AC blowing hot air after 5 minutes.. :(

[Detroit Muscle]

HI all, I have a 2003 Envoy SLT I6, this whole summer my vehicle has been blowing hot air with the AC on. Its usually cold for about 5 minutes (compressor spinning), then all hot air for the rest of the day,and the compressor stops. I checked the freon level and it says its full (I added half a bottle anyway) and no difference. Any ideas??
Thanks!

**Sorry been on trailvoy for years, didnt know this site existed!

 

[littleblazer]

First thing is first, have you checked the relays and the clutch itself? These clutches can slip later on in life and removing a shim behind it helps. You could check for voltage at the clutch after it disengages and see. Also I believe the relay is the same as a few others in the under hood box so you could just quick swap them and see.

Also, how does your fan clutch work? A poorly functioning fan clutch will lead to high pressure which will cut the compressor off.

And finally. Welcome aboard.

 

[carshinebob]

My 03 Bravada is doing the exact same thing. Five miutes of air and then warm air after that. I haven't had time to work on it yet. A friend of mine that retired from the Olds engineering garage and worked on hvac systems is coming by for lunch on Friday and we'll figure it out. I'll let you know what we find. ~BOB

 

[Detroit Muscle]

Thanks guys nice to meet you all, thanks blazer ill look into those things, i tested the relay and it still moves the fan.
Sounds good bob let me know!

 

[Tdub]

Try tapping on the front of the ac clutch with something when it is not spinning but it is supposed to. If there is too much air gap, doing so should get it going temporarily.

If you are worried about dropping something into the fan like your fingers, you could just jump the relay with key on engine off, then tap the front with a small hammer and see if the clutch plate sucks in.

 

[littleblazer]

Try tapping on the front of the ac clutch with something when it is not spinning but it is supposed to. If there is too much air gap, doing so should get it going temporarily.

If you are worried about dropping something into the fan like your fingers, you could just jump the relay with key on engine off, then tap the front with a small hammer and see if the clutch plate sucks in.

Good idea.

Also, some mileage would help just in case. Generally higher miles will more lean toward larger air gap. Luckily my ac is always on so it doesn't get the chance to wear out.

 

[Detroit Muscle]

Try tapping on the front of the ac clutch with something when it is not spinning but it is supposed to. If there is too much air gap, doing so should get it going temporarily.

If you are worried about dropping something into the fan like your fingers, you could just jump the relay with key on engine off, then tap the front with a small hammer and see if the clutch plate sucks in.

Sorry but where is the actual clutch for the compressor??

 

[xavierny25]

It's on the face of the compressor pulley.

 

[Redbeard]

The very front. It won't be spinning while the pulley is turning, but may soon be if there is enough pull from the electric to keep it engaged after you tap it.

 

[Detroit Muscle]

got it, thanks dudes, ill check it out after work

 

[Chickenhawk]

Two things. A common failure point is the low pressure switch. Easy to replace.

Also, when you checked the R134a level, what did you use? If you used a gauge on the low side port, what did it read with the compressor spinning and with it not spinning? What was the outside temperature?

You cannot tell the level of Freon in there unless the compressor is engaged. After about 10 years, seals dry up and R134a can leak out slowly. The likeliest cause is just low Freon.

Note that you CANNOT top it up without a good gauge on the low side port and taking readings while the compressor is running. It is also easy to overfill or to wreck the compressor if you don't know what you are doing. This is why we often recommend having it tested and serviced professionally. But that being said, lots of members have topped it up with a can or two if they know what they are doing and are careful. Mine did exactly the same as yours on a very hot and humid day, and I got a good gauge set, added a can and a half and replaced the low side pressure switch. Now working perfectly. I suspect half a can was not enough. (But the gauge will tell you, and its just as harmful to have too much Freon as not enough. Both circumstances will cause the compressor to not engage.)

 

[JerryIrons]

If yo really want to diagnose your own ac, get a set of ac gauges from harbor freight. They are about $50, and can tell you a great deal about how your system is working. They can also tell you how much r134a is in your system, and can be used across many vehicle manufacturers. There are other tools you will need to repair, but a set of gauges are invaluable for at least helping determine whats wrong.

The problem you are describing could have several causes. Low freon, a leak, restriction in system somewhere, faulty switch, problem with compressor, etc. In my own personal experience, a failing AC clutch typically doesn't work right away, but will spin once you get it going by tapping it with a stick of wood.

 

[Detroit Muscle]

Two things. A common failure point is the low pressure switch. Easy to replace.

Also, when you checked the R134a level, what did you use? If you used a gauge on the low side port, what did it read with the compressor spinning and with it not spinning? What was the outside temperature?

You cannot tell the level of Freon in there unless the compressor is engaged. After about 10 years, seals dry up and R134a can leak out slowly. The likeliest cause is just low Freon.

Note that you CANNOT top it up without a good gauge on the low side port and taking readings while the compressor is running. It is also easy to overfill or to wreck the compressor if you don't know what you are doing. This is why we often recommend having it tested and serviced professionally. But that being said, lots of members have topped it up with a can or two if they know what they are doing and are careful. Mine did exactly the same as yours on a very hot and humid day, and I got a good gauge set, added a can and a half and replaced the low side pressure switch. Now working perfectly. I suspect half a can was not enough. (But the gauge will tell you, and its just as harmful to have too much Freon as not enough. Both circumstances will cause the compressor to not engage.)

Well i hooked up a new bottle of freon with the gauge on it and it was already in yellow, the compressor was spinning as I did this on a cool morning

 

[Chickenhawk]

The colors don't matter; it is the PSI reading that is important. Can you hook up the gauge again, and report the reading? Start the engine, make sure ac is on, crank the fan to max and insert the fitting to the port. Let us know what the gauge reads and your outside temperature. This will help us see if you are under or over filled. If the can is still connected to the gauge, make sure the needle piercing valve is screwed down all the way so that you don't start adding more refrigerant. If you can then get someone to rev the engine to 2000 RPM and report that reading as well, that would help.

With the compressor running, you should see 35 to 40 PSI at 70 degrees F. With the engine at idle, it should be closer to 40 and revved to 2000, it should be closer to 35.

Understand this is not 100% accurate, and those gauges can vary widely in their readings. This is only the start. The only true way is to have a professional evacuate the system, and refill with R134a according to the system capacity.

 

[Detroit Muscle]

The colors don't matter; it is the PSI reading that is important. Can you hook up the gauge again, and report the reading? Start the engine, make sure ac is on, crank the fan to max and insert the fitting to the port. Let us know what the gauge reads and your outside temperature. This will help us see if you are under or over filled. If the can is still connected to the gauge, make sure the needle piercing valve is screwed down all the way so that you don't start adding more refrigerant. If you can then get someone to rev the engine to 2000 RPM and report that reading as well, that would help.

With the compressor running, you should see 35 to 40 PSI at 70 degrees F. With the engine at idle, it should be closer to 40 and revved to 2000, it should be closer to 35.

Understand this is not 100% accurate, and those gauges can vary widely in their readings. This is only the start. The only true way is to have a professional evacuate the system, and refill with R134a according to the system capacity.

I see...OK ill have to do that then, i was really frustrated so I added the whole bottle of freon anyways haha

 

[carshinebob]

Mine was the low pressure switch. I don't think there's anything easier to replace under the hood. ~BOB

 

[JerryIrons]

The only true way is to have a professional evacuate the system, and refill with R134a according to the system capacity.

No that's not true. The system capacity of R134a is listed in the service manual, along with a range of high and low pressures expected to be found at ambient air temperature in a normal system. What that means is that if you start with an evacuated system, with fixed parts, you are given the exact amounts of r134a to add. Add close to that amount, and keep an eye on your manifold gauges, and keep adding refrigerant until your ranges are in line with the service manuals. Usually I add enough refrigerant so that I'm at the upper limits, because then my wife will complain about the AC being too cold. Just don't over fill, or you will be fixing it all over again.

This isn't rocket science. But, and it's a pretty big but, half of the AC system is a high pressure side, which can go north of 350 psi, so unless you understand how the system works, which lines are high and low pressure, then yeah maybe a pro would be better. But you know what it's not that hard to understand once you study it a little while. I've fixed my own AC for years, but I have AC manifold gauges, a vacuum pump, UV light, R134a detector, and several parts I built to help diagnose things (like an adapter to hook up low pressure port to my air compressor to provide positive air to locate a leak). All of which were bought at harbor freight, and I probably in one repair saved enough money to buy every tool compared to a mechanic fixing it. I may drive a 13 year old rust bucket beater on occasion, but I refuse to drive it with no AC !

 

[Chickenhawk]

I agree with everything you say, and I have my own gauges too. I also bring in R134a into Canada from Amazon. But I also know the system fairly well and know what to look for. If others don't, they can cause bigger problems than they started with. This is why I may explain what I did but still recommend a professional if they are not too sure what they are doing.

 

[mrrsm]

+1 Here -^- ...and THIS is WHY...

If your SLT is equipped with a Front and Rear Cooling system... The entire charge of R-134A for the system should not exceed 3.00 Lbs. There is no accurate way to know what the A/C system is doing if you cannot graphically see BOTH sides of the system ...both statically, when the system is turned off and the R-134A will redistribute itself and appear balanced and when it is running. Therefor the Prime Tool made for these purposes is that of an Auto A/C Manifold Gauge Set. It gets attached to BOTH the High Pressure Liquid Line (RED) Side and the Low Pressure (BLUE) Returning Vapor Line Side of the system. Once the Engine is running and the A/C is turned on... the Low Pressure Side should drop down to around 70 - 80 PSI and the High Pressure Side should pressurize upwards to around 250-300 PSI if the system is sound and the A/C Compressor and line hardware are operating Nominally.

One of the things that can cause the A/C to appear to function normally for the First (5) Minutes ...and then Blow Hot Air through the Vents will occur if there is any Moisture in the Lines... especially if there is a Leak in the Low Side Lines that will vacuum in Ambient Air that naturally includes Atmospheric Water Vapor that can then travel through the A/C system. When the in-compressible Water Molecules condense inside of the smaller capillary lines of the Evaporator-Expansion Coil ...it can "Flash-Freeze Solid" and plug up the those narrow Liquid Line Capillary Passages and prevent the Refrigerant from continuing on through the system. Hence, there will be the sudden stoppage of the "Cool Air" as soon as the Evaporator Capillary Section is Frozen Up... Weird? ...Yes... But THIS is exactly how it fails.... for a while ...at least until that Frozen Water Blockage Melts ...and then the Cycle repeats itself over and over.

Another Blocking Point can occur happens when the Orifice Tube becomes so completely clogged with junk and dirt from the system internals as to preclude the smooth passage of R-134A through the system. So when either of these two conditions prevail... (or BOTH) then the Hot, Liquefied R-134A exiting the Condenser Coil will begin to back up inside of the Liquid Line side of the system and create a "High Head Pressure" condition in the A/C Compressor... possibly damaging the internal components and seals and cause the Compressor to fail before its time.

The only absolute way in which to know Exactly how much R-134A is presently inside of the system ...is to Recover it as BOTH Vapor and Liquid in a proper, empty and vacuumed A/C Recovery Cylinder. Afterwards, the Recovery Cylinder must be weighed... and the "TARE" weight of the Cylinder gets Subtracted from the Total Weight of that cylinder AND the contents of the recovered R-134A.

Then the theoretically clean system should be vacuumed down to around 25 Microns using a Harbor Freight A/C Two Stage Scroll Vacuum Pump filled to the right level with Recovery Oil in order to completely remove all of that contaminating Moisture... Dirt ...and Non-Condensable Gasses. If the system can hold a decent vacuum without having the needle on the Vacuum Gauge rise above 29" of Mercury and remain below "O" PSIG (14.7 PSI) ... then the 3.00 Lbs of R-134A can be gradually introduced to the point where the Low Pressure Cut-Off Switch stays on and the A/C Compressor can engage and remain running until the balance of the 3.00 Lbs of R-134A is allowed to enter and top off the system. The BEST way to ensure that the Schrader Valves in the Service Ports and the Green "O"Rings will seal up tight and remain so for the life of the system... is to treat them during re-assembly using NYLOG (Blue or Red...It does not Matter) available from Amazon) Here is a video to introduce the stuff to you:

THIS Charging Action should only be done via the Low Side Service Port... and Never as a Pure Liquid by deliberately turning the Can(s) of R-134A UPSIDE DOWN, lest the liquid refrigerant be ingested by the running A/C Compressor ...and Destroy it. The A/C Compressor is designed ONLY to compress R-134A as a GAS... and discharge it as a Hot Liquid after passing through the Condenser Coil... but NO LIQUID REFRIGERANT should ever enter the Low Side of the System during the Charging of R-134A.

So as you can see... there is much to be done to diagnose and correct problems that can occur in so many places within the A/C System that require the Knowledge ...the Skill Set and the Specialty Tools to isolate the problems and perform repairs on any and all of these possible failure points. You simply cannot get there by viewing the "Gauge" on a Can of R-134A and determine these issues.

 

[JerryIrons]

Yep a couple of very good posts. Half the battle is won just by getting a set of AC gauges to diagnose. We need an article submission on repairing AC I think, just to cover the basics. I have a new evaporator sitting in a box, and if I go through the BS of replacing it maybe I'll type one up. It's not a very big leak right now. Unless we already have one and I missed it.

 

[Mooseman]

AFAIK, we don't have one and would certainly be most welcomed.

 

[mrrsm]

I will be the last person to ever discourage anyone from writing a Parallel Write-Up because we continuously can learn from each other so much more when the contributions get refreshed from time to time. Similar to your suggestion... Back in 2010... As my Alter Ego... (60dgrzbelow0) ...I penned a related Complete and Detailed Auto A/C Repair Write UP over at www.60degreev6.com that is still available via this link:

"The Baker's Dozen on How to Repair Automotive Air Conditioning":

http://www.60degreev6.com/vb5/artic...4683-air-conditioning-system-replacement-tips

... and I wrote an abbreviated version here at GMT Nation via this link:

"The Bigger Baker's Dozen on How to Repair Automotive Air Conditioning":

https://gmtnation.com/forums/threads/strange-a-c-issue.11289/page-2#post-503581

 

[Detroit Muscle]

Thanks for all the info guys, but i gave up, lol. I cant figure it out, its getting hot here now, i may just take it in to get diagnosed to see whats wrong, then try fixing myself....but yea, still blowing warm air if its over 70 outside...

 

[Mooseman]

It's been a while! Please do report back what the problem was so it may help someone else.

 

[Dr.Fiero]

And remember to tell the AC pro you take it to what you've done, and what you've put in the system. If you don't - he might just evacuate your system 'per normal' and contaminate (depending on exactly what you put in) his bulk bottle killing hundreds of $'s of his refrigerant.

 

[christo829]

Mine was gradually losing efficiency. It was running tolerably last summer, but not as cold as it used to. This year it just said "NO". Compressor would still run if I told it to (faked the switch, that is), but it was pretty much done. Turned out that both Schrader valves were leaking. Got those replaced and the system properly evacuated and refilled, and it's been going for a few weeks now the way it used to when I first got it.

Hopefully yours is as straightforward a repair!

Chris

 

[mrrsm]

Hurrah NYLOG!

https://www.refrigtech.com/nylog-blue/

 

[Detroit Muscle]

HI all, my AC has been blowing hot air all summer, the compressor clutch only spins when its cool outside and even when it does its for 5 minutes max then it stops and back to hot air. I tried filling the refrigerant up, didnt change anything. So i looked through this forum and several people suggested replacing the AC pressure switch, so I bought a new one, installed it, and nothing, still blowing hot air and compressor clutch not spinning. the past month its been 83 degrees and up. Any ideas or help would be appreciated, thanks all. -Kyle


FYI: 2003 Envoy I6

 

[Detroit Muscle]

Thanks guys, just replaced the AC pressure valve as per several peoples advice on here, didnt do anything Compressor clutch not spinning... Will take it in next week.

 

[Mooseman]

Does it.run for a bit then the clutch starts to slip? Could be the clutch getting weak with a iincreased gap. Remove the clutch shim.

When it's running warm, is there power going to.the clutch? Does the clutch engage when you jump the relay?

 

[Detroit Muscle]

Hmm..how do i remove the clutch shim? This whole week it has never engaged at all, too hot i believe. Not sure if there is power going to the clutch, Ive never attempted to jump the relay, also dont know how lol

 

[JerryIrons]

Harbor freight sells ac manifold gauge set for about $60, and probably cheaper with a discount coupon. If you really want to fix your own ac you'll need a set to show your pressures. There is a lot of info here, including videos of how to jump the relay if you search a bit.

 

[Detroit Muscle]

so I took it in today, the tech claims its the compressor has pooped out Quoted me at $650 for a used one with labor....on cooler mornings the compressor clutch still spins though(for about 8 mins), is it possible to have a bad compressor if the clutch still spins once in awhile??

 

[gmcman]

Have you tried removing the clutch shim? Mine acted the same way about 4 years ago or more, I removed the shim and has been fine since.

Remove the serpentine belt, then remove the center nut on the compressor pulley. Behind the clutch is a small shim on the bolt...worth a try.

 

[Mooseman]

Air conditioner clutch shim removal

 

[gmcman]

Air conditioner clutch shim removal

Thanks for posting that link ...I just woke up and didn't want the OP to be on the hook for a compressor if he didn't need it yet.

 

[Detroit Muscle]

might as well give a shot! weekend project, thanks guys, ill let ya know

 

[JerryIrons]

is it possible to have a bad compressor if the clutch still spins once in awhile??

Yes, I hade a bad compressor turn on and run just fine, but would not compress at all. (high and low pressures were the same when running)

 

[TJBaker57]

I have just reread, browsed really, the thread and nowhere can I find a report of WHAT IS THE PRESSURE. IN PSI. The PSI with compressor running, even if only for a few minutes, is absolutely required for any meaningful diagnosis. Also helpful would be pressure before the compressor runs.

"Added half a bottle anyway" . Having too much refrigerant is as bad as having not enough. Maybe even worse. "More is better" simply does not apply to A/C systems.

 

[JerryIrons]

Yes and I went back and counted my posts, 5 in this thread, 4 of which mention AC gauges and measuring pressure. You can lead a horse to water....