Voltage drops while driving.

[AcuraTL03 10+ year member]

stock battery up front 2 1/0 runs to the rear. 1+. 1-. HC2400 in the back

Well today i noticed that while I am driving my volt meter would read 12.x sometimes with no music playing. When im idle i rest at 14.3. I drove around the block a few times and while accelerating i would i drop to low 12s to 13. If im coming to a stop or slowing down it would go back to 14.3.

Is my alternator dead or somthing? All my connections are tight and secure. I mean when i start the car it goes to 14.3 so I dont think its dead right? and with the car off its sitting at 12.4 - 12.7.

Also whats a good H.O alt company???? I have a stock 120 amp alt right now. Id like an 200 or 220 amp alt. thanks all

this is all with no music playing

edit:just got back from driving around the block again. Well while driving i was at 12.6 volts... going like 30 35mph. I parked and i was sitting at 14.1. i played a song full tilt on my powerbass xa1500. i was dipping into the 13.x but never hit 12.x volts. But as soon I put my car in drive and drove off i went into the low 12s.

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[mlstrass 5,000+ posts]

your PCM might be shutting the alt off for fuel economy. I know some Honda's do that....

 

[NASTY08IMPALA 5,000+ posts]

yes and alot of.gm do that too ..i know my impala did before i got a ext voltage regulator

 

[AcuraTL03 10+ year member]

Thanks for the input guys. Well i removed my kinetik hc2400 and unpluged my amp. I drove to work with no voltage drop. Hmm the kinetik was also resting at 12.8 when i checked this morning. And i let me stock battery upfront sit for a few hrs not hooked up to the car. It was resting at 12.7 so both batteries are reading fine

 

[jteske88 10+ year member]

i would say its the pcm, most cars that have and obd2 port have some sort of battery saver, hell my car will full charge then run off batt. i can see 12.8 when its at lowest operating point.

 

[AcuraTL03 10+ year member]

i would say its the pcm, most cars that have and obd2 port have some sort of battery saver, hell my car will full charge then run off batt. i can see 12.8 when its at lowest operating point.

What does pcm stand for? How do i go about fixing this? Just get a new alt? I had a couple of different amps bwfore my powerbass. All 2k+ amps and never had this problem. I did go to the drive in movies and had my car on with out the engine running for a couple of hours if that makes a differwnce .

 

---------- Post added at 08:49 AM ---------- Previous post was at 08:49 AM ----------

 

i would say its the pcm, most cars that have and obd2 port have some sort of battery saver, hell my car will full charge then run off batt. i can see 12.8 when its at lowest operating point.

What does pcm stand for? How do i go about fixing this? Just get a new alt? I had a couple of different amps bwfore my powerbass. All 2k+ amps and never had this problem. I did go to the drive in movies and had my car on with out the engine running for a couple of hours if that makes a differwnce .

 

[jteske88 10+ year member]

The pcm is the cars computer, i can have it tuned out on mine. not sure about your platform. new alt with external reg to hold voltage. cause there wont be anything you can do unless you have the tuneing programs for your car.

 

[n8skow 10+ year member]

PCM issue is sounding likely.

You might also want to check for belt slip or a worn pulley on the alternator itself (which would be more noticeable when theres a good draw on the electrical system).

Have you heard any squeeling when you accelerate or the electrical system is under load? Do you have a black powder/residue around the alternator housing?

 

[AcuraTL03 10+ year member]

PCM issue is sounding likely.
You might also want to check for belt slip or a worn pulley on the alternator itself (which would be more noticeable when theres a good draw on the electrical system).

Have you heard any squeeling when you accelerate or the electrical system is under load? Do you have a black powder/residue around the alternator housing?

Thanks for the response. No there isnt any squeeling noise coming from the engine bay. I checked my batteries resting voltage during lunch, its sitting at 11.9 with the car off. Now i know that is a very low reading. is it considered dead? When i start my car it sits at 14.1 with car on, at idel.

 

[n8skow 10+ year member]

In that case - sounding like a bad battery.

Get it load tested.

 

[mlstrass 5,000+ posts]

In that case - sounding like a bad battery.Get it load tested.

x2 resting voltage really doesn't mean much, need to see what they do under a load. Any auto parts place will test them for free...

 

[audiobaun 5,000+ posts]

Its the Honda issue with the charging system.//content.invisioncic.com/y282845/emoticons/fro.gif.c695f1f814b01c4ad99fe7f8cccadd29.gif

 

[AcuraTL03 10+ year member]

Thanks all for the help!! would getting a new alt fix this problem? I have 400 to spend on an alt, could you guys throw some names of a few good alt companies.

I dont know why this is happening now, i mean i had previous systems before in the same car nd i never droped to 12 volts while driving. Especialy while not playing music at all. Oh and the starter battery in fine upfront, but im still gonna switch it out for a g34 diehard platinum.

Now on to the new alt. Is it just plug and play? My girls uncle works at honda i guess i could get him to do the labor for me. Would he have to change anything in the ecu/pcm with the new alt?

Sorry for all the questions please answer if you have the time

 

[NASTY08IMPALA 5,000+ posts]

if u get a alt with a external regulator it will bypass the voltage drop from pcm..i got a mechman 240 with the external regulator it works great...the alt is about 400 and the reg is 125 or so

 

[maylar 10+ year member]

PCM = power control module. One of the numerous computers on modern cars. The voltage on my Buick is all over the place too, sometimes under 13V.