Hello everyone! Just recently purchased a 240 Wagon and have been loving it, however it just recently died on me. Jumpstarts and starts right up so figured it was the battery/alternator route. I tested the battery and the battery was bad. Threw a new one in and it starts up right away too. However, I noticed that even in the second position my battery light never comes up on the dash. Switched bulbs with one that was operable and no light. I am beginning to think there is an issue with the small red wire on my alternator that is the battery light switch or something like that. If I can get the light to work, I can maybe see if that completes the circuit, and I can then see if the alternator is the issue before having to pull it and test it. Attached is a photo of the connector. Any ideas on how to test or get this light operable? Thanks!

 

That small red wire wire goes directly to the bulb in the dash. (through a couple of multi-connectors) If that wire is grounded the alternator light stays on. So unplug the small red wire and using a jumper wire ground it to the engine/chassis/body. If the wiring connections and bulb are ok - the alternator warning light will be on (with the key in the second position)

If the light is not on - that red wire snakes under the intake manifold and is in the 8 pin grey multi-connector on the firewall near the back of the valve cover. The harnesses shred there. Try grounding the wire there. If those wires are shredded - try not to touch them - that will only make things worse. Or use your ohmmeter to check continuity from the instrument cluster to the alternator. Many times a new wire gets run from the firewall to the alternator to solve if the wire is open in the harness. Just run the new wire along the firewall and down the right fender coming across to the alternator from the right (washer and coolant bottle area. )

But before you do any of that - the alternator is mounted in rubber bushings - so there is a ground strap from the alternator to the engine block. Make sure it's there (that certainly looks like an aftermarket alternator) You could also simply use your jumper wire to ground the alternator case to the engine block to check if the ground wire is the problem.

Purchase a $7 cheap volt-ohmmeter, a cheap 12v test light and a jumper wire with alligator clips on it each end. You will be able to test your alternator, test for open circuits yourself. (without taking it off and taking to the local autozone, etc) And those tools will come in handy for many other repairs on that old Volvo.