Installed BIG 3 AND Now After Got Severe voltage drop

[frenziedhstge]

So I installed my BIG 3 upgrade tonight and when I was all done installing it I noticed something very strange. I only will get 14.3 volts if the heater in the car is on or if the head lights are on. If either of those are turned off the voltage will drop to 12.5 with the car running and with no music playing. I thought this was very strange. Anybody have any ideas on why my voltage is at 12.5 when the car is on with no heater or headlights, but once you turn the headlights or heater on you can literally watch the volts jump from 12.5-14.3 in a matter of a few seconds and as long as the heater or headlights stay on the voltage will remain a constant 14.3

I'm guessing a ground issue from battery to chassis?

Any ideas guys I have a few ideas in my head not enough never ran into a problem like this before.

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[BOOMINGRANDPA 5,000+ posts]

i'm gonna wait for those answers too before i do mine lol.. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[wew lad 5,000+ posts]

start checking voltages at various points, they should all be the same

my bet is that you have a PCM controlled alternator in your car, what car is it? I bet a newer honda or toyota

 

[wew lad 5,000+ posts]

another possibility is that you were starving your heater/ac/lights before the big 3 so they saw ~10-12v and your alternator still saw 14.4v so you also saw 14.4v

now that everything sees the same voltage you're seeing the equalized voltage (or the correct voltage)

 

[frenziedhstge]

i'm gonna wait for those answers too before i do mine lol.. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

The ideas I had were loose bolts, checked that they are on there just fine.

The other idea I had was moving the batt to chassis ground to another part of the chassis or even grounding to to alt.

 

[frenziedhstge]

the car is a 2017 Hyuandi Tucson.

 

[frenziedhstge]

start checking voltages at various points, they should all be the same
my bet is that you have a PCM controlled alternator in your car, what car is it? I bet a newer honda or toyota

I did test the voltage at several places with the heat and head lights off and it was 12.5 all around with car running.

 

[frenziedhstge]

I did test the voltage at several places with the heat and head lights off and it was 12.5 all around with car running.

Then when I turned the heat and headlights on I tested again with a DDM and it was 14.3

 

[BOOMINGRANDPA 5,000+ posts]

I did test the voltage at several places with the heat and head lights off and it was 12.5 all around with car running.

***** man i got 14.8 at idle without big 3..

 

[frenziedhstge]

start checking voltages at various points, they should all be the same
my bet is that you have a PCM controlled alternator in your car, what car is it? I bet a newer honda or toyota

It does appear that I do have a PCM alt I just did some research on a lot of Hyunadis and all of them have it. I was just reading up on bypassing them but would that even be ideal?

 

[frenziedhstge]

Yeah more research I did it appears that people with PCM alts are having the exact same issue low voltage with accessories off with big 3 and once they turn accessories on like headlights or heater the voltage goes normal in the 14.3-14.7 range.

 

[frenziedhstge]

I think I answered my own question. after researching PCM controlled alts this is the conclusion i've made when i turn the head lights on or heater on in the car the volts jump from 12.5 to 14.3 cuz at that point the alternator kicks on cuz its sending a signal to the ECU that the alternator needs to start charging. So I've come to the conclusion I either have to bypass the PCM or get a VCM

 

[BassDrop]

I think I answered my own question. after researching PCM controlled alts this is the conclusion i've made when i turn the head lights on or heater on in the car the volts jump from 12.5 to 14.3 cuz at that point the alternator kicks on cuz its sending a signal to the ECU that the alternator needs to start charging. So I've come to the conclusion I either have to bypass the PCM or get a VCM

Happens the same with my truck. 12.3 volts most of the time.

 

[frenziedhstge]

Happens the same with my truck. 12.3 volts most of the time.

Did you bypass the PCM or get a voltage control module? I'm just really worried about voltage drop as I'm probably pushing close to 2000wrms. I read some articles of people that added a second battery and it did nothing with PCM alts that adding a second battery wont even cure the problem with the PCM since the second battery isn't being controlled by the ECU so the alternator will not kick on unless it receives that signal from the ecu.

 

[Jeffdachef 5,000+ posts]

tuned in. My **** doesnt charge at all until 800-900 rpm, my idle is 600 rpm.