You can buy a container of desiccant to keep in your car. As others have said, use the AC. Not just when defrosting, but after to continue removing moisture.
Alternatively, I’ve found thermite will easily remove window fog.
What do you mean by the “defroster”? The rear window one?
The front windshield defroster. IOW the “defrost” setting on your heater/AC controls. Back in the day when cars’ controls had words, not pictures, that was/is what it’s called.
And one of the things that happens when that setting is selected is that the AC compressor runs to dehumidify the air before the heat is applied to it to make it hot. That dehumidification step is a large part of how the defrost setting does its magic.
You are quite correct, but I will pick a tiny nit here. If it is cold enough the compressor won’t come on as there will not be a high enough pressure in the AC system to trigger the low pressure switch. Since the outside air is already colder than what the AC system would cool it to, no compressor.
Ah, the picture of the windshield – got it!
Yea, verily. Mine won’t switch on at 40°F or under, says the car’s manual.
I wonder if I could sue for a million five if it doesn’t come on at 41°.
No as it would probably just be a little low on charge. 
Apparently filling a sock with kitty litter and leaving it on the dash when you park it makes a big difference.
Is the kitty litter a desiccant? If so putting a bottle of damp rid in the car would help. I don’t know if it attracts enough moisture though.
I’m pretty sure setting it to DEFROST overrides any temperature sensors and engages the AC compressor for the reasons stated.
Something to remember: There are actually two somewhat different processes going on. **Defrosting *the outside of the windshield and defogging the inside of it. Defrosting the outside refers to melting solid ice crystals that have formed on the outside and only involves applying heat (from the inside-out). Defogging refers to evaporating condensation that has formed on the inside and involves both applying heat and dehumidifying, hence the need to run the AC system regardless of the temperature. Rear window defoggers use only heat but they work because of the large amount of heating wires spread out across the entire window, something you obviously can’t do with the front windshield. Also, because all car occupants face forward (and are always at least in the front seat) the rear window doesn’t fog as easily as the windshield.
Also remember that, especially if you have a lot of people in the car, the AC compressor will have to continue to run (via the defrost setting, although less often) to maintain low humidity otherwise even once the defrosters blow hot the inside of the windshield will fog up again because the human respiratory system is basically a ‘humidity engine’.
*****About 30 years ago Ford came out with an all-electric front windshield defroster/defogger system that could clear a solid sheet of ice in like two minutes. It was expensive, problematic, and only served a niche market so it was discontinued in the US. Although pretty rare now you can sometimes see old Ford cars with them, the whole windshield has a ‘gold’ tint to it.
Alas, not in my car. In winter the light on the A/C switch blinks to tell me to get stuffed, then turns off, no matter where the air-direction control is set and whether the selector is set for outside air or recirculation.
From the manual:
The manual contradicts itself. Elsewhere it says the A/C won’t turn on if the temp is beneath 40°F (bolding in the original and nothing removed in or between the two paragraphs except the settings icons):
No amount of punching the switch turns the A/C on when it’s too cold to turn on automatically.
You have two competing systems here.
First off the AC system dehumidifies the air by cooling the air. This is done by circulating the air over the evaporator which is cooled to about 32F (varies slightly with various systems). You can’t make the the evaporator much colder than 32F or instead of dripping off the water condensed out of the air would freeze solid across the face of the evaporator and prevent any air from flowing.
The system has (depending on design) pressure switches, pressure sensors, temp sensors on the evaporator, or a regulating valve the responds to temp on the evaporator. These systems are designed to maintaining the evaporator temp at the magical 32F number. The evaporator may get as warm as 40F or as cold as maybe 28F for a short period of time but it will average 32-33F
Now in addition to that you have a AC control that is wired to turn the compressor on in defrost.
So let’s say it’s 35F out. You flip the system to defrost. The AC control head says compressor on. The signal has to go through the temp regulating system for the mechanical portion of the system. At 35F the temp and pressure in the system is so close to the desired temp of the evaporator the compressor does not energize.
Kenm in your case I suspect your system is low on charge and as a result the pressure in the system is lower than expected causing the compressor not to engage at temps above 40F.
I hope this clears up some of the confusion in this thread
I didn’t say the A/C doesn’t work above 40°F. I joked that I’d sue for $1,500,000 if it didn’t work at 41°F.
I quoted the car manual that in one place says the A/C will work above freezing, but in another places says the temperature must be above 40°F.
But that’s incidental to the point of the post. Hail Ants said the A/C should work on the defrost setting, which would override the temperature sensors. I quoted the manual saying the A/C in my car wouldn’t do that.
But I don’t think any vehicle A/C would work in the winters here, where it frequently drops to –30°F and colder (air temp, not wind chill) in January and February, never mind the freezing point.
When the temp drops below freezing, then continues down until the thermometer bulb breaks, who cares if the A/C doesn’t work?
I’ll be dammed if I can understand your comment that the manual contradicts itself. It clearly does not.
In one area it says the AC works at above freezing temps with no value specified. This is a true statement.
In the other section it says the the AC only works above 40F. This is also a true statement and does not contradict the previous statement as long as water does not freeze at 41F or above.
To pretend otherwise is picking fly shit out of ground pepper.
Above freezing means a temperature above 32, which means at most, 33. It won’t, according to the same manual. Your snark is like saying the air conditioner works when the temperature is lower than that of the surface of the sun, so that isn’t wrong either because it does. Take a pill.
Cite that above freezing means at most 33F
A course (opposite of fine, in case you object to the use of the word) jump of exactly one Fahrenheit degree from 32.0, rather than listing an infinity of decimal-point numbers above 32.0 to forestall snark about fractions of a Fahrenheit degree above the freezing point; i.e. your example of pepper and fly shit.
Sorry “My post is my cite” is not a cite.
So for the majority of the world that uses Celsius above freezing means 0.55556C?
Now who is using fractions.?
Also every temp above 33F is also above 32F. If you doubt this consult a math teacher. Or a physics teacher.
I refuse to participate any further in your hijack of this thread.
My hijack? Son not only do you seem to have a reading and math comprehension problem you don’t have a very good memory either.
I have been participating in this thread since post 12 with actual helpful factual information. On the other hand you show up at post 26 with this incredibly useless post
No Sparky you couldn’t sue for a million five as you suffered no loss. What a stupid comment.
Then you went on to double down on your stupidity and complain that your owners manual contradicts itself when it clearly doesn’t.
Now to top it off you say I hijacked the thread. Riiiiiiiiiiight.
Run along Sparky, the adults are talking here.