Back in the early 70's I was often travelling to Alaska, Fairbanks, Pt Barrow, and Anchorage. Most of the hotels had outside electric outlets for plugging in water jacket heaters, etc. It don't take me more that one winter to realize that didn't suffice.

I would go out in the morning to start the car and drive away only to discover that the power stearing was inop due to the fluid being thick as jello, same with the ATF. So I adapted. I would go out and start the car , go in and have breakfast, and by then the PS fluid and ATF would have thawed out enough that the car was serviceable.

Going to the movies in the evening..??

All the cars for blocks around were left with their engines idling for the duration of the movie or dinner "out" and a movie. Ice fog "cloud" above the city.

So yes, I do not own an FEH nor any close equivalent, a "classic" Pruis, only. A Prius for which I am not the primary driver, even.

The facts of the Ford patent I mentioned are available for anyone to read.

Would you downshift a FWD automatic with the streets as slick and icy an I have often seen them in Alaska..??

I thought not.

Absent Ford's use o ftheir own patented technology that's exactly what an FEH might feel like if you just simply lift the gas pedal and the hybrid battery is in serious need of charge.

I have little doubt that a 2005 FEH might not have an OAT sensor, and might not use the patented technique. But my suspecion is the '05, like many cars, might have an OAT sensor but no driver display.

But, not to argue the point, a bit of reading and you will find, for instance, that the Escape's F/awd system has been changing and evolving from day one. Originally a true part-time 4WD system, manually or automatically engaged, automatically only for 15-20 second periods.

Then it evolved to the use of a rear electromechanical clutch in order to vary the coupling in accordance with the driver's actions and roadbed conditions.

That proved to be problematic, the PTU begin failing right and left due to overheating from driveline stress.

So now the only form of awd capability left to the FE and FEH is TC, Traction Control. You won't need to read very far, or much, on the 'net, to discover the horrible shortcoming of that technique.

 

 

Transient: Hear, hear! Good post.

I made what I thought was an innocuous posting with some reasonably good info from my experience. I wouldn’t have a regular car without a block heater and given the design of the FEH, I think it’s even more important.

Next thing I know…

 

FEH battery has 4-5 bars and not have to six bars. The IMA battery control module(s) allows the battery to overcharge.
Occasional overcharging is a desirable function, but too many frequently repeated cycles of overcharge can damage the IMA battery.
This damage is the result of excessive current and heat build up.
Unique local topographical and ambient conditions in affected states, combined with a driving cycle that typically keeps the IMA battery fully charged, creat this potential problem.

 

In reading recent posts on this “Block Heater” issue I came across a post by wwest:

“My advice for operating an FEH in the wintertime in Alaska would be to disable, drop, one front halfshaft, provide a CONSTANT 12 volts to the rear driveline clutch and install a resistor in parallel with the OAT thermistor. You'd have a dramatically SAFER FEH for wintertime use and since ALL regen would be at the rear drive wheels there would be little need for sub-freezing OAT detection.”

How nice of him to give such advice. But in the end this is really poor advice. It
demonstrates his complete lack of understanding of the engineering involved in these
cars.

Should there be someone out there who considered that to be workable advice: forget it,
it’d be a really, really dumb thing to do.

BTW: I don’t see an OAT thermistor in the wiring diagram. I suspect, if the system
measures OAT at all, this is done by reading the Cylinder Head temperature immediately on startup.

Also: OAT is irrelevant to the battery charging issue. Only battery temperature itself is
relevant and that is measured by the FEH system.

 

These days almost every HVAC system has an OAT sensor.

 

Look for Ambient Air Temperature Sensor in the index. Location shows to be in the front grille area on the LH side.

How could they possibly use cylinder head temperature to calculate ambient air temperature??? They do use it to calculate engine coolant temperature though!

 

The 2005 does NOT have this.

 

Okay, if a '05 doesn't have that AAT sensor, all AC units must have a built in sensor to keep condensation from freezing.

 

Yeah, they do. There is an evaporator air temperature probe.

Mine turns on the A/C compressor at 45 degrees and it turns off at 41 degrees like clockwork.

However, it has been as cold as 30 degrees outside, and it still runs the compressor but infrequently.