Battery Light ON, Intermittent No Start - Trouble shooting help?

The battery light came on in my 05 Tacoma (Manual, 2.7L 4 cylinder, RWD, SR5) about 2 weeks after I just installed a new clutch release cylinder. I replaced the original starter and battery about 8 months ago.

Checked the voltage and it was:
Overnight: 12.5V (spec below says 12.5-12.9V @20C or replace)
Running (no load): 13.74V (spec below says 13.2-14.8V)
Running (load): 13.55V
After turned off: 12.74V
25 mins after off: 12.60V
1 hour after off: 12.50V

Went to PartSource and the battery and alternator (generator) tested good, battery was 690/700 CCA. I read on here that it could be a diode in the alternator and people have driven for 3 years with the light on. Drove it for 2 weeks without issues and was waiting for normal alternator issues so I could bite the bullet and replace it but seemed okay...

Two days ago the temp dropped to -15C (5F) and in the morning truck wouldn't start. Checked the battery and it was 12.1V. Took the battery out and got it tested where I bought it and they said it tested bad and gave me a replacement.

Installed the new battery today, light still on. Also cleaned and verified the connections to the alternator, grounding points, engine ground, battery terminals, battery to frame ground point (and upgraded this wire to 4GA.) Checked the fuses and all tested good, continuity and low resistance.

With the new battery voltage was:
Running (no load): 13.74V (spec below says 13.2-14.8V)
Running (load): 13.55V
After turned off: 12.74V
25 mins after off: 12.44V
1 hour after off: 12.24V (spec below says 12.5-12.9V @20C or replace..???)

Followed the attached trouble shooting section of the service manual but I don't have an ammeter to verify the charging circuit... working on getting one ASAP. Doesn't seem clear to me it is the alternator, almost seems like it could be the new battery too. There are no parasitic loads or after market accessories on the battery.

Truck started about 90% of the time today, few times it wouldn't start on first turn over. When it wouldn't start it the starter wasn't engaging, no sound or noise at all but clock would go out showing the truck was trying to start - seemed like a dead battery and voltage would show around 12.0-12.2V which would make sense. Verified the clutch penal safety switch and starter circuit and it all seemed good. Started fine this evening, even with battery reading 12.0-12.2V. With the alternator putting out 13.7+V I am surprised the new battery isn't holding a charge... could the alternator be putting out the right voltage but not the right current??

Anyone have similar issues?? Advice before I throw down $250 on a new alternator??

Thanks in advance!!!

 

Any service experts able to give me some pointers?? Thanks in advance

 

Trouble shooting again today if anyone has some advice or experience. Thanks guys!

 

A couple of things to check. You said you dont have a parasitic draw but mentioned a drop in the battery voltage after 25min. When the truck fails to start you mentioned that the battery voltage was 12.1. You should have heard something like it was trying to start. We are talking about two different electrical systems and with a perfectly good battery it should start regardless of the alternator. I would start with doing a voltage drop test. With your multimeter set on V dc place the black lead on the battery positve (on the battery and not the connector) and the red lead on the heavy positve wire going to the starter (center of the stud). Aligator clips work well to hold the the test leads on. Crank the motor and read the voltage drop on the meter. You should have less than .1v per connection. Do the same procedure for the ground side of the circuit. On lead on the negetive battery post anf the other on the starter case (clean shinny spot). Sand a spot of the starter if you have to. This will tell you the integrity of the starter circuit load side. Post your results or PM me directly.

 

Thanks Ruggybuggy but it is actually starting fine now, I think it was the clutch safety switch.

I am troubleshooting the battery light... trying to verify the alternator is the actual cause when it seems to be charging fine. I believe the parasitic load was the interior light, left the door open while testing. I am going to perform the same voltage checks but make sure there is nothing drawing current.

Would the voltage drop test make sense for the alternator?

 

Checked the voltage today (about +2C) and it was:
Overnight: 12.21V (spec below says 12.5-12.9V @20C or replace)
Running (no load): 14.02V (spec below says 13.2-14.8V)
Running (load): 13.88V
After turned off: 12.74V
25 mins after off: 12.41V
1 hour after off: 12.38V

Trying to find a cheaper ammeter to check the current. Any other tests you recommend?

 

You could do one from the battery positive to thr B+ on the alternator but you'll probably wont find an issue. Did you check the negetive ground cable on the motor for corrosion? Also the smaller body ground wire that bolts to the inner fender on the left side next to the battery. Becase your alternator is charging, your voltage is higher than battery votage while its running you may have a bad diode in the rectifier, pulls one phase to negetive. Lots of places like Autozone do battery testing for free. Most of those hand held testers they use can test the charging system. See if you can get them to do the test for free. The tester will pick up if you have a failing retifier pack and will fail the alternator if its not delivering the proper amperage (with and without loads). Be sure to check your wiring before you have the test done. Not a good thing to buy an alternator and discover a lose wire.

 

I checked and cleaned the positive leads, stud and connector on the alternator positive, the ground to frame (both from the battery and the small ground from the alternator) and the ground to engine, wire brush and light sand paper where required. All had some slight corrosion and looked to have never been disconnected since new.

Checking positive from alternator to positive on battery was 0.04V.

I also brought it to Partsource (like AutoZone) last week and the battery and alternator passed their full testing, they said perhaps a bad cell in battery. Brought the battery to where I bought it and the guy at the counter seemed new, he "tested" the battery and said it failed for cranking amps (saw him input CA and not the CCA) and he gave me a free replacement under warranty.

Perhaps I could try another location or shop to test the alternator again... was hoping to be able to perform a further tests in my garage.

 

Battery voltage on a battery will fall after its been charging. A fully charged battery will read about 12.7 and a 75% charged battery will read 12.5V. Try disconnecting the negative on the battery for the same period of time and see if the voltages drop the same amount. I suspect you may have a draw. An easy way to tell without an ammeter is to take off the negive battery post and run a test light in series with negative cable. Does the test light come on? The brighter the light the larger the current draw. The smallest bulb in the test light should be used to detect small current draws. Remember that the the modules in the truck need time to "sleep" so check the light after a half hour. Some modules can take up to 22min to sleep.

 

Your Canadian, eh? Me too, I suspected when you mentioned 2°C. When the guy at Canadian tire tested the battery at CA it would have definitely failed but a least you no the battery is good. Unlikely you have two bad batteries.

 

Yessir, fellow Canuck! Checked and it doesn't seem like I have any draw... truck has started fine and the battery hasn't died but the battery light is staying on which is the problem I am trying to solve. I picked up almost new Fluke ammeter from an electrician buddy and verified the current of the alternator.

The measured output current of 12.8A @ 2,000 rpm with no load is over the spec of "10A or less" as per the manual... I am wondering if the alternator is outputting too much current and this is the cause of the battery light. What do you think? Perhaps this should be a new thread?

From the service manual:
7. INSPECT CHARGING CIRCUIT WITHOUT LOAD
(b) Check the charging circuit. (1) Maintain the engine speed at 2,000 rpm and check the reading on the ammeter and voltmeter.
Standard: 10 A or less for amperage 13.2 to 14.8 V for voltage
MEASURED AVERAGE: 12.8A @ 13.8V

8. INSPECT CHARGING CIRCUIT WITH LOAD
(a) With the engine running at 2,000 rpm, turn the high beam headlights ON and turn the heater blower switch to the HI position. (b) Check the reading on the ammeter.
Standard: 30 A or more • If the ammeter reading is less than the standard amperage, repair the generator
MEASURED AVERAGE: 38.9A @ 13.6V

 

Just went to start it to go to a buddies place and it won't start. Going to try the starter troubleshooting again tomorrow... Didn't think I would need to bring it to my mechanic but I am close.

 

I think you may have two separate problems. My best questions would be a bad diode in the rectifier of the alternator causing the light to come on. Have someone check the charging system. Do a voltage drop test on the starter circuit. Also when it doesn't start check for 12V on the control side of the starter. The small wire on the starter will have 12V when the key is turned to the start position. When your trying to start the truck does it make a click noise or does it do nothing?

 

Bit the bullet and changed the alternator and belt tonight... battery light is out, runs nice and quiet with the new belt. And it has started the 3 times I have tried since changing it.

It has started the last 11/12 times. The one time it wouldn't start it didn't make any noise, , the starter wasn't firing up or engaging at all. Next time I'll try and take a reading on the starter... just changed it last year and lost my receipt, paid cash of course. A+A Auto won't honour the purchase so thats another $180 with tax but probably required soon enough.

And the project after that is going to be the interior blower fan rebuild... already removed it, cleaned it with vacuum and air and installed a new filter. Reading on here it seems replacement blower fans make the same annoying ticking noise noise after a season or two.

 

And for anyone interested the new alternator reads 14.3VDC @ idle, 14.4VDC at 2,000rpm, and 14.1VDC under load @ 2,000rpm.

 

Bad diode.

 

The intermittent start was a bad ground to the starter I think. Took the entire system apart, bench tested everything and everything passed... put it back together and it has been flawless for 3 days.

But the ticking fan doesn't seem to be an easy one. Replaced cabin filter, vacuumed it out, even tried a new blower motor and it still ticks.

 

"You think", a voltage drop test on the ground side would have confirmed if there was an issue.