Alternator not charging correctly

98 tacoma 4X4 2.7 engine. I put in an aftermarket alternator. Charges fine puts out about 14.35@ 2k rpm. Problem when driving is that the headlights and heater fan will get stronger at around 2k then drop back down again after rpm drops. Changed alternator exact Same problem. The battery is only 7 months old. Alternator keeps the battery charged. Anybody have any thoughts

 

poor Quality After market remans. The second one was the same brand??

7 Month old batteries can and do fail.

Have you checked the voltage at the headlights at idle?? Battery voltage at idle??

i can only think at 2000 rpm and above your getting the 14VDC plus rpm drops the voltage is reduced.

The same for your blower motor is this on the direct speed not through the resistor

 

I would suggest starting with connection checks and corrosion checks first. Remove any connectors, clamps, grounds etc and check for green death.

It sounds like a bad alternator, but you need to have it and the battery tested properly to rule them out.

 

Two different brands same effect. Bat voltage at idle a out 12.5 no lights or fan

 

Just funny that if it the alternator two bad ones in a row

 

Ive had bad ones out of the box make me question my sanity. Ended up finding a local electrical shop that rebuilds them and tests them.

Who knows what standards china has.

 

I guess you know that's low.....

Every connection as @Bishop84 suggests. And have the alternator tested at a local electrical shop if your community has one.

 

Anymore that seems common.

 

IT varies from day to day!!

Mom and Pop auto electrical shop for the win every time.

Though with a little experience it is easy to learn to fix alternators and starters

 

Think I found the problem. At idle speed fully loaded the alternator is only putting out about 11.7. That explains why the lights blink. Think I got an alternator problem. Thanks for all the input

 

You can get a decent Denso reman at the dealership's online store for a fair price. It's cheaper than buying the Denso parts and rebuilding it yourself. They even took my aftermarket core without complaining.

 

Glad you were able to figure that out.

Reman electric parts can be very poor quality as of late.

local rebuilder if possible. Remanufactured Denso from your Toyota dealer of choice.

 

Update. Factory new alternator. Charges the battery a constant 12.86. Obviously not a good charge . But when I disconnect the positive terminal and take the alternator readings directly from the alternator it reads as it it should. But with the positive terminal disconnected as soon as I turn on the headlights the car quits. Pulled the alternator and had it bench tested and it tested perfect. wondering now if I have a battery problem. Bit it also tested good. Anybody have any thoughts

 

Do you still have the original alternator? If so have it rebuilt.

 

Check out the "1st gen 105 amp bolt in alternator" thread. Denso part #

$177 210-0461 Denso First Time Fit Alternator - 210-0461

210-0461, from a Suzuki Grand Vitara.

Edit~ 1st gen thread

 

You really don`t want to be removing battery cables on computer controlled engines!! While running!!!

Everything has been tested but the cables Might be time for an upgrade !!

Once the system voltage drops to low the ECM shuts down in a self protection mode .