Is there a way to turn off rear defroster on remote start?

[Yellowknife]

More starts with less charge time.

Agreed. So in addition my understanding is that Ordinary cars in general can experience undercharged batteries if repeatedly driven short distances only, particularly in cold weather.

In sub-zero weather, lead-acid batteries require about 15 minutes of driving to internally warm up enough before they can accept a good charge. Voltage regulators are calibrated to start charging at higher voltage when cold, then drop as the battery warms up to prevent electrolyte loss.

In addition, having high drain accessories on like a rear defogger, seat warmers and heater blower etc. leaves less alternator output available for charging the battery.

Basically cold starts/short trips can take more charge from the battery than you’re replenishing up here in particular as I've seen for decades first hand. Eventually, the draw of accessories, cold starts etc. cause a shortfall in recharging until the battery hits a critically low level, and the car won’t start.

As expected some will argue otherwise. This is from my first hand experience with countless examples of it. Same with folks up here who don't run their engine's long enough to raise the oil temp enough to remove condensation in extreme cold. They end up with water in their engine's and complete engine failures even though they're doing regular oil changes.

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[Yellowknife]

If you don't want the window to defrost, and it's -40⁰, I'm assuming you don't need the rear wiper either. There's an electrical plug for removing the hard top, just unplug it altogether. I think the can bus may even sense it's unplugged and not turn on automatically but I haven't tested that theory.

Another good suggestion - I forgot about that even though I take the hardtop off in summer sometimes. I'll have to test that out. We don't have freeze/thaw cycles up here most of the winter. It's just too cold. So at most I have to brush a dusting of snow off the back window. Not once have I needed a scraper for it even with the rear defrost connection busted. Never use the wiper either. The heated mirrors I like though as they do frost over. Come to think of it their activation is tied to the rear defrost switch aren't they?

 

[Dyolfknip74]

Agreed, so i'll get it fixed but pull the fuse for it since I don't want it turning on in the cold on remote starts, per the previous suggestion.

There is no point in pulling the fuse, it isn't drawing any power. The button light may come on but there isn't any power going anywhere. At best, put some electrical tape over on the broken cable for the slim chance of it shorting itself.

 

[Yellowknife]

There is no point in pulling the fuse, it isn't drawing any power. The button light may come on but there isn't any power going anywhere. At best, put some electrical tape over on the broken cable for the slim chance of it shorting itself.

Right. I meant after it is fixed. Might as well get it repaired under warranty even though I don't use it, just to not leave it broken. But I also like the wiring disconnect idea better than pulling a fuse now as suggested above, same as when pulling the hardtop off since I don't use the wiper or rear wash either. It also has to go in for the driver side door lock switch no longer working, and the transfer case shifter still being stubborn to engage after 3 years with no improvements despite being told it would "break in".

 

[Dyolfknip74]

Right. I meant after it is fixed. Might as well get it repaired under warranty even though I don't use it, just to not leave it broken. But I also like the wiring disconnect idea better than pulling a fuse now as suggested above, same as when pulling the hardtop off since I don't use the wiper or rear wash either. It also has to go in for the driver side door lock switch no longer working, and the transfer case shifter still being stubborn to engage after 3 years with no improvements despite being told it would "break in".

Ahh ok. Ya, that's best bet for sure.

Weird about tcase though. They usually wear in quite quickly.

 

[mwilk012]

Agreed. So in addition my understanding is that Ordinary cars in general can experience undercharged batteries if repeatedly driven short distances only, particularly in cold weather.

In sub-zero weather, lead-acid batteries require about 15 minutes of driving to internally warm up enough before they can accept a good charge. Voltage regulators are calibrated to start charging at higher voltage when cold, then drop as the battery warms up to prevent electrolyte loss.

In addition, having high drain accessories on like a rear defogger, seat warmers and heater blower etc. leaves less alternator output available for charging the battery.

Basically cold starts/short trips can take more charge from the battery than you’re replenishing up here in particular as I've seen for decades first hand. Eventually, the draw of accessories, cold starts etc. cause a shortfall in recharging until the battery hits a critically low level, and the car won’t start.

As expected some will argue otherwise. This is from my first hand experience with countless examples of it. Same with folks up here who don't run their engine's long enough to raise the oil temp enough to remove condensation in extreme cold. They end up with water in their engine's and complete engine failures even though they're doing regular oil changes.

That simply isn’t how it works though. The alternator is just going to put out more current as necessary to supply the loads. You could label it a fuel savings, I suppose, as the energy ultimately comes from increased fuel usage.

 

[Yellowknife]

That simply isn’t how it works though. The alternator is just going to put out more current as necessary to supply the loads. You could label it a fuel savings, I suppose, as the energy ultimately comes from increased fuel usage.

If what you say is how it should work on paper, I am conveying that it doesn't at our temperatures. There's plenty of professional literature to back it up but I'll leave it at that.

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