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Old 02-10-2015, 02:39 PM
v8volvo v8volvo is offline
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Join Date: Jun 2009
Location: Montana, USA
Vehicle: '86 745, '83 764
Posts: 1,618
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What does the battery light on the dashboard do? Any other strange behavior?

If the bulb is blown or there is a problem with the instrument cluster circuitboard or elsewhere in the D+ (exciter) circuit upstream or downstream of the cluster, you'll have a no-charge issue that sounds like what could be happening. If you never see the light come on at all, even with key-on/engine-off, then you'll want to disconnect the wire from the D+ terminal on the back of the alt and ground it, and see if the light comes on. If it does, then the problem is in the alternator. If it doesn't, then you have either a bulb or a wiring problem. Engine wiring harness is suspect on early '80s cars so you could start by checking for continuity in that circuit from the big rectangular 8-pin harness connector on the firewall to the wire at the alternator. If there's continuity there, then you will want to check the bulb in the cluster and troubleshoot the rest of the circuit to see where there's an open. Power needs to flow through the warning light bulb's filament and onward to D+ on the alt, so anything interrupting that will cause the alt to not charge. (Including driving the car repeatedly with the cluster out!)
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86 745 D24T/ZF 345k lifted 2.5"
83 764 D24T/M46 155k
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