Need alternator help

[TDIDog]

Just replaced my alternator with a rebuilt Bosch. My old one was overcharging & boiled the battery dry. Replaced it with a rebuilt, now it wont charge. Belt is tight, power to the blue light, bulb comes on with ignition, goes out, when running, but flickers. Checked ground connections. Any ideas would be appreciated. Pulled the alternator out, took it to auto electric shop to have checked, & he says its good.
Thanks
jack

[db_cooper]

Ground strap on the back of the alternator/engine bolt secure and clean connections?

And..take a look at your fuse box under the front boot..be sure the wires there are not burnt or discolored. They do that when they over-charge..drops operating voltage and causes all kinds of problems.

[timmy2]

What year? I'll guess...... '86 from your garage.
Where did the rebuilt alternator come from?
Sounds like a possible failing gauge diode, or a loose connection in the gauge or circuit supplying it. Either will stop it from charging.
Plus what is posted above...

[TDIDog]

Car is an 86, alternator came from a mechanic that has done work for me before. It is a Bosch remanufacture. I know now, I should have gotten my old one fixed, but its gone as a core now. When I took the reman out and to auto electric shop, he tested it on a jig, and it put out 14.5 volts. Thanks for all comments.
jack

[Joe Bob]

You did all the right things.....sounds like an installation issue. Good luck.

[maui44]

You need to take some measurements.

How much voltage does the battery have with engine off (measure at batt)?
What is the reading when the car is running without anything on.
What is the reading when the car is sunning and you have the light on and Fan?

If your car is an 86 it will have an internal voltage regulator which should have been replaced when you bought the new alternator.

[RDM]

Originally Posted by TDIDog

boiled the battery dry.

Unless you've replaced it, I'd be wondering about the battery.

[A horse with no name]

When fully charged with a battery charger it should be 12.7V or up to 13V at normal outside temperatures...If freezing it will be a little lower.

If the charging voltage is less than 13.5 volts when idling, the alternator is not putting out enough current to keep the battery charged. It may even be up to 14.5 but it should not remain that high.

Your car after being started first needs a bit of charging just to get the battery level back up and of course when driving voltage is often being consumed by a few things such as the ignition, radio, heater ect.

When your car is idling with the lights and fan on ect - it should be at least 13.5V - 14.5V. Anything over that for any length of time would indicate that your voltage regulator in the alternator is gone. If your battery and alternator are both in good condition the recharge time is not that long...Possibly a mile of driving.

Keep in mind that in the winter time most often the lights, heater, windshield wiper, rear defroster, mirrors defrosters ect will more often that not be on -The exception being the South West & Florida of course.

In these conditions if the car is only being used for short trips, such as a 1/2 mile with the above items being on, you will in time need to put it on a battery charger. The reason being is that you are not driving it far enough for the alternator to pick it back up to where it should be.

Cheers

Originally Posted by maui44

You need to take some measurements.

How much voltage does the battery have with engine off (measure at batt)?
What is the reading when the car is running without anything on.
What is the reading when the car is sunning and you have the light on and Fan?

If your car is an 86 it will have an internal voltage regulator which should have been replaced when you bought the new alternator.

[kodioneill]

Originally Posted by RDM

Unless you've replaced it, I'd be wondering about the battery.

Agreed; you need to replace the battery if it was boiled dry.

[TDIDog]

Thanks guys, the battery was new, and fully charged when I put the reman alternator in. When I checked the voltage of the battery, it had just come off the charger, so may be higher than what the alternator is putting. I will try running car again, and turn lights, fan etc on and take some voltage readings. Thanks again for all input.
Cheers
jack

[jim tulloch]

ground could be a possibility..but...i think it is caused by the alternator.i have seen this before. maybe someone could loan you an alternator to check...i know, it's a pain

[maui44]

Nice little meter because you can monitor things while your driving.

Amazon.com: Prime Products 12-2020 12 Volt Digital Meter: Automotive

[TDIDog]

I checked the voltage today. 12.5 without the engine running, 12. with engine running, rev up to 2000rpm, still the same. Gen light comes on before start, goes out once running. Flickers at idle. Looked in fuse box for burned wires, but could see any. Car worked fine before alternator started to overcharger, so don't know why there would be any other problem than the voltage regulator. Any more ideas welcome. I will try to get another alternator. Thanks
jack

[K Sykes]

I was having a similar problem. Cleaned up all the grounds, made it a bit better ~ .5 volts. Added a new + wire from the alternator to the starter, now it charges 13.5 - 14+ volts. One more thing to check.

[James Brown]

if it is 12 with the engine running, it's not charging. double check where the wires are on the alt. and make sure all the wires are good that go back to the battery. if you remove the battery ground wire with the engine running and the car dies, the alt is not powering the car.

[maui44]

+James Brown - Right now, you do not have a working alternator. Double check that all the wiring is correctly and well connected including ground strap at each terminal.I would use a multimeter and ensure I have continuity from end to end on each conductor. If you do, I would replace the Bosch alternator. It should be under warranty.

[mgro1959]

HI Jack: As previous two Pelicans said if you are showing only 12 when it is running then you are drawing from battery and alternater is not working. I spent 7 hours working on a TR6 that would start but die. I had replaced a condenser and points a month earlier and the guy drove the car twice. Who would have thought to check a brand new installed part. Found all sorts of problems but in the end it was a virtually brand new condenser that had failed. Waiting for the brand new one to fail next week. Your new aternator may have a faulty internal regulater or one of the diodes may have failed. Thanks Rob

[Joe Bob]

He says in his opening post that he had it checked. He could pull it, swap in another and/or check it again.....it's either THAT or there is a install problem with a bad connection, most likely to ground.

[autobonrun]

Originally Posted by Joe Bob

He says in his opening post that he had it checked. He could pull it, swap in another and/or check it again.....it's either THAT or there is a install problem with a bad connection, most likely to ground.

I think you are on the right track. Assuming that the electric shop checked it well and diagnosed it correctly can send you down the wrong track from the start.

I had an alternator light come on several years ago. I took it into an electric shop and a diode was determined to be bad and replaced. This part he got right. I put it back in and it ran maybe 30 minutes before the light came back on. I pulled the alternator again. Long story short I would repull your alternator and check these items:

1) commutator brush sticking in holder causes intermittent contact
2) a broken push down spring behind the brush allows intermittent contact with the commutator and a flickering alt light
3) old/cracked solder at the diode joint will cause a flickering light from the intermittent contact

I'm not sure if the electric shop did anything other than confirm charging and continuity. I had each of the issues described above. In item 3 above, my alt light kept flickering. When I pulled on the wire to the diode, the old solder completely came out. When it was in place and visually inspected you could not even tell it wasn't fine. I'd remove all the 30+ year old solder and resolder the wires at the diode. It doesn't take long.

Most of these issues occured during one repair attempt. It took me 3 hours to pull the alternator the first time and 40 minutes the last one.

[TDIDog]

I did check for continuity to the ground. Didn't want to loosen the bolt on the engine to check that connection, as I don't know if that is supposed to be torqued. I put the battery in to check voltage at engine, before I installed alt, and I had 12.5 volts. Blue had power once key is turned on. Don't know why the alt light goes (but flickers) out once running though. Seams to me that any car needs to have the battery connected to run, even if alt is charging, but I could be wrong. The wires are pretty hard to mix up, as the only fit on one terminal.I think I'm going to take alternator back to where it came from and get him to get me another. I'm getting a lot quicker at doing the install too, but it's not something I want to continue doing. Thanks again for all the tips
I wish I had my old one back, & I'd just get it fixed!!!!