battery light problem

[Anubis_4_99]

Ok so Im having a problem with my charging system and its very confusing.

I can go a couple weeks without my battery light coming on, then there are days like yesterday where it comes on within 5 minutes of driving everytime.

My dash and head lights will all get brighter, then they will dim down, and the light will come on.

My battery has been tested and is good, my alt was tested and checked out as good (external test). I replaced it anyway because its under lifetime warrenty and I could.

My terminals are new and clean, I see no visable breaks in any related wiring.

With the less then 3 hour old alternator my battery light has come on again. One thing I did notice is when my lights dim I seem to loose power driving, and when they brighten up I regain it.

If anyone has some insight I would really appreciate it.

 

[TurboATM]

this sounds like what happens when the alternator belt breaks and stops charging...maybe something to do with the wiring to the alt? try checking that connection

 

[tenn-gsx]

Do the N/T have the alt relay? If so that can cause the symptoms mentioned.

 

[Anubis_4_99]

Belt is new, I've checked all the wiring I can without pulling the harness apart and so far so good. Ill be taking it down soon for some attention so ill check the rest when I do, any suggestions are welcome.

Ill check on the relay idea, not sure myself if they do or not.

 

[CODE4]

What are your running voltages when this happens? The voltage regulator is built into the ECU unfortunately, so when it fails, the only option is to either replace the ECU, or use an external voltage regulator to take over (but you will have a permanent battery light on). The battery and alternator can check out fine, but if the voltage regulator fails then your system voltages will be excessively high or low.

Check out the External Reg offered by Symtech that standalone megasquirt users install. I have been using one for years now.

 

[Anubis_4_99]

What are your running voltages when this happens? The voltage regulator is built into the ECU unfortunately, so when it fails, the only option is to either replace the ECU, or use an external voltage regulator to take over (but you will have a permanent battery light on). The battery and alternator can check out fine, but if the voltage regulator fails then your system voltages will be excessively high or low.

Check out the External Reg offered by Symtech that standalone megasquirt users install. I have been using one for years now.

i don't know the amps but it charges at a steady 14.3V. i can take both posts off the battery when this happens and it will still hold a rock solid idle.

the guy at the parts store suggested the voltage regulator as well, he seemed under the impression it was in the alt though.

is there any way i can test the ecu before replacing it? ohming out pins or whatnot? because there are a few in the local yard and I'd also like to test them before putting one in cause there $30 and no returns.

another thing i have noticed is it seems heat dependent. today it was nearly 100, and now that it has cooled off it hasn't come on all night, and driven nearly 40 miles.

 

[Anubis_4_99]

well the light has come on again for the last two or three days.

i took it to oreilly and had them check the battery, and the alternator output.

constant 14.3 volts charge, battery checks out at 13.1 (shows 100% charge on the tool and passes test as good) and amps are at 85 (90 amp alt).

so everything voltage wise checks out. battery and alt are both new, alt is less then a week, battery less then 3 months.

its been suggested that my terminals could be a culprit (auto-parts guy) but i can take my battery completely out of the vehicle without causing the battery light to come on, so i have a hard time believing that is the issue.

posts and terminals have been cleaned and tightened as well.

like i said in my previous post, the only thing i notice that is a constant factor is heat. if its hotter then hell outside i tend to get a battery light, if its bearable its about a 70/30 chance that it stays off.

also may be relevent to mention i noticed my dp gasket is blown and causing my under hood temps to be hotter then i believe they should be. thats on order as no one local had it in stock near me.

anyone have any more ideas?