Chevrolet Repair: 2003 Astro Issues, Help!, electrical issues, setting 3

Question
I have a 2003 Astro that has had some electrical issues.
Most have been repaired but one remains with the AC.
It only blows cool air on blower setting 3, if you try to change the blower setting the cool air will not come out but air does. This has been repaired twice at the dealer with, I believe, a compressor replacement. Now it is going again and dealer says no coverage, guess they dont want to back their work, they only say I have to pay for more diagnostics, which have been paid for twice before.
Previous elec problems were auto door locks locking constantly while driving, interior lights flashing on and off while driving. I cant help but think this is not the compressor, it sounds more electrical related, course what do I know. Nor do I want to put the money out there again if it is going to fail again so quickly
Please help, not getting much help anywhere and getting desperate summers coming!
Any suggestions are welcome and appreciated!!!!

Answer
Hi Melissa,

I used to be a dealership 'wrench'.  I know the game, all too well.  I hated 'hosing' people.  This why I did my own work for a while, and why I try to help here.  

I also don't suspect the compressor.  It works on 3, then it works.  The compressor is being turned off for some reason.  

Does the check engine light come on, or a check a/c light?  Go to a store like Autozone, and have the codes checked.  They do it for free.  

It is possible the pressure is low in the system.  You will need a recharge, if so.  You can do this yourself.  When you put your control at 3, you are calling for a higher cooling demand.  Your system may go to max air, the compressor comes on, even when low, and the system feels cool(er).  But not really cold.  When you demand lower temp, the compressor should cycle but won't, because it is low.  Just a possiblity.  

Go under your hood, and look in the corners for a large silver can.  Usually near the firewall.  If you find it, touch it.  If it is nice and cold, then you are probably good on R-134.  If it is luke warm, coolish, or warm, you are low.  

I am thinking of the reasons why they kept saying compressor.  I really don't think they replaced the compressor.  If so though, and you need one again (for some reason), don't buy their's.  Buy aftermarket rebuilt with a warranty, at a good parts store.  Cheaper and better.

I think you are low on R-134.  I would start there.  

C J S