RED LIGHT = LOW BATTERY CHARGE???

[mgbnew]

First of all thanks again to all those who assisted in trying to determine the RED LIGHT mystery. ( don’t you all just love us new owners.). And especially to Keoke, Sultanoswing and to Bruce. They all go to the top of the class. I had my son help me push start the Bee and took it to Peninsula Imports in Oakville.(that will mean nothing to most of you). I told the mechanic the problem with starting and had all your suggestions printed out so as to show him what other “experts” thought could be the problem. I called the next day to see if the car was ready and the mechanic said that they are still trying to figure it out. Alternator and starter seem OK He called today and said that after checking everything over they decided to give the battery a charge. This seemed to eliminate the problem. The car started every time they tried it. The left it overnight and tried it this morning and she started right up. I remember when I purchased the car that the owner said that he had replaced the faulty battery with a cheap Canadian Tire battery. Anyway she is up and running and the weekend weather forecast calls for three days straight of /ubbthreads/images/graemlins/laugh.gifMGB weather. I guess my question now is do I go and buy a better battery? And also does this diagnosis sound reputable or am I going to run into problems starting her again?

 

[Keoke]

Well MGBNEW, that sounds plausible. However, if you have a battery charger you might just give it a shot overnight,or take it to another shop and ask them to load test it for you.Nice to be sure about things like that. But generally cheap batteries can cause big headaches.---Keoke /ubbthreads/images/graemlins/laugh.gif

 

[Dave Russell]

Apparently, on an MGB, a red light can indicate a low alternator output (alternator voltage lower than battery voltage) OR a low battery (battery voltage lower than alternator voltage)

Check out this reference:
https://www.mgbexperience.com/service/understand-alternators.php
Very strange way to do it, if true, or so it seems to me. Sort of like an ammeter that goes only in one direction no matter if the battery is charging or discharging. The light only goes completely out if the battery is fully charged & it's voltage matches the alternator voltage.
D

 

[sultanoswing]

Simple check now - bang a voltmeter over the battery terminals...on a fully charged battery, with the engine running at a couple of thousand revs, you should be getting AT LEAST 13 volts, preferably 13.5 or so. Fire up the heater, wipers, lights, and turn signals....still got more than 13 volts?

If not, you may be the victim of a dying alternator or inadequate charge. Ultimately your experience will include another dead battery, non starting and even ceasing to spark at all!

Your battery will probably be fine, unless it gets really cold (what is the CCA rating?). At least it SHOULD now be ruled out as a source of problems...fow now (cheapo batteries tend not to last as long).

SoS

 

[Bruce74B]

The old DIEHARD battery in my B goes dead if she sits for more than a couple of weeks without running, so I bought a little trickle charger that plugs into the wall and gets clamped to the battery for extended storage. It works so well that I think I will hook up a quick disconnect wires for it so I don't need to remove the rear speakers, carpet and battery cover everytime I hook it up.

I did buy a cheap battery for in another car that my boys use when the Jeeps are not running (fairly often) and it died in six months. Of course, we lost the reciept and paperwork, so I stuck an old battery back in for the summer. I will go get a DIEHARD for it this winter though, before son #2 takes it to college with him. Looks like my spare will be an old Jeep Cherokee this year /ubbthreads/images/graemlins/crazyeyes.gif

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[Bugeye58]

I've been driving the '72 Midget for three or four years with the alternator light on. I checked, and its putting out around 14 volts, so I just ignore it. It's only the lamp circuit that's bad in the alternator, and one of these days I'll get around to addressing it. /ubbthreads/images/graemlins/hammer.gif
Jeff

 

[piman]

Hello all,
although not necessarily related to poor starting, the ignition warning light will also be on in the case of overcharging; usually getting brighter if the engine is revved. This does the battery no good whatsoever.

Alec

 

[mgbnew]

Thanks again to all. I hope not to see that red light again for a while. Now it's onto replacing the top.

<font color="red">Al
1970 MGB</font>/ubbthreads/images/graemlins/cheers.gif /ubbthreads/images/graemlins/canpatriot.GIF

 

[Kryllion]

I'm grave-robbing old posts...

My light comes on when I'm idling for the first few stops coming out of the house. After the car's been running for a few minutes, it stops being a problem. I suppose that means that my battery and alternator start matching after a while.

Should I be concerned?

 

[Steve_S]

It's fairly normal for the ignition lamp to glow when at idle, especially on early cars with generators. The lamp should be out completely by the time you hit high idle or above though.

 

[Kryllion]

Right on... thanks /ubbthreads/images/graemlins/smile.gif

 

[Bob Claffie]

There are two different cut-in / cut-out points on the generator cars. On my former '72 B the red light would stay on until I hit approx 2800 RPM but would stay out until revs dropped to around 1000. With the radio, highbeams, heater all on the light would glow slightly and often the battery would be close to dead after an extended trip as I would be taking more elec out then putting in! Bob

 

[Steve_S]

Bob, I haven't experienced that in my cars. Perhaps you had a faulty component somewhere or some bad connections?

 

[capetonian]

The TD gives the red light whenever the revs fall below 1000 to 1100 - the ammeter shows a load of 12 V + once the revs reach 1500. I was told this is pretty normal. Maybe it's the same on B's?