APU Tri-pac not charging batteries

I've replaced the alt with a new one from eb electrical. It looks like the old styled bosch alt. I kept getting the alt code still. Replaced fan with a thermoking fan it's the black one that doesn't matter if it's running clockwise or counter still got alt code. Than replaced belt still alt code. Got a second alt still alt code but not as quick. Tested the new alt passed load test. Checked alt while running with multimeter pushing 14.07 when a.c. no kicked in 13.98 when kicked in and slowly decreases to 13.89 or 13.88 than the alt code came uo. Checked batteries they are charging to 13.41 up to 13.5. Still getting alt code. Replaced ground wire with a new one and still getting alt code. I'm running out of ideas. I've got the older model tripac before the evolution it's a 2012. Any help would be appriciated.

 

Ok so I was looking at the voltage on my inverter it showed 12.9 so got under the apu checked the voltage from alt which was at 13.79 than shut off with alt code.

 

I put a new ground wire on it I thought it could be the hot wires that's why I load tested the batteries with the apu running

 

Load tested batteries and they were fine. Than tested alt again and it was giv8ng 12.7 I'm stumped

 

I'd start with the simple stuff, like look for crusty terminals on the main battery cables. The corrosion gets inside the terminal crimp and eventually crawls up the wire under the insulation. When you put on new terminals, use the heat shrink with adhesive to seal them. On both the battery and apu end.

On the apu end, the battery cable connects to the starter and is a booger to get to. The main power to the alternator also connects to the starter. Not a big deal to just replace all those ends since some are pretty tough to get to in the first place. A hydraulic crimper can be had on eBay for under $50 and well worth having around.

A 2012 should also have a 50A maxi fuse inline inside the engine case, that could also have crusty terminals.

All that said, the 0.5V drop between the apu engine and batteries, then also between batteries and inverter is a little high, but isn't that unusual if the cable run is long enough.

I've never seen an alternator reading decrease while running like that unless there was a drive belt or pulley issue, which would have been pretty obvious by now. Or some kind of load on the unit that exceeds the alternator's output. Like running a microwave and a coffee pot at the same time off the inverter. The battery voltage increasing kind of tells us that it isn't a load problem. A loose pulley or belt would be making some noise. Bad terminals would cause some unpredictable behavior, so that would be the first thing.

The regulator has two wires. One just jumps to the B+ post, the other goes back to the control board (sense). Might even be worth looking at those connections too. Look for loose or dirty terminals in the regulator connector, and maybe just crimp on a new ring terminal for the B+ connection just to be sure. Or get a repair pigtail from Thermo King or an eBay dealer.

There are repair manuals you can find with a Google search. They have wiring and control board diagrams. There are three versions of the control board, so make sure you choose the right one. It's a fair guess a 2012 will have the latest version, 1.5 if I'm not mistaken. They're easy to tell apart from the fuse and relay arrangement. You could even open the lid and reseat all the fuses and check the tightness of the screw terminals pretty easy as well.

Pack your patience and take the time to cover the details. Sometimes these things can be tough to find. I chased an intermittent shut down problem for nearly a year and finally found the culprit that I never imagined. This was on an 04/2006 production, original version zero board. That failed solder joint (on the back of the board and not visible) was randomly interrupting the run relay causing the apu engine to stall. I discovered it accidentally by happening to press on the control board in the right spot while the engine was running and could recreate the stall.

 

is simple check the connection on the alternator

 

Mine broke down I was replacing the alternator when the connection camo off, a dealer wont tell you, due the vibration and humidity I did replace the switch and connection, haven't had any issues ever since

 

I'm having similar situation with my tri PAC, it can run all day and doesn't charge batteries, now I'm getting a alt 3 code. I have pulled covers and went over with fine tooth comb. Found two broken wires on back of alternator, however I have spliced one wire, and replaced the other, I've come to the conclusion that alternator needs replacing, I went into thermo king two months ago with this problem, they told me that the clutch on compressor was bad, even though I had the same code, so $1400.00 and two months past, back to square one, only now unit only runs approx two mins then kicks off. Shopping for alt other than a thermo king Brand. I was told that 120 amp is a different wire or heavier wire, with that said I think that a 90 amp will be quite sufficient. Using same size wires. Plan on changing out within next two weeks

 

I just did the Chevy alternator conversion. The only thing I had to do differently was to reuse the 3.1” TK pulley and fan and an extra washer behind the fan to keep it from rubbing on the case. The 1 1/2” Chevy pulley put too much of a load on the motor when using the coffee pot and would cause it to want to die and smoke like a locomotive.