Air conditioner on when it shouldn't be.

Your truck is operating as designed and intended. No need to get butthurt.

 

No, he came in here to bitch and preach.

 

I never seen it but I can believe this. I should have said "should not freeze" or "not supposed to freeze".

 

Anyway, I went and did the mod. Took 15 minutes and the A/C works the way it should. Many thanks to O2Duck and CtryBoyInMT. Most others, well...

 

It worked the way it should before you did the mod... now it does not, but it works the way you want it to work.

 

As many have already said, it's not only a defroster but also a defogger. Without the compressor running it's useless to remove fog, it's nothing but a fan blowing humid air. I've driven cars with bad compressors on rainy days, it's no fun.

 

It rather common here in Florida, first sign is a bit of "fog" from the AC vents, then a reduced/no air flow as accumulated frost (rime) blocks the evaporator--My wife's old RAV4 would do this whenever ambient air was very hot and very humid, and she ran the AC in recirculate mode--especially at highway speeds. Turn of the AC and recirculate, let the outside air defrost the evaporator and in 5 to 7 miles all will be well again. The charge was proper on that system but it would freeze up anyway in very extreme heat/RH conditions. A defective expansion valve can cause this too.

Her running in recirculation mode in that weather became one of those "If I had a nickel for every time I told her..." things...

 

The Tacoma has an evaporator temperature sensor. It will turn off the compressor before the evaporator freezes up. I looked to see if there was a minimum ambient temperature for compressor operation, but could not find the value. I doubt the compressor will run when the ambient temperature is below 32 F, but this is not something I can test during warm weather.

On page 535 of the 2016 Tacoma Service Manual, it shows what settings can be changed with the Techstream. You or your dealer can turn off the automatic compressor on with defog or defrost setting. The automatic recirculation mode at maximum cool can also be shut off.

 

Thank you for mentioning this. I hate the auto A/C on defrost of my truck. I came to it from the stone ages (a 1991 Toyota pickup) that I had before it. That let the operator decide, although it didn't have A/C from the factory anyway.

I understand that A/C and fresh air works best but I like to use the defrost setting to keep dust from accumulating as quickly on the windshield when off highway and being dry, dusty and low humidity Colorado sometimes all you need is warm air to melt the snow under the wipers.

You'll notice that if you just tap the wiper stalk on Toyotas there's an intermediate position where the blades will stop a few inches up, which happens to line up with the dash vent. This is invaluable to preventing ice building up under them.

If it can be changed in the computer that's better than the wire mod.

I notice a fair number of people talking about defrosting are in Florida and the midwest, where 'low' humidity is 50%. We don't even hit 100% when it's actively raining.

 

My 95 F350 has AC on every setting except vent., lol

only my 88 Toy 4x4 had an AC switch that only turned on with it.

My 99 would cycle AC on defrost, some days I would wonder why the poor mileage after the EX would change it to defrost.

 

Interesting. I wonder if the 2nd gens can also set this with Techstream. Anyone know?

The "default" settings for A/C and recirculate are quite sensible and given the cluelessness of the average user probably a good idea. But I operate my vehicles in a variety of non-standard conditions and have at least half a brain left (I think) so I often end up fighting with the "idiot-proof" settings. Anyone who has driven past ten miles of high-density feed lots with a vehicle insisting on using outside air will understand why intelligent users might want to override the "optimal" settings. Tunnels are another good example.

 

there have been deaths/accidents from front windshields fogging up when the defrost has been selected while driving using the "old" way. On a similar note the "industry" has changed the way a heater control valve works due to a family freezing to death in a vehicle stuck in a snow bank. The old way to control the heater control valve was to us engine vacuum to open the valve to allow hot coolant into the heater core. When the car slide out of control and hit the snow bank it knocked the vacuum line off the heater control valve, it closed, and the family died due to cold. Similar thing with the AC on in defrost. It was changed due to a problem.

 

I did this on my truck

https://www.tacomaworld.com/threads/a-c-on-with-defrost.7160/page-8#post-2395617

and it has allowed me full control over everything. Quick and easy mod.

 

That's interesting, I dodnt know that. Could come in handy.

 

so let me get this straight....you come on here and ask a question to a "supposed" problem you're having than get a very detailed answer on why it does that and that its working as it should...than you bash and disagree with that gentleman and basically tell him he's wrong? haha.

 

On my 2008 it's a slight bump up towards the mist selection. On my old 1991, which didn't have a mist option, I could get them to stop with a quick on-off of the switch, although sometimes it would take a couple of cycles to time it just right.

 

The even older way the heater control valve worked with with a cable from the dash slider. Same with the throttle. Those continued to work for decades after the truck was built. But they did eventually fray and break, so it wasn't perfect. Didn't need the engine to even run at all to work.

Seems like that family had a bigger issue that eventually they'd run out of gas and it wouldn't have mattered how the heater valve operated. A blanket and a way to start a fire are fail safe options.

 

I think OP got some bad info. @Plain Jane Taco is correct on this and was very polite to OP! Of the dozens of cars I have owned, having the A/C turned on while defrosting the front window was absolutely necessary. If there is lots of frost on the outside, get out and scrape. Extra heat isn't what defrosts the windows since they are full of the moisture, it's removing the moisture that is needed.