A/C on with defrost

You just made this shit up. I can see the benefit, but it's definitely not why it's designed that way.

 

I disagree. Like I said in my reply, when R134 was first introduced, you needed to keep the seal lubricated. Freon used to do that by itself, but R134 requires is a mixture of a refrigerant and a lubricant that separates if not used.

Now, the a/c coming on with the defrost setting just to keep things lubed. . . Probably not the intended function.

 

That isn't true at all. The ECM does run A/C compressors intermittently without activing the dash light. This goes for pretty much every modern vehicle. But that isn't why defrost uses the A/C system.

A/C comes on in defrost mode because dehumidification is a byprodct of the rapid temperature change at the condenser. Therefore unfogging your windows almost instantly vs. heating them up to where water just won't condense on it anymore.

All A\C systems require oil. You're confusing the difference between mineral oil and PAG oil refrigerent compatibility. R134A uses PAG. It comes with it already in it.

Yes, I went to college for HVAC.

 

I was close enough for hand grenades. Sheesh.

Regardless, the point of this thread is to find a mod to NOT do this:

For me, at least until the engine is warm in the winter and probably never the rest of the year.

 

No. All the time. That's why your truck drips water with the A/C on. The condenser has a drain. All systems do this. Your fridge has a drain pan hidden in the bottom and uses compressor heat and the fan to dry it.

 

Please look back at Post 1. Not to stop the a/c system from dehumidifying.

 

Which is fucking stupid. Lol.

 

Maybe for you?

 

Nope lol never saw the point. Thank you . It's my family truckster.

 

I guess. I live in Alaska so... I use defrost a lot. With A/C.

 

I do a lot of things in life but "make shit up" is not one of them. I don't have to. Do your research bro.

 

Lol yes it was! What is the one thing you use in the winter time? I learned it from a Jeep engineer 25 years ago because I had the same question haha. We were at a SAE white paper conference in Vegas.Apparently they were the first to come up with it.

 

It started back in the R12 days. That was the reason, believe it or not. Maybe now they continued it because of the dehumidfier effect but it started to protect the compressor main seal.

 

Our trucks use the new y1234 refridgerant . Ofcourse there is pag oil as well.

 

A/C is pretty much useless weight in western WA.

 

Has anyone found a way to disable the AC during defrost while still having it available if needed (i.e. not just pulling the fuse)? I don't want to get into the debate as to "why would you want to do that?" Bottom line is there are times when you need to dehumidify the inside of the windshield and there are times when you want to heat the windshield up as quickly as possible to melt snow/ice/freezing rain, and I want the choice. Unless the dewpoint inside the truck is greater than the temperature of the windshield, running the AC is pointless. This is my first vehicle where I wasn't able to disengage the AC compressor via the AC button in defrost mode.

I have a Sport with the manual climate control.

 

On 1st gens if you pull off the heat/ac floor-dash knob the shaft will turn 1 more click. This is defrost without ac.

 

Yea. People in the south don't understand the 'frost' in defrost.

 

I’d like to see a mod for this, too. I don’t appreciate the decision to have defrost without A/C taken from me by the Toyota engineers.

Sometimes warm air is all you need; I’ll decide when I want it dehumidified as well.

 

Counterpoint: