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WHAT IS THE CORRECT PRESSURE FOR MY CAR???

2009 Traverse started blowing warm @ 35k miles. The air was cooler than ambient temp, compressor was rapidly cycling on/off and there was a hissing sound behind the center vents. I freaked out and assumed I would need $1000 in repairs. I bought a AC MANIFOLD GAUGE set so I could properly test low/high pressure. But with the compressor cycling its difficult to read. I added 2 cans of freon and the compressor started to run properly (11 oz freon/can). At this point the air was cooling properly, the compressor was not cycling on/off anymore and the hissing sound went away. I.e. FREON fixed the problems.

But I didnt stop there....
The low side pressure was lower than expected so I added another can of freon and a small can of UV trace so help me find a leak later on. The pressure really didnt change. At that point I packed it up and proclaimed that I fixed the problem. The next morning my wife takes the car and says the ac isnt really working anymore and that the recirculate button cannot be selected.

I SUSPECT THAT I OVERCHARGED THE SYSTEM. Either that... or all the **** freon leaked out overnight.

@ 90 degrees what is the correct low and high pressure?
low 45-55psi
high 250-270psi
Im using a chart found here...
idqusa do t com/faqs/
 

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Service manual is showing for 86-95 degrees F, relative humidity 30-50%

Low side 36-50 psi
High side 219-254 psi

The hissing noise from behind the dash on these vehicles has usually been due to a leak by the evaporator. It means tearing apart the dash in order to get to it. Not an unheard of problem on these vehicles, and even one which took several trips to a dealership before the proper repair was made. Any tracer dye in the system usually will not be seen because of the location of the leak.

Your system has been depleted, and now moisture may have entered it. You may have also lost the oil in the system. Your best bet now unless you are capable of doing A/C work is to take it to a shop. They will have the proper equipment and knowledge to do the work.

Here is one quick search result for "ac hissing" on these forums. There are a lot more posts about the problem.

http://www.traverseforum.com/index.php?topic=2839.0
 

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Start with the cheap approach, UV die that will light up with the UV light revealing leaks. A leak could be in the condenser (stone damage) or elsewhere.
Overcharging an AC system is just as bad as under charging a system. Both will shorten the life of the pump. So lets get this figured out properly.

If there is no sign of leak in the condenser or lines, then you will be right to start to suspect the some hidden part......
 

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ls973800 said:
Service manual is showing for 86-95 degrees F, relative humidity 30-50%

Low side 36-50 psi
High side 219-254 psi

The hissing noise from behind the dash on these vehicles has usually been due to a leak by the evaporator. It means tearing apart the dash in order to get to it. Not an unheard of problem on these vehicles, and even one which took several trips to a dealership before the proper repair was made. Any tracer dye in the system usually will not be seen because of the location of the leak.

Your system has been depleted, and now moisture may have entered it. You may have also lost the oil in the system. Your best bet now unless you are capable of doing A/C work is to take it to a shop. They will have the proper equipment and knowledge to do the work.

Here is one quick search result for "ac hissing" on these forums. There are a lot more posts about the problem.

http://www.traverseforum.com/index.php?topic=2839.0
Highly doubt his system was completely depleted as his Compressor was still cycling on/off as stated. If his pressure was too low it would not cycle on at all. It is likely he has a leak somewhere and as stated the best method to start is the dye test as mentioned earlier. I've worked on A/C systems on 3 vehicles of mine now and it's really not that hard. Typically it's the compressor case seals that go or the evap core as stated. Use the dye to see if you can find it first as tossing cans of r-134a at it is going to get expensive real quick.
 

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compressor was rapidly cycling on/off and there was a hissing sound behind the center vents. I freaked out and assumed I would need $1000 in repairs. I bought a AC MANIFOLD GAUGE set so I could properly test low/high pressure. But with the compressor cycling its difficult to read. I added 2 cans of freon and the compressor started to run properly (11 oz freon/can).

It is not normal for a compressor to cycle on and off rapidly like he said it was. He was low on refrigerant. He added two cans of freon (r-134a I'm sure) and a third can the next day when the low pressure side was still lower than expected. Even with the third can (system only holds 2.3 lbs I believe) his low side pressure still wasn't changed.
 

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ls973800 said:
compressor was rapidly cycling on/off and there was a hissing sound behind the center vents. I freaked out and assumed I would need $1000 in repairs. I bought a AC MANIFOLD GAUGE set so I could properly test low/high pressure. But with the compressor cycling its difficult to read. I added 2 cans of freon and the compressor started to run properly (11 oz freon/can).

It is not normal for a compressor to cycle on and off rapidly like he said it was. He was low on refrigerant. He added two cans of freon (r-134a I'm sure) and a third can the next day when the low pressure side was still lower than expected. Even with the third can (system only holds 2.3 lbs I believe) his low side pressure still wasn't changed.
Yes, but not completely depleted as you stated. If he was completely depleted (especially on the low side) the low pressure switch will not even allow the compressor to kick on. As he stated it was still cycling on and off but rapidly.
 

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Well hopefully he gets it repaired properly without too much additional cost.
 

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Discussion Starter #8
Firstly, let me say that I APPRECIATE YOUR HELP. I have been on several other sites and they are all USELESS compared this this one.

Here is an update... what I am experiencing right now.

Added freon last night. Unsure if I overcharged, even though I have a manifold low/high gauge
Was blowing cold last night
Was blowing warm this morning. The SNOWFLAKE (AC COLD ON) button flashes and shuts off

Hours later... when I came home from work... and car was cold I tested everything again.

83 degrees.........................................LOW......HIGH
CAR ON // AC OFF...............................95........125
AC ON...............................................35........250
AC ON // RADIATOR FANS KICKING ON.....35........200
AC ON //2K RPM..................................20........320

During these reading the AC was blowing pretty good but didnt take temp.

THATS WHEN THINGS GOD WEIRD
Turned off the car for 5 minutes to talk to the wife about what happened this morning.

Turned the car back on. SNOWFLAKE button (AC COLD ON) flashes and shuts off. Blowing warm again. AC cold was off. AC air was on. Gauge was all over the place. Think it even hit 400 on the high side jumping back down when the radiator fan clicked on. Turned the car off for ten minutes and started typing this post. Returned to the car, restarted and retested.

83 degrees.........................................LOW......HIGH
CAR ON // AC OFF...............................80........175
AC ON...............................................35........275 to 300 (until radiator fan turns on)
AC ON // RADIATOR FANS KICKING ON.....35........200
AC ON //2K RPM..................................nt
BLOWING @ 55 degrees :)

So questions are....
1) what should I do now.
2) if I need to remove freon do I remove from the high side or low side.
3) when I store my manifold gauge set should i open the lines to relieve the pressure (if I dont plan to use for a while)
 

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An a/c system, properly functioning and sealed, will not lose freon to evaporation. Like your home refrigerator, it will last indefinately, IF no leaks are within the system.

At this point, evacuate the system with evacuation pump, to remove remaining freon plus any moisture, recharge system with fresh freon, add dye and determine where leak may be.

Keep in mind the additional freon lines , within the Traverse, due to the additional rear evaporator core.
 

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Discussion Starter #10
bobg1951chevy said:
At this point, evacuate the system with evacuation pump, to remove remaining freon plus any moisture, recharge system with fresh freon, add dye and determine where leak may be.

Keep in mind the additional freon lines , within the Traverse, due to the additional rear evaporator core.
Please give me some more detail about the ADDITIONAL FREON LINES? Does that mean there is another LOW/HIGH port
And in regard to evacuating the system.... I dont have access to a vac pump right now. Would you be kind enough to give me your best suggestion as to what to do in lieu of starting completely over again.....
THANKS

After another short break... tested again.
@2k rpm was 20 and 325
Put the gauges on the window so I can read them while holding 2k. After a minute or two.... 325 went high.... and both dials started jumping. Snowflake button not lit. Lost the air.

HERE IS THE DEAL.....
If I need to get a vac I will get one. If I need more freon... i have it already. The only SURE thing is if I bring it to the dealer I will get screwed. So let me know whats WORTH A TRY first... cause ANY of it will be cheaper than the dealer.
 

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There are freon lines that run to the back of the Traverse, along the passenger side of the vehicle.
 

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Discussion Starter #12
Quantum said:
There are freon lines that run to the back of the Traverse, along the passenger side of the vehicle.
I do see the freon lines running under the car. But unsure what I need to do with that info. If you would like to help me... and I do want your help... you need to provide some more info.
 

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mrogge said:
I do see the freon lines running under the car. But unsure what I need to do with that info. If you would like to help me... and I do want your help... you need to provide some more info.
Freon lines to rear = additional evaporator core within right quarter panel, which = additional areas in which to check for leaks.
 

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mrogge said:
Please give me some more detail about the ADDITIONAL FREON LINES? Does that mean there is another LOW/HIGH port
And in regard to evacuating the system.... I dont have access to a vac pump right now. Would you be kind enough to give me your best suggestion as to what to do in lieu of starting completely over again.....
THANKS

After another short break... tested again.
@2k rpm was 20 and 325
Put the gauges on the window so I can read them while holding 2k. After a minute or two.... 325 went high.... and both dials started jumping. Snowflake button not lit. Lost the air.

HERE IS THE DEAL.....
If I need to get a vac I will get one. If I need more freon... i have it already. The only SURE thing is if I bring it to the dealer I will get screwed. So let me know whats WORTH A TRY first... cause ANY of it will be cheaper than the dealer.
Strong statements.
 

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Sounds like a lot of things happening, just have to pin point it down to where it is leaking. Based on the year and the "hissing" sound, I still think it is behind the dash as has been found on many of these models and has been posted on these various forums. I linked to one such post to help in the search for where the leak and noise may have come from, and there are others on these various forums.

Some owners in the past had reported seeing a green substance on the ground or under the car which actually was the dye from the factory in the A/C system. There was a line near the firewall which would rub and wear through, resulting in refrigerant loss. The green dye would show up under the car. Have you ever found any evidence of a leak like this?

The rear does contain an additional evaporator, and there have been leaks in that area from the lines. Usually however, that has not resulted in a noise or hiss from the front dash area.

Sorry I can't be much more help. These are just what I personally would be looking at based on previous posts and the noise you heard. I have only ever "topped" off any of my A/C equipped cars when needed (very seldom) and have never done a major repair to an A/C system myself. I don't have the equipment or knowledge to do so. I would be heading to a shop if I couldn't find something within easy view.
 

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Firstly, let me say that I APPRECIATE YOUR HELP. I have been on several other sites and they are all USELESS compared this this one.

Here is an update... what I am experiencing right now.

Added freon last night. Unsure if I overcharged, even though I have a manifold low/high gauge
Was blowing cold last night
Was blowing warm this morning. The SNOWFLAKE (AC COLD ON) button flashes and shuts off

Hours later... when I came home from work... and car was cold I tested everything again.

83 degrees.........................................LOW......HIGH
CAR ON // AC OFF...............................95........125
AC ON...............................................35........250
AC ON // RADIATOR FANS KICKING ON.....35........200
AC ON //2K RPM..................................20........320

During these reading the AC was blowing pretty good but didnt take temp.

THATS WHEN THINGS GOD WEIRD
Turned off the car for 5 minutes to talk to the wife about what happened this morning.

Turned the car back on. SNOWFLAKE button (AC COLD ON) flashes and shuts off. Blowing warm again. AC cold was off. AC air was on. Gauge was all over the place. Think it even hit 400 on the high side jumping back down when the radiator fan clicked on. Turned the car off for ten minutes and started typing this post. Returned to the car, restarted and retested.

83 degrees.........................................LOW......HIGH
CAR ON // AC OFF...............................80........175
AC ON...............................................35........275 to 300 (until radiator fan turns on)
AC ON // RADIATOR FANS KICKING ON.....35........200
AC ON //2K RPM..................................nt
BLOWING @ 55 degrees :)

So questions are....
1) what should I do now.
2) if I need to remove freon do I remove from the high side or low side.
3) when I store my manifold gauge set should i open the lines to relieve the pressure (if I dont plan to use for a while)
Were you ever able to get a resolution? we are having the same problem.
 
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