A/c only works sometimes

Jenrik98

New Member

Apr 6, 2021

16

0

1

St louis, MO

Jul 2, 2022

#1

• Jul 2, 2022

• #1

So ive changed my low pressure switch and the ccrm, and freon is alittle low (shows about 25 psi when compressor off 40 when on and cant get it to take anymore freon,)... ill start car turn on a/c and it works, short cycle but works, drive to store and shut it off to go in, come back out and then the a/c wont come on again, seems like everytime..it works one time then not the next, any ideas? Is it something with turning car off then back on or something to do with once the car gets to operating temp? Any suggestions would be helpful....98 mustang gt 4.6

 

TIGGER

Founding Member

Mar 6, 2000

877

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104

Portland, OR

Jul 2, 2022

#2

• Jul 2, 2022

• #2

My wife’s 96 gt does something similar. I can get in it after work after it has sat for a while, turn on the Ac and it will work perfectly for the 30 mile drive home. If I stop somewhere along the way. It does the same thing you described when I get back in and the car will overheat if I leave the ac on.

My theory is that the ccrm is bad. I have a spare that I know is good but I have not swapped it yet to see if my theory is correct.

 

KRUISR

10 Year Member

Apr 16, 2015

1,857

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Jul 2, 2022

#3

• Jul 2, 2022

• #3

When you say A/C won't come on again, do you mean won't blow cold or won't blow anything at all? I have had it on my F150 where the core in the dash will frost up and not flow any air. Turn it off for a few minutes (letting it thaw) and it works again.

Another thing I was told years ago is turn off the A/C (switch to vent mode) a couple minutes before you turn off the car. It helps prevent shutting down the system with cold refrigerant stuck (not moving) in the system.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,298

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224

Massachusetts

Jul 9, 2022

#4

• Jul 9, 2022

• #4

What’s the high side pressure? Measuring low side doesn’t tell the complete story in terms of charge level.

A rule of thumb is that high side should be 2.5 times ambient temperature.

 

7991LXnSHO

wanna catch the space herp

10 Year Member

Sep 1, 2010

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Kearney, NE

Jul 9, 2022

#5

• Jul 9, 2022

• #5

Mustang5L5 said:

What’s the high side pressure? Measuring low side doesn’t tell the complete story in terms of charge level.

A rule of thumb is that high side should be 2.5 times ambient temperature.

Click to expand...

That’s a lot of pressure for O rings on a hot day.

 

manicmechanic007

5 Year Member

Sep 26, 2017

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Roy, Utah

Jul 9, 2022

#6

• Jul 9, 2022

• #6

If your freon is low, that is the problem
Should have about 80 pounds both sides of a properly charged working system
Fire it up the high side goes 180-450 depending on temp and airflow across the condenser
The low side goes to around 30 and cycles once in a while as the pressure gets to 28 or so
There are tables in the book for cycling rate and time
Yours is low on freon