The weakest link (thing that gets the hottest) on an HF45 hybrid is the generator. Everything else stays cool as a cucumber. I've pushed it to the limits 50 or 60 times on really hot days. Never a warning chime, light, message, or code. But I've come close.
Oh, once BACKING UP a trailer uphill...
Get an OBDII scanner.
My eCVT
runs 145°F not towing and 155°F when towing 3200 lbs uphill on a 99°F day.
Anyone have a concern with 155°F?
This, specifically, is the temperature of the Mercon ULV transmission oil.
Every hybrid on the road has a transmission oil cooler. Here is a drawing of...
The engines NEVER overheat in a hybrid. Not sure this is needed.
Example: I have towed a 3200 lbs high profile travel trailer up a 6% mountain grade on a 99°F day and the engine never went past 215°F which is mild.
Way in the green zone.
And air conditioner was running too!
Key is slow down...
Sounds like either / or both remedies would work.
Sounds like current draw of your trailer is too small. Resistors or adding additional LED lights or a single incandescent light would solve this.
Also sounds like the reason for the software recall was to modify the current to detect a trailer...
Sure. Why not.
Usually it will last something like 7-10 years (depending on use of course).
Less in cold climates.
If the signal weakens as battery voltage drops, your connection "may" (or may not) may not last as many years.
But if it's handy for you, I see great utility in what you've done. 👍
Update:
Been using parking lamps or headlamps almost every drive since April.
My battery has stayed 100% charged since.
(It will drop to 96% overnight and maybe 94% over a long 3 day weekend.)
So it's apparent (again) that the trucks stay awake in the first 1-2 hours after parking and lose...
The fan "trick" is to change it from discharging or sustain, to actually charging.
The fan "trick" is to boost from 12.7 to 13.9 volts or more.
So yours is at 13.9 by coincidence for some other reason.