alternator only putting out 12volts?

Question

I have a 87 ford crown vic. went out to my car one night and the battery was dead. discovered the next day that the sylinod and alternator were bad and that the previous owners had put the wrong battery in the car. i replace all three defective parts and drove the car home(about 15 miles) no problem. The next afternoon I went to start the car and it was dead. Assuming that the refurbished alternator was bad I took it and the battery up to O'reilly's got both tested and they are fine. Had them recharge my battery went home put both back in and drove the car back up so I could have it tested while in the car. Got it there with no problems and was told the alternator was only running at 12volts and I should replace the wire/plug going into it. Replace those and still 12volts. Took my car back home with my battery at an 80% charge went to go start the car 2 hours later and it is dead!!!

Answer 1

Pyro has a good answer and I will second his motion.

Your description of a 'sylinod' leads me to believe you don't really know what you are doing. You probably meant solenoid, but there are several solenoids all over the car used to actuate electric motors or the starter. Nowadays starter solenoids are attached to the starter. Did you replace the starter as well?

Since you replaced your alternator and battery, one would assume your problem would disappear. This was a good move. Usually when one of the two fails, the other one fails shortly afterwards because they rely on each other for support.

Alternators have connectors and ground wires. I would bet your connections are not secure or are backwards, causing battery drain instead of charge. Check your connections.

Also, verify all the ground straps are secure on your battery. Check all the fuses in your fuse box also. Make sure they all have continuity. You can check this without pulling them. Just place each probe of a DMM in continuity mode on each side of the fuse. If any are discontinuous, replace them.

I am suspecting you have a short somewhere undiscovered.
If all this troubleshooting fails, put a quick disconnect terminal on your positive battery post. Disconnecting after driving the car will prevent the short from draining your battery overnight.
You will need to reconnect every time you start the car.

Answer 2

how can you have a wrong battery? As long as it has enough cranking amps and a its not a lawnmower battery or anything like that ? First i would check the cables to makes sure they are clean and the grounding wires are tight. If you have a battery with side posts, i would convert it over to the traditional top mount, because those side posts are junk. They get corroded and the screw strips. Make sure the belt driving the alternator has enough tension on it. If there is not enough tensions, then the alternator may not be turning over fast enough to generate normal charging voltage. If that doesn't work i would say it sounds like you might have got a bum solenoid. Another possibility is the refurbished alternator too. Generally the alternator should put out 13 or 14 volts when the engine is running. !2 sounds a little low. i have a t bird that puts out 14 or 15. I would swap it in for another unit. Most gasoline cars have a 12 volt system which is what the voltage should be around when the ignition is and the engine not running. When the engine is running it should be 13 or 14 in order to charge the battery and run the electronic accessories. From here i would check all the wires and belt, swap the alternator for good measure ( 12 volts should run the car, but it should be higher than that), and swap out the solenoid. i normally deal with auto zone down in here in GA. They know me and won't try to screw me over.Many of the people at these auto parts stores are not mechanics, so make sure they give you the right part. it always help to take the old part in and make sure the new one matches the old one,

Answer 3

This is more of a matter of competence of whoever told you the running voltage. You most likely have an internal voltage regulator located inside the alternator, so not much more than that could be the problem if it is only putting out 12 volts. The output should be around 14 or so.
Now, it really depends on where the voltage was measured. If 12v was measured at the alternator output post, then the alternator can't be good by any means. however, if it was measured at the battery, you're most likely to have a connection problem in a wire from the alternator. Measure the voltage AT the alternator, and not the battery. Doing so will clear it up more.

Answer 4

An alternator, new or rebuilt, puts out 13.2 to 14 volts normally...you may need to take your alternator back to where you bought it, and get a replacement. It doesn't happen often, but even rebuilt alternators can be bad.

If the second one does exactly the same thing, there may really be a bad wire in there somewhere, even the ignition switch could have a bearing on the problem...

Answer 5

i own a repair shop and you might as well replace the alternator on it,if its only putting out 12 volts that's a little low if you consider it needs to be able to put out enough to charge the battery back and also operate some of the things the car needs to run ,your going to need a battery before too long though,good luck i hope this helps.

Answer 6

The alternator should be putting out about 13.7V minimum to about 14.7V maximum (will vary on different vehicles) to be able to charge the battery. You have got a bad alternator. Thats the easiest way to say it. Replace the alternator and return it for a refund.

Answer 7

It could be simple fix. Blown fuse.

The alternator gets a signal from the ignition switch to "turn on" from the (excite circuit).

If it doesn't get that signal it will never charge the battery.

Check your fuses. Probably a 15 amp in the "Alt" receptical in the fuse box under the dash.

Answer 8

A automobile has a gadget called a voltage regulator that controls while to fee the battery throughout operation. Any automobile charger you should purchase at present additionally has a regulator to stay away from overcharging, in spite of the actuality that some are greater state-of-the-paintings in this than others.

Answer 9

That 12v reading you are getting is the battery itself, the alternator is not charging. Pull it out and take it someplace to bench test it, it most likely needs replacing.

Answer 10

check the battery cables and see if they are corroded, they may not be making a clean connection onto the terminals of the battery.