Hi I have 2007 hummer h3 that have around 83k miles. I used to have a remote start and security system. They got taken off the car I start to get a msg saying service charge system. I have aftermarket battery terminals I took off the fuse box and checked the wires there everything looks good. I checked under the steering wheel nothing touching or stripped. I took the car to auto zone they did battery and alternator test. They said my alternator failed the test but I still don’t think it’s the alternator cus the battery charges fine. The car start fine no problem and it just started after the security system got taken off. So maybe there is something touching somewhere or shorting? I made a research and found that door jam switched might cause this issue. Is that correct? Any ideas on how to figure this out?

Thank you

 

Put a meter on your battery, should be @12.5v+resting. While keeping the meter attached(clamps or stick probes in terminals) turn off all accessories and start it up. You should get 15v+ on startup, then after a few minutes, should drop to 13.5v.
Post the results.

 

resting is 12.77
when I start it it’s 15.38

and after few mins it fluctuate between 13.43 to 13.53 then to to 13.50 for few seconds then fluctuate a little

 

Fluctuate a little? Run for a few more minutes, turn on all accessories, looking for the low end reading.
Also, scan and post the codes.

 

with all accessories are on and headlight and all I am getting the lowest is 14.35 for like a sec then it go up again and fluctuate and highest is 14.47 they fluctuate in seconds

and scanned for codes. No codes no check engine light

 

What scanner are you using?

 

auto zone have scanner and they scanned and there was no code

and I have fix it obd scanner and I got no codes as well

 

You need a scanner that will scan Generator Battery Control Module (GBCM)
Whatever, I will guess the code B1390 and/or B1492?
Test at Under Hood Fuse Block (UHFB) fuse 32.
Test at C125 terminal 16 Orange wire.
Trace wire from C125 to GBCM terminal C, look for open wire.

 

Easy stuff first. The most common cause of SVC Charge System is loose battery Terminal Connectors. You did not share what aftermarket brand you are using, but they can become loose where they connect to the battery cable too. Then comes cable corrosion, then look at the Battery and charging system.

 

I checked they are not lose I totally forgot the brand but they are very nice ones and the problem didn’t happen until the remote start got taken off