BMW Repair: 1987bmw325, snow flake, fuel gauge

Question
1st my fuel gauge fluxuates from full to 1/4 to full when driving.even when it has a full tank.
2nd my a/c is full of r12 but dosn't blow cool air. everything it working like the clutch.someone told me that there is a screen in one of the compresser lines that somtime get cloged.on cool days and at night it will get a bit cool but not cold.during the day forget it dosn't cool anything down.any help would be great
                     thanks vince

Answer
Vincent,
 The fuel gauge is a common problem.  The guage isn't getting good connection, and probably needs to be cleaned.  You can remove the cluster and try to clean the connection points on the guage, sometimes that helps.

 As far as the A/C, how do you KNOW that the lines are full of R12?  Are you listening to what someone told you, or did you fill them yourself.  A/C can be very tricky to get right.  There are some VERY high pressures coming from the compressor, so it's not anything to play with either.  First off, If you're system is full of refrigerant, then the compressor should engage.  Open the hood, stand on the passenger's side of the engine bay, and locate the A/C compressor.  It should be the only thing on the passenger's side of the engine that is turned by a belt.  Have someone press the A/C button (snow flake) and watch to see if the pulley engages.  You will hear a "click" and the engine will idle up a bit.  
 If that is not happening, then you have a bad pressure switch.  The pressure switches are on the reciever-drier, which is located right behind the passenger's side headlight.  There should be several plugs coming out with wires.  One of these is likely bad.

 Since R12 is very expensive, and harmful to the ozone layer, I would suggest having a shop evacuate the system so they can save your R12, have them fix the sensors, then they will put more R12 back in when its done.

 Hope this helps,
 Josh