I have been chasing a gremlin.

6 months ago the ABS module had to be replaced. Needed to be towed as I had also zero brakes didn't have time to troubleshoot and learn how to make the repairs myself so I took it to the dealer. Then 3 months ago 12v battery died so I replace the battery. During the cold months I always noticed a drop in fuel economy 37-38mpg vs 40+ during the summer) but now it was down to ~33mpg during cold weather. I noticed the engine temperature struggled to get to normal, so I replace the thermostat and water pump. Seemed to work. but then the battery died (again). Seemed to take a charge ok, but when I tested the system (with the battery charged) it did NOT appear that the battery was being charged. I noticed that the voltage at the batter actually went down when in the "run" mode.

Ran a diagnostic and it returned a P0662 04-28. I reset the codes, but the code came back immediately. I checked the start-up voltage at the b+ terminal, and there was an initial 13.8v charge being sent to the battery, but it ended after a second (maybe less) and did not cycle to charge the 12v system again.

I have looked tested the fuses with ohms meter. no open (blown) fuses. No shorts to ground detected, no corrosion at any of the terminals.

I am leaning to change out the DC to DC inverter, but before I commit a S-ton of $$$ for a new one, wanted to see if anyone out there may have something I may have missed. (spent hours on line searching this one, no joy)

All help appreciated.

Capt. K9

 

Good Morning Capt,

Would like to offer suggestion or two, unfortunately not all Ford vehicles are the same , so can you provide ;
Year,,, model,,, miles on speedo . Some charging systems are computer controlled and they differ from year to year, thanks

 

2011 hybrid fusion,170000 miles

there is no alternator. There is a DC to SC inverter. And that is where I M guessing the issue resides. Not sure, my code reader only goes so far, and I don’t trust our local dealer.