Battery light on with car off

hssnpny · Dec 21, 2008

What would cause the battery light to remain on with the car off, key out? The battery light goes out as soon as the key is turned to ignition on, and stays off when the car is started. It comes back on again when the car is turned off.

Also, in related news, I've had a problem the last 3 days with the battery dying overnight. I charge the battery back up, it runs great, but it's dead again the next day. I don't know if the battery light has been acting this way since the trouble started or not . . . I just happened to notice it today.

Thanks for any info.

HISSIN50 · Dec 21, 2008

Check the regulator wiring.

The theory: Ignition power goes through the battery light (and a 500 ohm resistor in parallel) and on to the I terminal of your regulator. Check to see if the I terminal is receiving constant 12 volts (key off). If so, pull the loom and look for shorted A and I terminal wiring. I dont think you'll find this but rather that either your regulator or alt (diode issue) are acting up. A bench test of the alt should tell the story.

If you need a new reg, it takes 2 mins to swap one (just FYI).

The battery light being on non-stop could be enough of a parasitic draw to cause the battery to drain. You can do a draw test (meter set to amps, placed in-series between the disconnected neg battery post and terminal). Be sure all dome lights and everything are off.

Post up results and we can post more direct info for the given issue.

Good luck.

Stevejr · Dec 21, 2008

Another thing you can do is stick a test light in series thought the neg bat cable like hissin was sayin and the light should not be very bright if lit at all. If it is lit you can start pullin fuses till ya find out which circuit it is.

hotcobra03 · Dec 22, 2008

just following

ive read both replys and following green/ red stripe wire from terminal I ,i see it goes to battery lite than it runs to accessory terminal on ignition switch...when he said with key in hand the lite was on.. .what can he do for that end of power to check for problem?

hssnpny · Dec 22, 2008

Thanks for the replies.

I'll have to check out the wiring as mentioned. Since the blower kit relocated the alt to the bottom of the motor, maybe some debris kicked up and mangled the wiring. That location never did strike me as a good idea.

Just to understand better . . . they can do more extensive testing on a bench test than the in the car test?

I did try my meter to check for draw. The car has an alarm, which when battery power is reconnected, immediately goes off. I mean to say this is normal operation. When I connected my meter in series between the neg battery terminal and the neg cable, I only heard a momentary blip out of the alarm, then nothing. So maybe I cooked my DMM trying this. I also noticed a pretty good spark when reconnecting the neg battery cable to the battery . . . so maybe there's a pretty good draw going on. Guess there would have to be to kill the battery overnight.

Checked voltages across the battery, 12.5 not running, and 13.8 to 14.0 while running, so those seem ok.

I'll post back one of these evenings when I get the car elevated a bit, to check the wiring.

Thanks!

HISSIN50 · Dec 22, 2008

Your voltage does sound good.

For the draw testing, I'd either disco the alarm's power source or be sure it stays off (if it arms passively). Most alarm sirens draw less than 2 amps, so that should not have fried your meter - even cheap meters generally have a 10 amp DC ammeter, and a fuse on the circuit.

What were you reading when you did the parasitic test? With most meters, you have to repeg the positive lead and be sure to set it to the ammeter setting.

The bench test removes your vehicle wiring as a source of issue. If you desire to test the circuits with the alt in the car, the I circuit should show 1 volt or above. The B terminal floats battery voltage, give or take half a volt, and the S terminal should float about 1/2 battery voltage.

Hotcobra03, the issue with the excite circuit being hot is probably either a short to the sense circuit or a bad regulator (the latter is more likely).

hotcobra03 · Dec 22, 2008

learner

HISSIN50 said:
Your voltage does sound good.

For the draw testing, I'd either disco the alarm's power source or be sure it stays off (if it arms passively). Most alarm sirens draw less than 2 amps, so that should not have fried your meter - even cheap meters generally have a 10 amp DC ammeter, and a fuse on the circuit.

What were you reading when you did the parasitic test? With most meters, you have to repeg the positive lead and be sure to set it to the ammeter setting.

The bench test removes your vehicle wiring as a source of issue. If you desire to test the circuits with the alt in the car, the I circuit should show 1 volt or above. The B terminal floats battery voltage, give or take half a volt, and the S terminal should float about 1/2 battery voltage.

Hotcobra03, the issue with the excite circuit being hot is probably either a short to the sense circuit or a bad regulator (the latter is more likely).

most test show are bench testing,his discription was without car running
ok hission50,with his car off and key in hand his I terminal should read 0 volts at alt. than than terminal A should have 12 volts... than inside of regulator is where you have found most problems,, now would that be enough current to lits the battery lite without a complete circuit.and can he cut power going into regulator and the lite would stay lit if it was ingnition switch sticking causing the complete circuit.

hssnpny · Dec 22, 2008

HISSIN50, when I tried the parasitic test, I never got a reading on the meter. The quick blip out of the alarm was sub-second in duration, after which the meter was toast. And I did re-peg the positive test lead and select amps for the test. Gotta say I think in the 15 years I've had that meter, first time I've checked for amps.

It should have occured to me to disconnect the alarm . . . but come to think of it, I don't ever recall seeing where they put the box. Is there a typical location for it?

HISSIN50 · Dec 22, 2008

hotcobra03 said:
most test show are bench testing,his discription was without car running
ok hission50,with his car off and key in hand his I terminal should read 0 volts at alt. than than terminal A should have 12 volts... than inside of regulator is where you have found most problems,, now would that be enough current to lits the battery lite without a complete circuit.and can he cut power going into regulator and the lite would stay lit if it was ingnition switch sticking causing the complete circuit.

No, he cannot unplug the regulator and have the light stay illuminated, unless there is an wiring anomaly.

Under normal circumstances, the regulator provides a ground path to the I circuit when the alt is off but the alt receives the signal to excite, or when system voltage is below ~10.5 V. As the alt excites and output bumps up, the ground pathway is removed from the Excite circuit and the light goes off.

HISSIN50 · Dec 22, 2008

hssnpny said:
HISSIN50, when I tried the parasitic test, I never got a reading on the meter. The quick blip out of the alarm was sub-second in duration, after which the meter was toast. And I did re-peg the positive test lead and select amps for the test. Gotta say I think in the 15 years I've had that meter, first time I've checked for amps.

It should have occured to me to disconnect the alarm . . . but come to think of it, I don't ever recall seeing where they put the box. Is there a typical location for it?

No typical location, though under the driver's side dash is common. You could trace the siren wiring back through the firewall and find the box that way. Normally you can simple set the alarm off (disco' the siren) and listen for the internal relays in the box clicking.

On your meter, check the fuse (sometimes you have to unscrew the back cover on the meter - check the instructions). It doesnt sound like you had a large draw going on there................ (most alarm sirens I've used were 20 Watts, or equate to having like a 1.67A draw).

hotcobra03 · Dec 22, 2008

hot at all times?

HISSIN50 said:
No, he cannot unplug the regulator and have the light stay illuminated, unless there is an wiring anomaly.

Under normal circumstances, the regulator provides a ground path to the I circuit when the alt is off but the alt receives the signal to excite, or when system voltage is below ~10.5 V. As the alt excites and output bumps up, the ground pathway is removed from the Excite circuit and the light goes off.

your answer sounds like maybe i didnt ask right... when you say Excite ,alt has to be spinning ,yes..? terminal A is always hot..? terminal I needs volts to lite up battery lite,,,than when alt starts to spin ,terminal I circuit becomes open...and battery lite goes out,, but if car is off and nothing spinning terminal I should not have volts,, now he says lite is on so volts should be at terminal I , if regulator is bad ,as you feel is most common,,he cant just pull power from battery that feeds terminal A,and see if lite is still lit...,,or did i miss something here completly...im following from book and see everything you are saying and it helps alot to understand ,, my pics are great but it done with the thought that the tech knows all the basic already...

Battery light on with car off

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