(Installed )370a mechman alt & 4800 Xs battery & big 3 upgrade

[Chevy*808*]

Got a chance to install the 370a mechman alt along with the XS 4800 and also did the big 3 on my 2018 Premier Tahoe . Installation was pertty simple thanks to Tony from mechman .

Alternator came with the 1 yellow wire harness & p103 module for the stock alt plug .tap in to the police accessories since for the yellow wire.


After all that what done voltage was at 14.9


It was running fine couple days after installing the alt.wife drove it to work at the stoplight half way to work the battery saver showed on her dash . She said it was driving fine no problem ac cold / headlights & fogs / radio etc Was working fine but she notice the voltage on the dash was around under 14 give or so with with the battery saver mode display on the dash.


I check when she got home .Check all the connections .thinking something got lose .check the p103 module if it’s came out was fine .battery terminal was fine . Everything seem fine .turn it on there was no battery mode display .check the voltage it was around 14.3 it pertty low if you ask me .


Let it seat for couple day .cold start it was 14.3 disappointing.with ac on highest setting headlights & fog light one voltage reads about the same on ideal .Now sure what’s the problem.i message Tony Friday Jsut waiting for his reply on Monday . Did any of you guys installed a big alt on your 2015 & up Tahoe/Yukon ? Any problems Lmk guys what to fix this problem before I start ordering my sound system .

 

[Xsbank]

Check your battery specs, a fully charged battery should be getting ”about” 13.9 volts so that means the load is light and the alternator is correct. Starting the car should take about 1/2 amp or so (500 amp/hrs for a second or two) so there isn’t much power needed from the alternator to top the battery. Also, how old is the battery? Lead acid batteries deteriorate over the years and so yours may be telling the Reg that it’s happy.

Also, 370 amps with a single belt and stock wiring? Seriously?

I see your battery is going on 4 years old, it’s near the end of its life for an Oem battery.

 

[Eddie Rivera]

Got a chance to install the 370a mechman alt along with the XS 4800 and also did the big 3 on my 2018 Premier Tahoe . Installation was pertty simple thanks to Tony from mechman .View attachment 359475

Alternator came with the 1 yellow wire harness & p103 module for the stock alt plug .tap in to the police accessories since for the yellow wire.
View attachment 359481

After all that what done voltage was at 14.9
View attachment 359482

It was running fine couple days after installing the alt.wife drove it to work at the stoplight half way to work the battery saver showed on her dash . She said it was driving fine no problem ac cold / headlights & fogs / radio etc Was working fine but she notice the voltage on the dash was around under 14 give or so with with the battery saver mode display on the dash.
View attachment 359478

I check when she got home .Check all the connections .thinking something got lose .check the p103 module if it’s came out was fine .battery terminal was fine . Everything seem fine .turn it on there was no battery mode display .check the voltage it was around 14.3 it pertty low if you ask me .
View attachment 359479

Let it seat for couple day .cold start it was 14.3 disappointing.with ac on highest setting headlights & fog light one voltage reads about the same on ideal .Now sure what’s the problem.i message Tony Friday Jsut waiting for his reply on Monday . Did any of you guys installed a big alt on your 2015 & up Tahoe/Yukon ? Any problems Lmk guys what to fix this problem before I start ordering my sound system .

Any updates? I'm looking to add a mechman to my suburban and don't want any issues. Is the p103 module what keeps the voltage from going up and down?

 

[BlackZ71-15]

I was told all the negative wire have to go through the RVC sensor.

 

[JuanFajardo]

I was told all the negative wire have to go through the RVC sensor.

Ive heard the same, still trying to figure out how to connect a dual battery, does the new ground from the second battery have to go thru the RVC sensor, on PPV they just ground it to frame and possitive to starter ! Been trying to figure it out, some body please help lol

 

[BlackZ71-15]

Ive heard the same, still trying to figure out how to connect a dual battery, does the new ground from the second battery have to go thru the RVC sensor, on PPV they just ground it to frame and possitive to starter ! Been trying to figure it out, some body please help lol

I'm not a 100% certain, but I would imagine the new ground would also need to go through it as well. Yeah, I definitely wish there was more info on it because I would like to eventually add a second battery myself. I say run it through the RVC and see what happens

 

[Chevy*808*]

Any updates? I'm looking to add a mechman to my suburban and don't want any issues. Is the p103 module what keeps the voltage from going up and down?

Just need to add another ground to the farme .voltage is good

 

[Joel_S]

The p103 is to allow the factory harness to think the oem alt is there. I have one on the way for my wife’s Yukon xl. The yellow wire is turning on the alternator. The RVC is bypassed by using the p103.

Basically this system allows you to use a standard GM 4pin alt instead of a newer 2 pin with RVC.

it’s the easiest way (imo) to add a second battery and upgrade grounds and everything else wire wise inside the engine bay as you don’t have to run your second battery grounds through the RVC.

OTHERWISE, you need to route your positive and negative from the drivers side battery (second battery) over to the pass side and make sure your ground passes through the RVC sensor.



OP, your battery looks older and like it’s probably nearing the end of its life. Would suggest replacement before checking much else, especially if yours is a SLA battery.

Edit, didn’t see you only had the one ground. I had assumed you had upgraded those as well already.

 

[rick1024]

I just installed a 400a mechman and a big three upgrade. I am also getting battery saver messages, but everything seems fine. no idea what is causing it. same p103 and i tapped into the windhseild wiper motor fuse with a fuse tap

 

[BigPac]

Any good pics of the "big three" wire locations, grounds , routing ect