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Mystery Battery Drain 700 1989

posted by  BobbyC on  Wed May 23 10:21 CST 2012
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last visit: Tue Oct 29 08:31 CST 2013
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I've had an '89 740 for years, and I have ALWAYS had to disconnect the battery if not using the car every day because the battery goes dead from a paracitic drain of about 1 amp.

I have isolated a relay that is staying energized with the ignition off. When the battery is disconnected, the relay releases (I can hear and feel it click), and does not re-energize when the battery is reconnected (and the battery drain is then zero).

Something is providing enough current to hold the relay closed as long as the battery is connected, yet once the battery is disconnected, simply re-connecting the battery will not cause the relay to close until the ignition is turned on or the started is engaged.

The relay is a 4-Pin unit (round pins) and is clipped to the metal bracket on the coolant expansion tank. With the relay disconnected from its harness connector, the engine will crank, but not start, and if disconnected while the engine is running, the engine shuts down.

The relay has a Volvo Part# 898831 1323592-1 and is marked "12V/40A"
It's listed as a radio suppression relay (or fan relay if an electric fan is fitted) at "Dave Barton Relays", but the wire colors don't exactly match the suppression relay ("264") in the circuit diagram.

I cannot locate the relay on a "LH-Jetronic 2.4, B234F, B204E" wiring diagram, or on a component location diagram at http://www.autoelectric.ru/auto/volvo/740/1989/740-89.htm
UNLESS it IS the radio suppression relay.

The problem is complicated in that the car has a Clifford "III" security system that may be contributing to the problem. I have no idea how the system is wired, or what it interferes with or if it is connected to the relay in question. My cousin had it installed when she bout the car new ($500 if you believe that!), but has no idea how it works now. The installation manual mentions a ignition/starter disable relay, but I've found no such relay, either, though thankfully w/ the power wire (red) removed from the fuse panel (it was connected using an add-on terminal) the siren no longer blows when the battery is connected, and the car still starts/runs.

The relay has the following color wired connected to it:
Red, Green w/ Red, Black, and Yellow w/ Black

Any hints or a link to a wiring diagram would prevent this stupid nightly battery disconnect process.

If it IS the radio suppression relay, and it is energized by the Fuel Injection Relay (135 shown with a blue arrow), it should ONLY be energized when the Fuel Injection Relay is energized, and should drop out when that relay opens. See diagram: http://screencast.com/t/9qMrQvXU









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    Mystery Battery Drain 700 1989

    posted by  aleekat on  Wed May 23 11:33 CST 2012
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    last visit: Fri Oct 24 13:19 CST 2014
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    First forget about the color coding wiring. Volvo has some switching done over the yrs. Rockauto does show that part number as the radio suppression relay. And from what you describe disconnecting it, prevents the injectors from opening. I would clean on the relay contacts and the connector and track the ground and make sure you have a good ground. Many have re-flowed the solder on both the radio relay and fuel pump relay. Not sure but I believe that relay as a constant 12v going to it, and when you crank the ground is closed completely the circuit. Maybe the contacts are burnt a little and won't allow the contact to open once you shut the car off unless you remove the 12v source(battery)
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    Post Back. That's whats makes this forum work.








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      Mystery Battery Drain 700 1989

      posted by  Klatu on  Wed May 23 20:01 CST 2012
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      last visit: Fri Oct 17 21:22 CST 2014
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      My 91 740 did the same thing. Except I dont have all the security stuff. After 2or 3 days the battery would be dead. If you can, look under the intake mainifold. Just behind the altinator. See if there is a ground wire connected above the idle control valve. Mine was loose. It's just like new again. It doesn't matter if it's running or not. That wire does must do alot. It might also need cleaning at contact point.








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        Mystery Battery Drain 700 1989

        posted by  BobbyC on  Wed May 23 20:13 CST 2012
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        last visit: Tue Oct 29 08:31 CST 2013
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        I will examine that wire mentioned tomorrow-Thanks.

        If the engine is off, I don't think the injectors are supplied with +12v on the other side, since the injection relay would be open (I'll confirm this tomorrow).

        If that's the case, I can't see why leaving the ground side of the injectors grounded would hurt anything. The radio suppression relay UNgrounds the injectors when it opens, but if the other side of the injectors isn't energized, I don't see why grounding the other side 24/7 would change, or hurt anything.

        In other words, if I cannot cause the relay to release (as I cannot now), the relay is grounding the injectors 24/7 NOW anyway, and nothing bad has happened other than the relay coil discharging my battery slowly).

        So if I were to remove the relay, and jumper the injectors to ground, electrically I would have the same condition I now have (grounded injectors), but the drain from the coil would be gone (since the relay would be gone), and my battery would not go dead.

        Make semse?

        Bob








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          Mystery Battery Drain 700 1989

          posted by  Klatu on  Thu May 24 02:52 CST 2012
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          last visit: Fri Oct 17 21:22 CST 2014
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          I couldn't figure out how a loose ground could cause a power drain either. Sometimes on this car (its a good ole car) I start hearing Twilight Zone Music.







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