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How many of you run your a/c with the recirculate button pushed in? I'm trying to figure out if my system needs recharging or if its just me. With my old '99 Sierra, the a/c in that made the cab a refrigerator---you basically had to wear a jacket with the a/c on and that was without the recirculate button pushed in. I rarely had to run the a/c on max with that button pushed in, unless it was like 90 degrees. With my Colorado, I have to run the a/c with the recirc button to really get the a/c to blow cold air. Anyone else have to do this?
 

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So what you're saying is that when you push the recirculator button, the A/C blows cold air?
 

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So what you're saying is that when you push the recirculator button, the A/C blows cold air?
It blows cool air without the button pushed in, colder air with it in. To me, that recirculator button is a/c max, and it was rarely necessary in my old truck unless it was very hot (85+ degrees). The dealer seemed to think that the a/c was fine and that I need to run the a/c with the recirculator button pushed in at all times.
 

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Is the compressor engaging when you push the AC button? Did the dealer gauge the AC pressures?
 

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I've posted the same thing...

Some here are happy with the AC.

I'm from South Carolina and the AC in my truck has never been sufficient.
It's been tested several times at various shops.

I've spent summer in the Milwaukee Wisconsin area, Virginia, Massachusetts, western New York state, and North Carolina.
The AC was never cool enough.

Assuming your system is fully and correctly charged, the compressor is probably cycling on/off/on/off/on all the time.

There is a simple popular modification to the cabin temperature control that I've never gotten around to doing, but I will be doing in the next week or two. It involves soldering a 25-cent resistor to the temperature sensing circuit to shift the sensing range.

And you'll be far better off with an electric radiator fan swap.
The OE mechanical clutch fan does OK while moving, but when you're stopped and idling it doesn't move nearly enough air over the AC condenser.

And if you're serious about improving the AC, drop your headliner and install insulation under the roof.
 

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Discussion Starter #6
I've posted the same thing...

Some here are happy with the AC.

I'm from South Carolina and the AC in my truck has never been sufficient.
It's been tested several times at various shops.

I've spent summer in the Milwaukee Wisconsin area, Virginia, Massachusetts, western New York state, and North Carolina.
The AC was never cool enough.

Assuming your system is fully and correctly charged, the compressor is probably cycling on/off/on/off/on all the time.

There is a simple popular modification to the cabin temperature control that I've never gotten around to doing, but I will be doing in the next week or two. It involves soldering a 25-cent resistor to the temperature sensing circuit to shift the sensing range.

And you'll be far better off with an electric radiator fan swap.
The OE mechanical clutch fan does OK while moving, but when you're stopped and idling it doesn't move nearly enough air over the AC condenser.

And if you're serious about improving the AC, drop your headliner and install insulation under the roof.
I think you hit the nail on the head---that explains why the air sometimes feels like it's fluctuating---cold/cool/cold/cool. What's the point of the sensor/cycling routine? :wtf2:
 

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I find my AC is just cool enough to keep me comfortable. It does not get really cold.


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My ac is just no good, just did a recharge and I can honestly say that mine blows colder when the recirculating button is not pushed, plus if you rub on max speed for like 15 min then the blower motor just shuts off completely and will only come on if you shut it off and turn it back on


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I use recirc when I feel like it. Works well either way. If it's 114 and I'm going across town it doesn't matter. The cab is like 243,000 degrees after sitting in the sun. Keeping windows closed on on recirc doesn't exactly cool off very quickly.

What color is your truck? I don't really care what color your ice box Sierra was.

All A/C systems are designed to flow the cold temperature air out of the center vents (as far as I know).
 

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I think you hit the nail on the head---that explains why the air sometimes feels like it's fluctuating---cold/cool/cold/cool. What's the point of the sensor/cycling routine? :wtf2:
It's just an error in the temperature control unit and the overall system design.
I'm no expert in AC systems, there are others here who understand it better than I, but..

The controller has to control the compressor on/off cycles not only in response to cabin temperature but also to avoid freezing the coils and damaging the compressor.
It's processing not only the temperature but also the signal from a refrigerant pressure sensor to maintain the pressure within a minimum and maximum pressure range.

Also in my opinion the cabin blower fan and vents are undersized.

It's a very dynamic thing, given temperature, variation in engine speed, etc.


I'll look up my record of the modification and post links here to the threads where people originally did the experimentation with that mod to the temperature sensor I mentioned before. Some claim they had good success with it.
 

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Discussion Starter #11
I use recirc when I feel like it. Works well either way. If it's 114 and I'm going across town it doesn't matter. The cab is like 243,000 degrees after sitting in the sun. Keeping windows closed on on recirc doesn't exactly cool off very quickly.

What color is your truck? I don't really care what color your ice box Sierra was.

All A/C systems are designed to flow the cold temperature air out of the center vents (as far as I know).
The color of my truck is black, which doesn't help matters any. All the more reason why the a/c needs to work efficiently.
 

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The color of my truck is black, which doesn't help matters any. All the more reason why the a/c needs to work efficiently.
Yep. Same here.
Every summer I ask myself if I was having a psychotic episode the day I bought that truck and chose black.
 

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Yep. Same here.
Every summer I ask myself if I was having a psychotic episode the day I bought that truck and choose black.
I'll deal with it, I guess...especially now that I know what's causing it. I looked at the owners manual and it says the same thing---that the compressor turns on and off "to maximize fuel economy, yet keep the temperature comfortable". We'll see how comfortable it keeps it, I guess. We rarely get above 85 here in Northern NY, and that doesn't happen everyday, its more of a humidity thing than anything else. I'll just have to run it on high fan and recirc button pushed in. If that's one of the few things that I dislike about the truck, I'll live with it.
 

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I don't intend to just deal with it.
Others here live in extremely warm, humid places and have good AC they're happy with.
I'm in Milwaukee at the moment and it's still very cool here.

I plan to be back in Carolina soon and I don't want to spend another summer sweating.
We get days there with 100 degrees and 90 percent humidity.

After you've had the standard AC service and checks and you ensure that your radiator (which includes the condenser) is not clogged with debris, the modification to the temperature sensor is the most effective starting-pointor so I'm told.

The PCM controls the AC compressor based on inputs from a pressure sensor which senses AC system refrigerant pressure, and the evaporator temperature sensor circuit in the cabin.
The key is to readjust the behavior to maximize the compressor on-time without causing system freezeup.

The PCM will stop the compressor if the system pressure is too low (meaning you need more R14), and if the pressure is too high.
Those are absolute limits intended to avoid damage to the compressor, condenser, and evaporator.

That leaves the temperature sensor circuit as the variable that you can play with and modify to increase compressor on-time.
I'll dig into my files to pull up what others have done in this area sometime this weekend and post it.



I have a 4-day holiday weekend and my priority at the moment is installing my gas-spring hood-prop kit, refinishing my Speed grille insert, and gathering parts and materials to install my rear disc brake conversion kit (sometime soon).


.
 

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I switched to an efan over 3 years ago and the AC in my truck works way better than it did with the stock fan. Definetly has more air cooling the condensor.and radiator at idle and low engine speeds.
 

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In my 3 vehicles over the last 25 years, one truck didn't cool well. My 1993 Ford F-150 with black paint. Even in Michigan I complained over a poor system. My ex and I had a new Mustang (silver). Froze you out. My 2003 F-150 (white) perfect A/C. My white Canyon cools just fine too. Even here in California. Once on the road for a while, I leave it on blower #1.

I'm a warm driver, my passengers in the winter wear jackets while I wear a t-shirt. Even worse for me in the summer.

Short trips, it's so difficult to cool off a warm cab. In a normal climate controlled place (building/home) there are certain number of air changes per hour to be efficient and effective. A vehicle left to bake in the sun for hours then trying to force cold air into a closed environment is just not going to cool quickly. No air changes means forcing to cool the hot air that is trapped in the vehicle.

I like to crack a window for a while. My procedure is:
Crank A/C. Windows down to flush the cabin. Even when it's time to just sweat it out while trying to get it cool I'll leave a window cracked. With the fan on higher speeds you're creating a higher presser environment (internally) and the pressure will push the air out the window opening. You may even hear the fan speed decrease when the windows up tightly closed. When I had a rear slider I'd leave that cracked, it worked even better. Air is not drawn in through the rear slider like it is with passenger windows.

Good luck -
 

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I switched to an efan over 3 years ago and the AC in my truck works way better than it did with the stock fan. Definetly has more air cooling the condensor.and radiator at idle and low engine speeds.
AC performance when in traffic or stopped was my primary reason for installing an efan.


...

Short trips, it's so difficult to cool off a warm cab. In a normal climate controlled place (building/home) there are certain number of air changes per hour to be efficient and effective. A vehicle left to bake in the sun for hours then trying to force cold air into a closed environment is just not going to cool quickly. No air changes means forcing to cool the hot air that is trapped in the vehicle.

I like to crack a window for a while. My procedure is:
Crank A/C. Windows down to flush the cabin. Even when it's time to just sweat it out while trying to get it cool I'll leave a window cracked. With the fan on higher speeds you're creating a higher presser environment (internally) and the pressure will push the air out the window opening. You may even hear the fan speed decrease when the windows up tightly closed. When I had a rear slider I'd leave that cracked, it worked even better. Air is not drawn in through the rear slider like it is with passenger windows.

Good luck -
Common sense.
In deep summer in the Carolinas though, yeah you gotta put the glass down to get the ultra-heated stagnant air out, but it's so hot that even that does little good.


Window tint and using one of those windshield shades in the summer will help a lot getting the cab cooled off faster.
Agreed.

In years past GM vehicles, any GM vehicles from the cheapest to the most expensive always had super-effective AC. Always.


Of course the switch from R-12 to R-14 was the beginning of the end for all manufacturers.
With R-14 you need larger everything, especially the condenser and evaporator.

If they would only install insulation under the roof it would make a huge difference.
As it is they depend on the headliner to provide a tiny measure of insulation.
On a hot sunny day you can feel the heat radiating right through the roof + headliner (almost) as if they aren't even there.
Yeah, much of the heat comes through the glass, but the headliner COULD be insulated from the factory, if they weren't so damn cheap.

But with the push for lighter, smaller vehicles...
 

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Discussion Starter #19
AC performance when in traffic or stopped was my primary reason for installing an efan.




Common sense.
In deep summer in the Carolinas though, yeah you gotta put the glass down to get the ultra-heated stagnant air out, but it's so hot that even that does little good.




Agreed.

In years past GM vehicles, any GM vehicles from the cheapest to the most expensive always had super-effective AC. Always.


Of course the switch from R-12 to R-14 was the beginning of the end for all manufacturers.
With R-14 you need larger everything, especially the condenser and evaporator.

If they would only install insulation under the roof it would make a huge difference.
As it is they depend on the headliner to provide a tiny measure of insulation.
On a hot sunny day you can feel the heat radiating right through the roof + headliner (almost) as if they aren't even there.
Yeah, much of the heat comes through the glass, but the headliner COULD be insulated from the factory, if they weren't so damn cheap.

But with the push for lighter, smaller vehicles...
Especially when you own black. It was an oven in my truck today---and the outside temp is only 60 degrees, but the sun is out. It just absorbs that heat like crazy...especially solar heat.
 
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