult to diagnose without a spare to substitute. Price of keeping an old car with an old computer.
    --
    Art Benstein near Baltimore

    “The single biggest problem in communication is the illusion that it has taken place.” George Bernard Shaw








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      Life span of ECU? 900 1994

      posted by  Chris Mullet on  Thu Dec 20 12:32 CST 2018
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      last visit: Fri Oct 24 09:08 CST 2014
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      "...So if you've replaced it with an easy-to-find-when-not-under-pressure used part, tested it, and stored it or its working original, you'll have a known-good unit to swap in...."

      Will one of Dave's spares work? (The price is right.)

      https://www.brickboard.com/CLASSADS/index.htm?id=17324
      --
      Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)








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      Life span of ECU? 900 1994

      posted by  U.S. Diver on  Thu Dec 20 12:04 CST 2018
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      Thanks. I believe mine is the LH 2.4. Is there any particular source you prefer for obtaining ECU's? Are they difficult to remove and install?

      Thanks.








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        Life span of ECU? 900 1994

        posted by  spook on  Thu Dec 20 14:46 CST 2018
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        Dear U.S. Diver,

        Hope you're well. I bought spare ECUs a decade or more ago, and have stored them in a dry, cool place. Thus, I can't help with sourcing.

        As to removal/installation, that's not hard. The ECU's home is behind the door-side plastic panel in the passenger's footwell. Before an ECU swap, be sure to disconnect the negative battery cable clamp from the negative battery terminal. Put the end of the battery cable into a plastic bag, to isolate it.

        If memory serves, it's necessary to remove the threshhold strip's front screws (under the rectangular plastic micro-panels). This allows the tip of the footwell panel to be taken free. Go gently: old plastic is brittle.

        The wiring connector is thick and will be stiff, having not been disturbed for at least 20 years. Thus, move it gently. The ECU sits in a metal holder, secured by T-20 screws, if I recall correctly.

        Hope this helps.

        Happy Holidays!

        Yours faithfully,

        Spook










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          Life span of ECU? 900 1994

          posted by  U.S. Diver on  Thu Dec 20 15:47 CST 2018
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          Thanks, Spook. Do I have to match the serial number of the existing one? Must I pull it out to ascertain that number?

          Happy Holidays!








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            Life span of ECU? 900 1994

            posted by  spook on  Thu Dec 20 17:26 CST 2018
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            last visit: Fri Oct 24 08:06 CST 2014
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            Dear U.S. Diver,

            Hope you're well. The part number - Volvo, Bosch, or Bendix - should match exactly.

            Thus, if you have Bosch ignition and fuel management, and the ECU's Bosch part number 0 280 000 946, be sure to replace that ECU with a unit bearing that number. I don't know if, for example, an ECU with part # 0 280 000 943 would also work.

            Hope this helps.

            Happy Holidays!

            Yours faithfully,

            Spook








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            Matching ECU serial numbers 900 1994

            posted by  Amarin on  Thu Dec 20 17:22 CST 2018
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            last visit: Thu Oct 23 22:42 CST 2014
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            "Do I have to match the serial number of the existing one? Must I pull it out to ascertain that number?"

            Yes in most cases but you could refer to the page below for alternative ECUs:
            http://www.nuceng.ca/bill/volvo/database/ecu.htm

            IME our 940 LH2.4 ECU are long life items. Their electrolytic capacitors inside may eventually dry out but you could replace them, say every 15 to 20 years. These are available at online parts store like Farnell and Maplins. Replace those capacitors with ones having similar ESR (electrical series resistance) for proper operation of voltage regulators inside the ECU. For this you'd need to refer to the old capacitor's datasheet and choose similar ESR when ordering the new ones. Lastly our ECUs internal solder points don't subject much to cracking so reflowing is rarely needed.

            Get a spare ECU at eBay. They typically cost around 80-150USD.


            May these help,
            Amarin.








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    Life span of ECU? 900 1994

    posted by  Chris Mullet on  Thu Dec 20 11:06 CST 2018
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    last visit: Fri Oct 24 09:08 CST 2014
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    "...In other words, if not broke, don't fix?..."

    That approach would get my vote, especially if your car has a Regina fuel control system with the Bendix ECU. That ECU will likely still be working when the rest of the car has crumbled to the ground.
    --
    Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)







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