Big 3 Troubleshooting

[Echo]

Hey all. I recently did the big 3 upgrade, but I'm running into a strange issue.

I have a dual battery setup with a battery isolator installed, which works just fine. At the same time that I did the big 3, I also upgraded my alternator from a 130 amp to a 250 amp. Before doing this, I had a voltage readout of 14.2 volts at idle. Now I'm getting between 14.7 and 15 volts, which seems a bit high for just idle. Additionally, the red battery indicator in the message center keeps popping up intermittently. I'm pretty sure I did the upgrade correctly (Alternator+ to battery+, Battery- to chassis ground, and Alt. Ground to Chassis ground) and I did not remove any of the stock wiring. I used a 4g OFC kit from Sky High Car Audio, and a BNR Parts 250 Amp High Output Hairpin Alternator. I don't understand why the battery indicator keeps coming on, am I missing something?

Its a 2002 Tahoe.

 

[Echo]

SOLVED: The issue was with the LAMP signal wire, otherwise known as the L Terminal Circuit. GM did not implement RVC (Regulated Voltage Control) in their 1500 platforms until 2005, this means that the voltage was controlled by a regulator built into the alternator, rather than the PCM itself. Adding a higher output hairpin alternator and big 3 wiring was causing a P1637 code to appear, and the battery error indicator to flash, although I'm not sure why it does this specifically. To solve this issue, I learned that the Lamp (L) wire needs to be spliced into and connected to the 10A Ign E fuse in the under hood fuse box with a fuse tap, using a 10A fuse on the bottom, and a 7.5A fuse on top. This can be achieved either by buying a H104 Indicator Light Harness (96-04) from Mechman Alternators, by tapping the Lamp line directly with a length of wire to the IGN E fuse (not recommended), or by creating your own harness. I made my own harness because I had the resources already at my disposal to do so, and because mechman wants $30 USD for it. Doing this stabilized my voltage and eliminated my P1637 code, shutting the battery warning indicator off. Mechman sells their alternators with that harness, but because I bought mine from Ebay, and it is not Mechman brand, it did not come with the harness.

I hope this helps anyone who may run into a similar issue.

 

[Fless]

Any pics of the harness you made?

 

[Echo]

The 104 Harness has all 4 of these wires, but I only needed two of them, the Brown (F) Field Wire , and the Blue (L) Lamp Wire. The fuse tap comes off of the Lamp Wire. The female end goes to the factory alternator connector on your Tahoe, male end goes to your alternator.

 

[Echo]

Here is the diagram I used for building mine. You may need all 4 wires, or just 2. If you face the back of the alternator, your 4 wires from left to right are PLFS. Pulse, Lamp, Field, and Sense. Lamp will be the spliced wire on the harness. It's important to note that you do not want to connect it to a constant 12v source. IGN E is the safest source for your fuse tap.

 

[black1970]

The battery went dead on my 2007 Tahoe which it has not done in a long time. After recharging my XM radio will not work. Called XM and after all they could do they said take it to a dealer. Took the ground off but didn’t help. What gives? BTW I can still get XM on my I pad.

 

[Echo]

The battery went dead on my 2007 Tahoe which it has not done in a long time. After recharging my XM radio will not work. Called XM and after all they could do they said take it to a dealer. Took the ground off but didn’t help. What gives? BTW I can still get XM on my I pad.

Wrong thread i assume? Check your radio fuse, and there is possibly another fuse on the back of the actual head unit. I would start there. I would reccommend making a seperate thread in the 07-14 Audio & Electronics section though.