I have a POS 90's ford that has a bad alternator. I have heard that when your alternator is bad it will drain your battery. That is the issue I have. Before the alternator would work but would drain the battery, now the alternator does not work and still the battery drains. So what would cause this in the alternator? I assume the brushes are good because the battery draining was before and after it failed. Or maybe just buy a used alternator? I would rather just repair it myself for ease of mind that I know everything inside of it is perfect and will not fail again, and not buy a new one for more then the car is actually worth.
Car alternator repair
- Thread starter silviasol
- Start date
Hillhater
100 TW
If you think you can fix it, .....then you should be able to fault find it first !
...Me, ...i would just get a replacement from a wreckers yard for $20 or so !
...Me, ...i would just get a replacement from a wreckers yard for $20 or so !
marty
10 MW
Test don't guess. Charge battery all night. Remove charger. Let battery settle down for 10 minutes. Measure voltage at battery. Start car and measure voltage at battery. Write down the two voltage readings. Post em here.
marty said:
I will buy a new battery and post the results. I haven't driven it for years. When I did drive it just on battery only on short trips the battery would die after 3 or 4 months and I would always unhook the negative terminal after driving and bring it to a full charge.
I bought a used battery. It has been sitting at the same voltage for over a day now. Turns over just as strong as after I first fully charged it.
Could the problem have been me draining the battery, then charging it every day? Are they suppose to stay at the full 12v in order to stay healthy?
Could the problem have been me draining the battery, then charging it every day? Are they suppose to stay at the full 12v in order to stay healthy?
Punx0r said:
Makes sense. Funny I didn't know anything about batteries when I used to drive it and never thought of that. I am going to skip replacing the alternator and just use my 6s 20ah pack with a step down converter to hold it at 12v so it doesn't get damaged.
Hillhater
100 TW
avoiding fixing the problem, but spending cash on issues caused by the original problem ?....not the best idea ! 
Hillhater said:avoiding fixing the problem, but spending cash on issues caused by the original problem ?....not the best idea !
The converter was $6. I have an amp meter I can hook up to it to monitor voltage and amp. I already have the 6s pack built and in a case to easily bring along in the car. This car also has a bad gasket and oil leaks on the engine, blows white smoke, rusted, paint chipping off..... it is not worth even spending an hour of time on it.
Also the alternator is not in an easy place to get at in this car. I only need it to keep warm when I need to go to the store or drop off my mail this winter, instead of riding my bike. Next summer I will take time to find a good deal on one of the few model cars that I want.Ok one week later and the battery is dead. Luckily it charged back up, hope that didn't kill it. I talked with the mechanic I bought the battery from and he says there is some diode or something that is known to drain the battery on this model car. Going to have him look at it and replace the alternator and diode.
The diodes are in the rectifier which is part of the alternator. There are only four things that go wrong with alternators: 1) diode failure = reduced output and discharges battery 2) worn or stuck brushes = doesn't charge 3) failed regulator = over-charges 4) bearing failure = whines, squeals, shoots sparks
marty
10 MW
silviasol said:
marty said:
marty said:
I did that. It was 12.87v then let sit overnight and was hardly any less, I think it was 12.83 or something. So then figured it was just the fact I would drain the battery while driving that killed them. I will try again, right now it is 12.97 after sitting from a full charge and will check tomorrow.
marty
10 MW
Are those voltage readings with the car off? If yes? Start the car and measure while it is idling. Those two numbers car off, and car idling will tell a lot about how the charging system is doing.
Anything about 12.65V is surface charge which will dissipate naturally within about 24hrs all by itself.
If the battery has been on the car between this time when clearly the alternator is not draining the battery, it's just failing to charge it while the car is running.
My personally favoured solution would have been to spend $20 on a used, working alty two years ago and save a ton of hassle having to keep charging the battery and buying replacement batteries...
If the battery has been on the car between this time when clearly the alternator is not draining the battery, it's just failing to charge it while the car is running.
My personally favoured solution would have been to spend $20 on a used, working alty two years ago and save a ton of hassle having to keep charging the battery and buying replacement batteries...
