1986 Volvo 240 GL Battery or Alternator?

Hi,
I have an 1986 Volvo 240 GL and the Alternator warning light started to appear a few days ago. I bought a replacement alternator this morning and replaced it with the old one, drove the car around for a half hour and not only did the alternator warning light not go out but the vehicle seemed to be completely drained of power. The headlights were dim to the point of being dangerously un-illuminated as were the interior dash lights. I am tempted to just go out to buy a new battery now but does this sound like a battery issue or something else to do with the charging of the battery (re: I screwed up the alternator installation)?
Thanks alot for your advice.
Matt. most of the time that lite being on means a problem with the alternator or the wiring connected to it. it sounds like the car is running off of the battery, and its getting low cause the alternator aint charging it. if u dont charge it up soon itll die completely and the car wont run.

theres a few things here u can check. first, go back over your work and make sure all the wires are connected where there suppose to be, and that the connections are clean and tight.

next, follow the 'hot' wire from the alternator to the other end, probbly the starter motor. see if theres a fusible link there. itll look something like this:



check the link for signs of burning or melting. if it looks ok, pull gently on it. if it stretches out like a rubber band, its burned out and needs to be replaced.

another possibility is that the new alternator is bad. youd be surprized how often this happens, when we see a new part thats doa right out of the box. one way u can check it is with a dvom set to volts. with the engine idling and all electric stuff off, touch one lead to the battery post and the other lead to the battery - post. u should see around 14 volts or so. if not, move the lead from the battery post to the hot wire connector on the back of the alternator. if u get 14 volts now, theres a problem in the wiring somewhere. if u still dont get 14 volts, its a sign that the alternator is bad.

if all the wiring looks good, and evrything is hooked up right, but the alternator aint putting out around 14 volts, take it back where u got it and have them check it, and exchange it if its bad. Thanks so much. I will take a look and post when I have got the problem fixed. again, cheers.