Voltage drop when accelerating

[Hobourable88]

Hello. I have a 2013 Subaru Impreza sport. Recently replaced my valve body. Installed an all in one aftermarket coolant/cvt/oil temp reader. I've noticed since after changing valve body that my voltage drops to 12.5V when I'm cruising and increases when I lift of gas pedal or push the vehicle on a hard run or under load when my headlights are on at night back to 14.1/14.2V. Tested battery and alternator and auto shop says both are fine. Can anyone give a reason for this?

 

[bmart]

You don't want it to work properly? I'm confused.

 

[Hobourable88]

You don't want it to work properly? I'm confused.

I do want it to work properly. I was asking if it's normal for voltage to drop to 12.5v when cruising. I'm of the opinion that normal running voltage is between 13.8 to 14.3

 

[bmart]

Voltage changes a lot depending on what current the car is drawing (amps are pulled, not pushed) and the charging state. Yours sounds normal to me.

 

[Rattlenbang]

12.5 sounds low to me. Where are you measuring the voltage?

 

[bmart]

And if you're using a crap cheapo meter...don't. they're always way off. And if your meter battery is low, your readings will be way off.

 

[Hobourable88]

I'm using a meter which plugs directly into the obd port. It receives power once the vehicle has started. I also verified with a volt meter that was plugged into my cigarette lighter port and they read the same as well.

 

[Rattlenbang]

Bad grounds and connections can cause voltage issues even though battery and alternator are good.

 

[Hobourable88]

Will verify my ground wires

 

[Rattlenbang]

If it's dropping to 12.5 volts at moderate speed that power is being lost somewhere.

 

[Hobourable88]

Which is what I'm trying to figure out. When I life off the throttle and decelerate, the voltage climbs back up to normal. Which is odd. When I'm on full load with my headlights on, voltage never drops no matter how I drive.

 

[pfarmer]

Will verify my ground wires

Do you a after market ground from the negative terminal directly to ground? If so you may have bypassed the battery condition sensor.

 

[Hobourable88]

I have no aftermarket ground wires

 

[bmart]

Tell us about your meter.

 

[Hobourable88]

This is what I use. Purchased it on Amazon.

 

[bmart]

I would get a real, quality meter on it. I have meters from Harbor Freight and Amazon and they're all WAY off from reality. Find someone with a Fluke with a new battery is in and check the voltage with the care off, idling, and at rpm.

 

[Rattlenbang]

When you deaccelerate your engine is drawing less power, so less voltage drop. You really need to use a scan tool to monitor voltages.