AC Help

[LTLux]

So here's a small ac problem I've been having and cannot figure it out. Before I explain the situation, I have already replaced my blower motor and resistor. I also put in a new control module which is the automatic duel climate control. I also have pulled fusses and relays to try and fix the problem.

My ac works great except when I use it on long trips. I live in Houston and drive to Dallas for work once a month or so. After about 45 min to an hour of use the flow gets cut in half. What I mean is that is does not blow near as hard as it was when the ac was first on. Its still cold but the flow is not there. My high feels like its half what it should be. If I turn the ac off for about 30 sec and turn back on, then its back to blowing full force. I wonder if a flap or door gets shut right above my glove box because I can hear the fan and air but it seems stuck behind the dash. I dont have a problem switching between floor and defrost and vents either. Also, I've noticed that when my ac is on for awhile the recirc button comes on by itself. Is that to prevent the evap from freezing? One last thing, I've noticed that I have a pretty big puddle of water under my car after my car is off. I looked and it seems like my receiver drier is almost freezing and has a huge amount of condesation and thats where all the water is dripping down from.

Does anyone know which actuator is under the passenger side of the dash, to the left of blower resistor? I was going to change it today and I cannot get that 2nd bolt out! I must not have the right tool but I don't see how anything can fit in that tight spot.

By the way, I have an 07 Tahoe LT, if that helps.

 

[LTLux]

Any ideas? I'm at a loss!

I was reading online last night trying to find an answer and it looks like volvos and bmw's have this problem but I did not find an answer.

Some of the things I read said it was normal but I don't think so.

 

[TahoeLTZ2007]

I would guess the A/C is freezing the coil solid.
When you turn it off the system,the coil unfreezes and allows air to flow.

Your drip tube maybe plugged or you have too much refrigerent in system.

Good luck,

Ian

 

[LTLux]

Thanks!

Where is the drip tube? I looked under the car but did not see it.

 

[fire730]

Do you park under trees? Cause like it's been said above it could either be freezing up from being low on freon or the evaporator case could be clogged with leaves. No thanks to GM for making the decision to delete the cabin filter.

Also it may be better to take the recirculate off when you are running for extended periods of time on the highway.

 

[LTLux]

I don't park under trees. I took the blower motor off and reached up there as far as I could. There is a mesh filter or something that had 1 pine straw in it. I also shot a bunch of Lysol up there to kill any mold. AC smells great but flow just gets cut in half after heavy use.

I will take it and have the Freon checked tomorrow.

Where is the drain tube for the ac? I looked under the car but did not see it. As I said, I have a puddle of water under my car after ac use but it all coming from the ac drier. I opened the hood and I can see all the condesation coming from there and dripping to the floor.

 

[fire730]

It should be right under the drier. It's just a pipe sticking out about an inch. And usually it's black so it's real easy to find (sarcasm)!

I'm not 100% on the NNBS but on my NBS it's kinda blocked by the heat shield under the drier.

 

[LTLux]

Do you get to it from under the car or can you check it from above?

 

[fire730]

If it's like a NBS then I think it's fairly easy to remove the heat shield when the truck is cooled off. But I really don't think you can get a finger on it with the shield in the way. I won't be home for hours to even look at my NNBS to see how hard it is to get to.

 

[LTLux]

I found it and you are right, its easy to miss if you dont know where to look. Its not so much the heat sheild but the wheel lining. Just have to push the inside of it to the side a bit and its right below the drier like you said.

I stuck a flat head srew driver up the tube. It was pretty clear but 1 wasp fell out. Can you damage anything by doing that? It felt like something else might have been up there but I think it was the drier itself. I can stick the screw driver about 3 qtrs up the blade of the screw driver and then I hit something. I can stick it in the tube about 3 or 4 inches. Does that sound about right?

 

[fire730]

The evaporator core is in there. So be kinda careful poking in there with anything hard.

 

[jcrack_corn]

what you are describing sounds like the coil is freezing, pretty classic.

due to low refrigerant from pinhole leak.

you should see a nice size puddle of water after you stop it when this symptom has occurred (decreased air flow), vs the normal smaller puddle when this isnt happening.

if you have low refrigerant there is more room for whats left to expand, so it expands faster, making the coil colder, freezing the condensate...as the ice builds, it further compounds the problem by reducing airflow until you have a nice block of ice there.

 

[LTLux]

Thamks for the reply. I'm taking it to get checked in the morning and hope its just low on freon. I will let everyone know, just in case this is going on with anyone else.

Is the only way it gets low through a leak? I assume they will run some dye through the system to check for leaks?

 

[fire730]

Thamks for the reply. I'm taking it to get checked in the morning and hope its just low on freon. I will let everyone know, just in case this is going on with anyone else.

Is the only way it gets low through a leak? I assume they will run some dye through the system to check for leaks?

Yes. It's a sealed system but it eventually leaks somewhere.

Hopefully it's nothing major. Keep us posted.

 

[LTLux]

Well I have it at the shop now and its not low on freon. My compressor is not cycling off like it should to prevent it from freezing up. They are still trying to find out whats causing this problem.

I did tell them that I had recently put in a new head unit for my ac because my buttons were worn down and the paint was flaking off. They think that the new unit may need to be programed. I did have the same issue some have had about the new unit reading outside temp of 55 degrees at first but I unplugged all the connections on the back and then plugged them back in and it was reading correctly. My old unit did not have the outside temp reading on it before so they may be correct.

I'm going to be pissed if I have gone through all this and I caused the problem myself by adding this new ac control unit!

 

[LTLux]

Unreal! It was that damn new ac head unit. It cost me $100 for them to figure that out. They put the old one back in and it made the compressor start disengaging!

Just goes to show you that everything is not just a plug and play. I want to keep the new one in and not go back to the old one, so now I have to go to the dealership and pay $100 to have this one programed.

Sometime these mods kill me!

 

[fire730]

At least you figured it out but damn that sucks. All this electronic BS on these newer vehicles.

My 07s control head was changed at the dealership when they replaced my dash. I wonder if they had to reflash mine. The new head is a little different than the old one cause the old button said "AUX" and the new one says "REAR". But that AC does cool like crazy. I guess I need to make sure it is cycling correctly. That truck really nevers does more than bumper to bumper traffic. So I could have the same problem on an extended highway run.

 

[LTLux]

It does suck. I cant believe its going to cost me $200 to fix something that I caused.

The only good thing is I got my escalade leather shifter in today and its nice. Can't wait to put it in.

 

[LTLux]

Can anyone tell me if there will be an issue getting the new ac module flased at the dealer?

The place I took it to today can flash ac control units but they do it by VIN and since mine is an 07 they said they would have to somehow trick their computer to flash my new one because it has a differnt part number and they did not want to do that.

I have the old module back in now so my compressor cycles on and off but I can tell a differnce in flow and how cold the air is between the two. The newer one that has the "rear" button instead of "aux" and has the outside temp works much better and thats the one I want to put in.

 

[fire730]

Can anyone tell me if there will be an issue getting the new ac module flased at the dealer?

The place I took it to today can flash ac control units but they do it by VIN and since mine is an 07 they said they would have to somehow trick their computer to flash my new one because it has a differnt part number and they did not want to do that.

I have the old module back in now so my compressor cycles on and off but I can tell a differnce in flow and how cold the air is between the two. The newer one that has the "rear" button instead of "aux" and has the outside temp works much better and thats the one I want to put in.

Like I said my 07 LT was replaced with the one that says "REAR" instead so it can be done. But it was done at the dealer so I'm not sure if they reflashed it or not.

I've never noticed it showing the outside temp though.