When the car is running the battery light on the dash is off, but as soon as I turn the car off, the light comes on. This first happened after I finished fumbling around with the electrical connections that are just behind the steering wheel because I figured cleaning them with rubbing alcohol would fix the problem with my wipers not working, however it did not.

But now my car won't start unless I charge the battery overnight. Also, I don't know if this is relevant to the problem or not, but the belts on my car were recently replaced by a mechanic and now I hear a screeching noise that only occurs for around the first 5 minutes of driving.

Any help would be greatly appreciated, thanks in advance.

Derek

 

Most likely the alternator diodes are faulty.


Cheers
DD

 

The Lucas alternators had "thick film" technology to provide the control and the diodes are part of that, I think. Of course you may have another make of alternator.

 

Would this mean I need a new alternator? Also, do you have any idea what the screeching noise is?

 

The alterantor needs repair or replacing. many twon have a local "starter and alternator" reapir shop. If not you'll have to order a rebuilt unit.

If you plan on removing the alternator yourself post back for some tips

Screeching is almost certainly a loose belt. They often stretch a bit after being replaced and then need to be re-tightened.

Cheers
DD

 

Hold up--

Car running = Batt lights OFF = normal.
Car NOT running = Batt lights on = normal.

Or am I missing something?

Screeching = loose belts (generally), = not charging = dead Batt = requiring overnight charging.

As Doug says, I would suggest checking belt tensions before even going any further. (costs nothing).

Depending on what you find, and post, Doug and Fraser may educate me further as always (thanks guys)

 

I took it to mean that with the engine not running and the key "off", the battery light comes on and stays on.

Maybe I misunderstood?

If the engine isn't running but the key is "on', then yes, the battery light will come on.

Cheers
DD

 

No Doug, I think it was me that misunderstood. If the key is off and the batt light comes on, then I'm with you.

Not a fix by any means, but maybe disconnect the battery every time you shut down (will cause headaches and further electronic problems over time).

 

I'll probably just replace the alternator myself if I'm able to. Autozone said one for my car would be around $150. I haven't asked around to find if that's the best price, but I will.
and I'll get back to you about the screeching after I tighten the belts.


No, you didn't misunderstand. When the key is off, and the engine is NOT running, the battery light is on for some reason.


This is what I've been doing, I turn the car off and disconnect the positive battery cable and reconnect it whenever I'm ready to go somewhere else.

This causes further electronic problems?


Thanks for all the help guys!

 

^ over time. The computers are not going to appreciate being disconnected/reconnected frequently, and they won't like the spikes that failing diodes can allow.

I'd get your alternator checked if you can.

Right at the beginning you mentioned you had the belt changed, but didn't say if this was just routine maintenance, or an attempt to cure a charging problem.

If it was the latter, you did the right thing, but did not cure the problem, so next step, test alternator and I'll bet that Doug and Fraser were on the money.

 

Yeah, I'm planning on replacing it as soon as I get the money. As for the belts being replaced, I had them all replaced simply because there was a loud screeching noise that I assumed was coming from the belts. However, the screeching is still there. I still haven't gotten the opportunity to give tightening the belts a try yet. When I do I'll post an update.

 

I am adding to this thread since my base problem is similar to the original poster's.

While driving to work last Friday everything was fine, not idiot lights. When I turned the car off, the battery light came on and remained on. It remained on after I removed the key from the ignition. I disconnected the small wire going to the alternator so that the battery light wouldn't stay on the whole time I was in the office. I did not have any tools to disconnect the battery at the time. When I came out (~8 hours later) she fired up, and I drove home (~35 mins of back road driving, some stop and go). When I got home I put my multimeter on it and tried to check a few things. With the engine running I am seeing 13.3V at the battery terminals. With the engine off, I am seeing 11.87V. I then disconnected the battery terminals to isolate the battery and saw right at 12.0V.

Oh, and I just replaced the alternator ~5k miles ago.

I know this isn't much to go by, but do you think I have a short somewhere, alternator failure, simply a dying battery (it's ~4 years old), or something else?

I am a mechanical engineer so electrical things are not my forte, feel free to let me know if I have done something wrong or give me basic instruction on any other tests I can run.

I wanted to add that I reconnected everything, including the small wire to the alternator and all the same situations exist. Battery light on when engine off, I restarted the car and the battery light went out and same voltage readings.

I am leaning towards/hopeing it is a dying battery. As one final test I have put my battery charger on it (at 12V 6A),and I wanted to see if the light went out. Any idea if this seems like a realistic test? If so, at what voltage is that light designed to come on and off at? I'm currently charging and the readings are going at 12.25 and climbing. It seems to have peaked at 12,45V and the idiot light is still on. When I disconnect the charger, the voltage readings immediately start dropping and heading towards the 11.87V reading from before.

I have found a YouTube video that says I can load check using my multimeter (Fluke 87 III) so I'll try that next.

Well, I'm not sure. The guy prefaces his test by saying the battery should be at 12.6V for meaningful data. I'm not at 12.6V. I went ahead anyway and ran the test which is nothing more than a constant reading of the volts during cranking of the engine and then I can see min and max. He said if the min is less than 9.6 than the battery has failed. My min was 9.88V. I will trying charging again and rerun the test one more time.

Thanks,

Eric

 

Having a Fluke VOM is "high on the hog". Quality.


Add to it's usefulness. make a patch cord for the cigar lighter to VOM. Now, you can check voltage under various load and RPM's. Very useful. I exonerated an alternator and convicted a battery that way.


I almost did not mention it. Rock auto's service is great. I got a nice pair of reconditioned rear calipers there for a good price and no messing with cores. So far so good.


But, my experience with starters was/is ??? But, too their credit, they honored the warranty promptly.


Time for a Delco to replace an ancient Lucas? Johnscars offers a kit, instructions and even an appropriate alternator. Not that there is anything wrong with a properly rebuilt Lucas. And, Autozone is a responsible firm.


Carl.

 

I would personally never buy anything electrically from Autozone. They outsourse the CHEAPEST and never quality. In the past I have had to return(the do great swapping out bad crap) way to many things. Told myself years ago "don't even bother". My 2 cents. When it comes to rebuilt stuff from anywhere, It's always a risk. From my past experiences autozone was the worst. I used to like NAPA, but they changed there policy's for warranty's to you have to take it to the store you got it from or your screwed. That doesn't work when you travel alot.

 

Thanks Carl,


I found the Fluke used. It is a nice piece of equipment. Much more capable than I am. Can you give me some more details on how you determined the alternator was ok and the battery was guilty? I'd like to better understand how to use my multimeter.


Thanks again,

Eric

 

Only sorta. I just barely get along with the electrics. But, here we go.


1. Plug in the patch cord. Turn on the key. do not start the engine. This receptacle is only alive with the key on. You are now reading true volts in the system. May or may not be different than volts at the battery. That connector thing.


2. Start the engine. Let it idle. Note volts. Greater than those seen in 1.? Yes, alternator working, good. Same, might be not so good.


3. Rev up to about 1000, or 1500. volts oughta be up a bit. No, alternator not working at all.


4. Revs still up. Add loads. AC, lights radio, rear window heater etc. Same as in number one or slightly greater. If yes, alternator capable, if no, it isn't. Bummer.


5. Let battery lay fallow. Measure volts. Holds volts, mebbe OK. Loses them, not good. Short/drain in the battery or in the car wiring. ,




Mess with it and think.


Carl


l

 

Can someone post a picture on how to connect to the cig lighter please?

 

I wanted to close this out and let everyone know that my issue was the regulator in the alternator was going bad. Replaced alternator and all is good again. I just wish the damn alternator were easier to replace...

 

Patch cord manufacture.


There are various devices that plug into a cigar lighter for power. With the no smoking thing, they are now more likely to be known as power outlets.


Shavers and cell phone chargers use them. The electrics display at CARQUEST and the like probably have them. I think mine came from a defunct "jump" box.


A visit to Radio shack, meter in hand will likely come up with probes for the out cord. Possibly with a cord attached. Black for ground and red for + is handy.


Now, mate the two. Use your continuity feature on the meter to match + to + and - to -.


Very handy addition the VOM!!!


Carl

 

Oh, Radio shack may have the plug for the lighter as well. One trip insteasd of two.


But, deprives one of two pleasures.


1. looky look in a candy store.


2. Drive the Jaguar.




Carl