1994 hilux overcharging. Have done everything!

[Josh_cjr]

Hey everyone hoping you guys could help or even point me where to look.

Basically I got stranded one day as my battery was killed due to overcharging battery. Now I have changed battery, alternator and the external regulator all done professionally. The auto electricians have also had a look and could not see what would be the issue but have changed the plugs just in case. It still overcharges, not all the time it's intermittent like some drives its fine and some it will start overcharging. Really have no clue what's going on.

[trentmeyer23]

Were these all replaced with new or used components?

[Josh_cjr]

Were these all replaced with new or used components?

all brand new.

[Manxman]

Overcharging ==the alternator is not being propperly regulated. This can be because the battery is faulty, bad connections, maladjusted regulator, wiring fault or bad alternator.

Battery nom charge volts 14.2 max nominal open cct 13.6V Normally flat at <=10.x volts open circuit.

Normal cranking voltage, ~8V - as the battery fails, this will drop and it won't crank.

Battery needs to be large enough to absorb charging current, or the voltage will rise and cook the battery. Diesel motors need >650CCA batteries. Petrol > 450CCA. Battery MUST have enough electrolyte, have minimal sulphate in the cells and no internal shorts. It MUST hold charge for at least 2 weeks @ >=20deg C. or 1 week @ 5deg C Extreme cold kills car batteries, overnight if they're weak/old. Batteries should fit to the limits of the battery box, and ideally, be Japanese or Australian made. Korea, Thailand and seveal others are usually poor quality construction.

regulator on your model is external relay type? that means it's adjustable.. Not many would know how to do that these days?\.

Bad connections -any green residue on or under batt terminals/charge wire needs washing away with water and a spare toothbrush. dry batt with toilet paper & discard it & brush. All coonections should be clean and bright metal contact faces. Contact areas must be as large as possible, pref flat. Charge wire from regulator must have full thickness for whole length without break or thinning.

Alternator - bad brushes cause a lot of problems, usually no charge tho'. Bad bearing cause polling-which is destructive. Both are cheap easy fixes. Bad diodes cause low outputs/permanent discharging. Diodes should not be expensive, but are often heavily marked up compared to TV/Radio diodes, even allowing for the higher power. The slip rings on the rotor shaft do wear, but clean up on a lathe at least once, bad slip rings ==no output.

report any defects/results from above pls.

[trentmeyer23]

How are you determining that it is still overcharging? What diagnosis has been done?

[Manxman]

It's an old car. ign switch failure is normal at this age esp if heavy keyset hanging from lock. Check car for no dischrge when key off, except immobilizer/clock

[Josh_cjr]

How are you determining that it is still overcharging? What diagnosis has been done?

That's what my multimeter says and my volt gauge.

[trentmeyer23]

If the sense wire voltage has too much resistance then the alternator will likely charge at a higher rate in order to compensate.

[Josh_cjr]

If the sense wire voltage has too much resistance then the alternator will likely charge at a higher rate in order to compensate.

is there a way i can test this?

[trentmeyer23]

Resistance test using a multimeter. Are you able to provide a picture of the alternator connections?

[Josh_cjr]

Resistance test using a multimeter. Are you able to provide a picture of the alternator connections?

would have to be tomorrow but yea. just some more info, now that i have a volt gauge in the car i was driving it around and testing different ways to make it stop. a good way was to stop the car and turn it off. after doing so it went back to normal. still sounds as it could be the sense wire??

[trentmeyer23]

What model Hilux? Could possibly still be the issue, definitely worth ruling it out.

[Josh_cjr]

What model Hilux? Could possibly still be the issue, definitely worth ruling it out.

1994 yn85r

[Manxman]

Sense and charge wires: make sure wire not bent sharply, that it is in good condition-not frayed, dirty or reduced in cross section at ANY point. Make sure all connections clean and bright where they touch another part-including the connectors on the wires. Repair as required. Resistance error might only be very small, & not measurable without a bare wire and contact Wein-Bridge system for real accuracy, and a low voltage source. A digital Ohm meter has at least the last digit +-1 error, moreso on low ranges, and you need better than that accuracy IMO.

if your battery is undercapacity, it will overcharge because the regulator has limited performance, and cannot regulate the entire alternator output if the battery is removed/too small. If it can crank the motor at ~8v, it's prob good and large enough. The longer it can do that the better. If cranking voltage is >9V then battery is too large, which can cause problems.

If crank voltage is <=6V, battery is too small/too flat, damaged or sulphated (old). Even that may be too low on some vehicles.

Edited June 29, 2015 by Manxman