Bad electrical issue? Need help.

**SDGTP99** · 09-02-2015

Ohkay, so when I'm stopped at an intersection my cars MPH needle starts to bounce around, the radio volume goes up & down & cuts out and the battery voltage drops and if my headlights are on they dim and the car won't move. Only thing I've done to my car recently is clean the battery terminals and replace the positive battery clamp. The car was doing this every once in a very blue moon before I replaced the clamp. Now, it's getting worse & happening nearly every time I stop the car. Any thoughts, comments or suggestions are welcome. This is my DD & I need it fixed asap😅

**stealthee** · 09-02-2015

Sounds like voltage regulator is going out on alternator.

**SDGTP99** · 09-02-2015

That's an answer I would've never expected. Is there a way to test that?

**stealthee** · 09-02-2015

Advance should be able to test it with it on the car. The reason I said that is you mentioning the voltage dropping. When voltage drops all sorts of strange things can happen to the electrical components of the car. It all goes hand in hand.

**SDGTP99** · 09-02-2015

And it just so happens Advance is where I got the Alt, just last spring.

**SDGTP99** · 09-03-2015

One more question. Can the voltage issue cause the transmission to seem to shift funny? I don't remember.

**91parkave** · 09-03-2015

Yep

**stealthee** · 09-03-2015

Most definitely.

**SDGTP99** · 09-03-2015

Thank you guys for the replies! You've been a big help.

**SDGTP99** · 09-05-2015

Just happened to notice if I keep my foot on the gas at idle I have no problems.

**stealthee** · 09-05-2015

Increased RPMs equals increased voltage....

**SDGTP99** · 09-07-2015

Had the Alternator tested and it passed. Hmm.

**SDGTP99** · 09-16-2015

I've had Advance check the Alternator 2 times now and all they could tell me was something is draining the battery. At a dealership now having the PCM scanned.

**SDGTP99** · 09-16-2015

Ok so. Finished the scan & the only current codes are for Tire Pressure Sensors. In History however I had U1000, U1301, U1096, U1088, & U 1064. I looked up those codes and couldn't find out what they mean. My car now experiences all these problems while driving and shifts funny frequently. So is my problem really an Alternator going bad & it's just not testing bad?

**HighOctaneRacing** · 09-16-2015

I agree with Stealthee. I remember you made a post about what alternator you should get and we recommended an OEM one from the junkyard but you went to advance. There should be a warranty on that so I would just make them warranty it regardless what their tests say and go from there.

**SDGTP99** · 09-18-2015

^^^I might have to do that.

**Spawne32** · 09-19-2015

Originally Posted by SDGTP99

Ok so. Finished the scan & the only current codes are for Tire Pressure Sensors. In History however I had U1000, U1301, U1096, U1088, & U 1064. I looked up those codes and couldn't find out what they mean. My car now experiences all these problems while driving and shifts funny frequently. So is my problem really an Alternator going bad & it's just not testing bad?

Electrical issues can cause funny things to happen, the U codes are "universal" codes, often times MFG specific codes, but typically are an indication of data communication errors, and often times a result of rapid voltage fluctuations (voltage drop and restart of the module) or the imminent failure of a module or ECU. U1301 is a Class 2 circuit short to battery, U1000 is a communication failure between the ECU, U1096 is loss of communication with the instrument cluster, U1088 seems to be related to invalid data from a suspension control part, likely the stability control (EBCM), U1064 Loss of Communications with DIM.

Check your battery voltage with a multimeter with the car not running, if your less then 12.5v @ rest, replace it, if you have access to a load tester, be a good idea to see if its able to support the proper amount of cranking amps, and making sure the battery doesnt have a bad cell. The voltage regulator in the alternator could be problematic yes, but generally speaking they dont cause these codes, these are a result of a dead short in the system somewhere causing communication failures.

**Spawne32** · 09-19-2015

Also should be noted, that I have heard issues exactly like this as a result of a faulty battery current sensor (acdelco 13505369 for 5v supply from BCM, 10306471 for 10v ), it might be worth it to replace that and see if it helps with the issue, seeing as how the part is only 11 dollars.