Random air conditioning blows hot air

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MAKE: Chevrolet
MODEL: Trailblazer
YEAR: 2002
MILES: 165000
DESCRIBE ISSUE....A/C random blows hot air.

2002 chevrolet Trailblazer LTZ

Electronic dual climate controls

Random A/C issue, 98° ambient going along @ 70mph blowing cold air

And for no reason blows hot air, blower speed & duct location did not change

Stopped & checked the fuses and relays in engine comp & in passenger compartment

Actually swapped each out with known good fuses and relays

At this time compressor was not activating & accumulator was not iced over

Continued on road trip & about 100 miles along A/C just started blowing cold air again.

When I got home I checked the charge with my Robin air 34788NI and found it to be low.02 ounces, so I recovered and recharged to spec. I read Alldata and found there is a low pressure switch tsb issue

Bought the AC Delco switch that is called out in the tsb for randon A/C issue switch did not fix the issue as several days later the A/C randomly blew hot air

I understand there is a HVAC program update but I cannot check it and dealer said bring it in and for $130 they would check it service guy was a bit of a jerk so I will call dealer where car was bought

I would think with the vin # any dealer could look it up?

This car was bought from the original owner & she said if there were any updates and the dealer notified her, updates were done.

I think this is one of those electrical gremlins

Any thoughts or help is much appreciated.

Thank you

Thank you, yes I saw that and that was the irritating part when I called the dealer and all they wanted to do is charge $130 to tell if it is up to date. Do you know if a dealer can look it up or not?
if it was done by an authorized GM dealer it should be in the vehicle service history.
Any GM dealer can search vin # history.

IF and SHOULD are no guarantee -

Update so far 3 more dealers have said bring it in $130 to hook up. I think I am stuck with doing so just to be sure software is at correct level.
I will update when I get this part done.