1985 240 Dies when headlights are on

panamared · Post by **panamared** » 21 Oct 2011, 08:09

The problem started after driving in the rain a couple days ago. While driving it was loosing power, the turn signal even seemed to take it to the brink of stalling. After a few minutes I turned the headlights off and got what seemed like all of the power back. When I stopped the car and turned it off, it wouldn't restart. It started to turn, but it felt like the battery just went. Got it jumped the next day, no rain, and it ran fine for the first mile or so. After that it started to struggle, and almost died, when I turned the headlights off. It seemed to run fine without headlights, but it still seemed to lack enough electrical power, dim turn signal and interior lights. When I got it home, I parked and tried turning on the headlights while the car was running and it died immediatly.
Any thoughts? Alternator? Short somewhere? Battery is four years old.

I know the wiring on the pre-1986 cars are an issue. How hard is it to track down failing wires and replace them?

Thanks

waynej · Post by **waynej** » 21 Oct 2011, 11:40

Put your battery charger on and charge the battery enough to start again. Check voltage across battery with engine at about 2000 RPM. Should read 13.8 to 14.5 volts. Yours will probably read 12 or less. Remove regulator from back of alternator and check brushes. At least one will be worn down to almost nothing. Put in new regulator and your back in business. An easy way to check is to turn on key to run position, if all lights except alternator light come on, that means no connection to brushes. Either bad brushes or the little red wire to regulator is broken of shorted. I hope the jump was done properly or you may be buying a whole new alternator or other parts.

panamared · Post by **panamared** » 21 Oct 2011, 17:42

Thanks for the response waynej, but you'll need to dumb it down for me for it to be any help. First of all, I don't have a battery charger, regulator, or a tachometer. I can get my hands on a charger easily, but will probably have to buy a regulator. Would it make more sense for me to just pull the battery and get it checked at Sears or something? You mentioned the alternator light, thats not a dummy light on my dash, is it? And lastly, I think I jumped it correctly, but maybe not. I hooked up the negative and positive from the jumping car to the negative and positive of my car. Turned on the jumping car, waited a bit, then turned on my car. It took a couple tries, I thought it was just to get the battery charged, but maybe I don't even know how to jump a car. Please explain.
Thanks for your help.

waynej · Post by **waynej** » 21 Oct 2011, 22:13

For a safe jump both keys must be off, connect the positives first then the negatives, then start the good one then the dead one then run both for a few minutes to charge the dead battery. Now turn both off and disconnect negative first then positive.If you make or break a connection and get a spark with key on you can get a lot of damage. Some people get away with it for a while but it's risky. If you don't have and can't afford a battery charger have a friend come over and use jumper cables to connect his battery to yours and run his engine for 10 or 15 minutes. No use running yours during that time since your alternator isn't working.The alternator light is the one with a picture of a battery in the cluster. As far as having the battery tested I stay away from sears, they always say you need a battery and they have very high priced batteries. Have you cleaned the battery terminals? If you have good connections then it is almost certainly the alternator.After the alternator is working and the battery is charged up you could have it tested. It's more accurate to test a charged one than one that's been dead or near dead for a long time.You can purchase a volt meter at most auto parts store for $15, then you can check for resistance at the battery terminals and everywhere between there and the alternator and you can see what voltage the alternator is producing.

panamared · Post by **panamared** » 24 Oct 2011, 14:38

I guess we didn't jump it correctly, got a few light sparks. I removed the battery and charged it with a plug in charger and it charged up pretty quickly. Put it back and the car was starting fine. Funny thing happened when I turned on the headlights, the rear defrost came on automatically. Oil pressure gauge is not working either. Is all the oddball electrical behavior related to a bad alternator, or could it be something else?
How dificult is an alternator replacement? I'll check the previous threads here, but what I did see was a little beyond my abilities.

Thanks

waynej · Post by **waynej** » 24 Oct 2011, 15:00

If the battery was down to where it wouldn't crank and charged up quickly it means it doesn't have much capacity left and you may want to replace it soon.That oddball stuff has nothing to do with the alternator. You may have fried a few things if the key was on when you got sparks. Years ago when I was young and foolish I got a jump on my 740 5 speed.I didn't even see any sparks, but after the jump my cruise control did not work and the up-shift light worked backwards. Did you get a voltmeter and see if the battery is getting charged? If it isn't, did you try just changing the regulator. That's much easier than changing the alternator.

panamared · Post by **panamared** » 03 Nov 2011, 14:10

Finally got a new battery and volt meter, and its running fine for now. No idea about the state of the alternator though. I think the regulator is internal, so replacing it is not quite as easy, or perhaps impossible. My question is, where do I test the voltage off of the alternator? where the battery cable comes in? Also, my battery dash light does not come on, possibly because I have a fuse pulled. The fuse pulled is for the door locks which are shorting and had been draining the battery. Its the same circuit that the dash clock and radio are on. Could that be contributing to the problem? "Bill Of Durham" mentioned some relationship between the dash light and the alternator in a recent thread. One other troubling thing is a hum/buzz coming from the back end of the car, wondering if/how that is related to the electrical situation.
I'd really like to just re-wire the whole car, it runs great otherwise.

Thanks

waynej · Post by **waynej** » 03 Nov 2011, 14:49

To test the alternator have the engine running a little above idle and put the meter leads on the 2 battery post. Be sure to set the meter to DC voltage. It should read something between 13.5 and 14.5 volts. The internal regulator is very easy to change and you don't need to remove the alternator from the car. Two screws hold it onto the back of the alternator. Only 2 things can hum at the back of the car, the fuel pump and the antenna retract motor. The fuel pump should be on whenever the engine is running. If the pump is extra loud the pre-pump may not be working. If the antenna is humming for more than 30 seconds after turning off the engine, unplug it while in the up position. The battery light on the dash light should be on when key is on and engine not running. If not you either worn out brushes on the regulator or a burned out bulb.