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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