After AC repairs, when hot outside, AC cycles

[Ryan Swinamer]

I am one of many, many GMC/Chev customers who had an Air Conditioning issue.

My compressor seized up, then burning out my AC clutch, and in all that the feron leaked out.  This happened in the winter.

I replaced my compressor/clutch assembly, the condenser, and the Expansion valve.

We charged it and it worked great!

Until it got warm outside.  Whenever the outside temp gets 26/27C or higher (79/81F) the AC will go in cycles.  It blows cool/cold for a minute or two and then it warms up for several minutes.  This continues to repeat.

I was on a 2hr drive last week, started at 26C, went up to 28C for the first hour and half, the AC did this the whole time.  After the 1.5hr mark, the outside temp fell to 25 and the AC started blowing cold the rest of the trip (30 minutes).

Reversed the drive a few days later, was cold the whole way because the temp never went above 26C.

Checked yesterday with gauges and the High pressure seems to fluctuate between 200 and 325psi, especially when the fans ramp up to deafening speeds.  But the AC was cold the whole time!  Measured temp out of a center vent and it was about 43-44F all the time.  This seemed cold (6-7C).

 

 

I found online where you may have to re-learn your system.  I disconnected the battery for 1.5 hours and then re-connected.

I have also ran the truck with the drivers side at full warm, passenger at full cold.  I ran this for 5-10 minutes and then reversed it for 5-10 minutes.

This was done before the above mentioned trip.

 

I am at a loss.

I am out of warranty, so deal pricing is just so expensive.  I have yet to call GM about possible compensation because of all the issues these trucks are having.  I am not holding breath there.

 

Has anyone seen the above symptoms?  I have done some searching on the forum and haven't seen this symptom yet, but could have missed it.

Thanks!

[Sierra706]

I am one of many, many GMC/Chev customers who had an Air Conditioning issue.
My compressor seized up, then burning out my AC clutch, and in all that the feron leaked out.  This happened in the winter.
I replaced my compressor/clutch assembly, the condenser, and the Expansion valve.
We charged it and it worked great!
Until it got warm outside.  Whenever the outside temp gets 26/27C or higher (79/81F) the AC will go in cycles.  It blows cool/cold for a minute or two and then it warms up for several minutes.  This continues to repeat.
I was on a 2hr drive last week, started at 26C, went up to 28C for the first hour and half, the AC did this the whole time.  After the 1.5hr mark, the outside temp fell to 25 and the AC started blowing cold the rest of the trip (30 minutes).
Reversed the drive a few days later, was cold the whole way because the temp never went above 26C.
Checked yesterday with gauges and the High pressure seems to fluctuate between 200 and 325psi, especially when the fans ramp up to deafening speeds.  But the AC was cold the whole time!  Measured temp out of a center vent and it was about 43-44F all the time.  This seemed cold (6-7C).
 
 
I found online where you may have to re-learn your system.  I disconnected the battery for 1.5 hours and then re-connected.
I have also ran the truck with the drivers side at full warm, passenger at full cold.  I ran this for 5-10 minutes and then reversed it for 5-10 minutes.
This was done before the above mentioned trip.
 
I am at a loss.
I am out of warranty, so deal pricing is just so expensive.  I have yet to call GM about possible compensation because of all the issues these trucks are having.  I am not holding breath there.
 
Has anyone seen the above symptoms?  I have done some searching on the forum and haven't seen this symptom yet, but could have missed it.
Thanks!

Freon level?


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[Ryan Swinamer]

38 minutes ago, Bushleaguechew said:

 

Freon level?


Sent from my iPhone using Tapatalk

 

The low was 26 PSI and solid.  It was the high that would vary so much.

Also, does anyone know the thresholds for the pressure switches?  High and Low?

[Old School Mechanic]

It sounds to me like you have a restriction in the high side. Did you "flush" the system?

When a compressor takes a dump it will leave pieces of it in the system.

If you didn't clean out the evaporator or the lines there still may be stuff in there.

Usually it will gather at the expansion valve, and in the lines running to it, and could cause it to stick and not operate properly.

Pressures should be about 26-29 low side and about 200-250 high side (steady) depending on outside temp.

Max AC, high blower.

Hope this helps

[silveradosid]

was that 26 psi reading you got when the engine was idling

[Ryan Swinamer]

20 hours ago, Old School Mechanic said:

It sounds to me like you have a restriction in the high side. Did you "flush" the system?

When a compressor takes a dump it will leave pieces of it in the system.

If you didn't clean out the evaporator or the lines there still may be stuff in there.

Usually it will gather at the expansion valve, and in the lines running to it, and could cause it to stick and not operate properly.

Pressures should be about 26-29 low side and about 200-250 high side (steady) depending on outside temp.

Max AC, high blower.

Hope this helps

We did not flush the system.

I have been thinking of re-charging, but I guess a flush would be best to do as well.

It is just odd that it works fine until we get to a certain outside temp.

Thanks for the info.

[Ryan Swinamer]

8 hours ago, silveradosid said:

was that 26 psi reading you got when the engine was idling

I believe this was when the AC was working.

When we first connected gauges both high and low were about 77psi, before starting the truck.

[Old School Mechanic]

If you do a flush, make sure to replenish the system with oil also.

You should replace the dryer too.

Your compressor should have come with oil in it, but some will gather in the condenser you replaced, and also the evaporator you are going to flush, and in the dryer. We are talking about a few ounces here.

I assume you vacuumed the system before recharge? If you did you will loose a little there too.

You'll have to look in a service manual to see what the correct amount of oil your system needs.

Try to put exactly the amount of Freon in that is on the label.

By your pressure readings above you may have not got enough Freon in there.

Readings on gauges, not running, will read a little higher than the outside temperature in Fahrenheit.

77 sounds a little low, unless it was cold outside...

Hope this helps