A/c issue

[djflacoent]

So I'm having a air conditioner issue on my 07 hummer h3. When I first start driving my hummer and then the a/c on it gets cold but 3 minutes down then the cold goes away and gets warm. Also sometimes goes from cold to warm then cold again then warm.

I already did a vacuum on it a few months back.

 

[amrg]

When it gets warm and cold again, are u standing still then moving?

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[Jeepwalker]

Do you have an AC thermostat you can put in the center vents to verify the temperature change? Reason I ask is could there be a grommet that has fallen out of the firewall letting in warm outside air or hot engine compartment air in the cabin as you drive (but the AC still blowing cold)? I had a grommet out on my firewall when I bought it.

Here's where a good scanner could come in real handy to, 1) See if/when the AC clutch was coming on while driving, and 2) View what the HVAC system was doing (vent doors changing). 3) Pressure switch operation?

If the clutch is wearing out it might be slipping. In other words, can't 'grip' as well at higher engine speeds. I'm just throwing out ideas. You should take it to an AC shop for a thorough diagnosis.