AGM batteries mixed with FLA batteries

Hello,

So I have a 2020 International LT with a factory installed MaxxForce eAPU system. I’ve read that the system calls for 8 AGM batteries to work efficiently. The previous owner, I’m guessing either didn’t know or just didn’t want to spend the extra money on AGM’s. So he or she placed 8 FLA batteries in the truck. These were the cheap $100 batteries. When I purchased the truck, I changed out 4 of the 8 batteries to AGM batteries because I just brought them on 6/1/24 and it was 7/29/24 when I purchased the truck. Everything worked up until recently I have started to encounter that when my eAPU is turned on, it will do as I want until the programmed settings of 12.3 volts reached. The truck starts to begin the charging process. My eAPU shuts down as it should and my front HVAC system should turn on. Sometimes this works falsely. But more frequently, the blower knob doesn’t work. I can turn it all the up or down but still won’t work. The vents start blowing hot air and won’t shut off even if I turn the blower knob off. The directional knob works as should. The only way to stop this is that I have to turn off the eAPU, start the truck and let the batteries charge back up at a consistent 14.0 volts. So my questions are;

1. Will changing out the FLA to AGM so that entire battery bank is AGM’s as recommended by Navistar the solution and could the improper charging be the problem?

2. Since I brought the AGM’s on 6/1/24, they have been used continuously since I brought them, is buying 4 new AGM of the same battery brand Interstate 31-AGM5’s from the Love’s, OK to make the entire battery bank Interstate 31-AGM5’s OK given the battery age and use?

3. Could my issue be the climate control module itself that needs to be replaced?

The AC/Heat works as it should while the truck is idling and when I drive. The problem only occurs while using my eAPU and parked. There no issues with the eAPU as it works as it should. The only issue that occurs is when the eAPU is active, once it hits 12.3volts, the truck starts to recharge the batteries and the eAPU shuts down, the truck HVAC systems does as explained above.

I’m really thinking this is a battery issue and not a faulty HVAC issue such as compressor, blower motor, evaporator, etc.

 

I took this picture to better explain my original post. It’s dark to illustrate how the blower/fan speed knob is off, the temperature and directional knob is illuminated. As it does this on and off cycling, it’s blowing hot air out the vents which cannot be turned off.

 

Right now I’m doing a test while I wait for the Love’s shop to open. Current voltage is 12.6-12.5 volts. The lower voltage is when the eAPU AC compressor cycles on. Once the AC compressor cycles off, the voltage goes to 12.6 volts. It will continue to do this until 12.3 volts are reach which then shuts off the eAPU and the truck will start. Nevertheless, as shown in the picture, I notice the control module on the dashboard does as shown in the pictures. The front vents are blowing heat while the back vents are blowing cold air. I can smell and feel the heat. This why I’m guessing it’s electrical and possibly due to improper charging due to the mixed battery types. Because the problem is progressing worse, I want to take care of this issue before major damage occurs. The dealership wants $750 just to diagnose the issue and they say it’s ok to mix battery types.

 

Ok thanks

 

I’m sorry, please explain the one buss and where this located. I’m at the Love’s now getting the FLA’s changed to AGM’s. The AGM’s will be all the same, same brand, same type. I hope this buss item isn’t fired.