ok, starting with the basic info, i have a 1990 L98. i am the 2nd owner, and have had the car for a little over 2 years.
the A/C used to work, but i cant remember the last time it did.
i spend so much time deployed/away from home i don't get to work on it as much as i would like.
i do not know vary much about my car's A/C system, and at the moment i dont really have time to read up on it.

so what normally goes wrong with the C4's a/c system?

it blows hot air all day long but i cant seem to get it to cool down. i've tryed recharging the system and it did nothing. im not sure if its the compressor, but if so...$$$ from what i have found on the web.
i have thought about taking to a shop, but i like to work on the car myself, just a hobby. and most of the time its cheaper to do it yourself.

any info would be helpfull, thanks!

 

There is a clutch on the compressor that should engage when you turn the a/c on. If that is not working then you won't get any cooling no matter how much charge you have.

Try turning it on and listening for the click when the A/C engages. If it doesn't turn on then check that all your electrical connections are plugged in tight.

 

........ There is also a pressure switch in the high pressure line that opens the circuit if there isn't enough freon in the system ... it needs approx 60psi to activate the compressor clutch ... this is to avoid burning up the comp if the freon has leaked out ... which is most likely what has happened ... you need to repair the leak(s) first otherwise you're just wasting freon ... you could try charging with leak check freon , it has red dye in it to help locate the leak ... also look at every hose / pipe connection for oiliness and gunk ... that usually indicates where the refrigerant is leaking from ..... the O-rings on the back of the compressor are usual suspects as is the condenser itself ........... Good Luck !

 

Do the easy things first-check for trouble codes!

I assume your car has the C-68 Automatic A/C control head. Most 1990's did. If so you can use it to determine if any trouble codes (among many parameters) have been set.

You press the up and down fan controls at the same time and hold them for ~5 seconds. This will display 00 on the readout. You then press the up or down fan control to cycle through the different choices. Pick one and press the center fan control to display the information.

First the HVAC Diagnostic codes

0 System Faults
(one of these will be set if your air conditioning controls have an LED flashing)
00=No Faults
01= Temp Door Motor Circuit Fault
02= Temp Door Motor Circuit Fault
03 = Ambient Sensor Open
04 = Ambient Sensor Short
05 = In-Vehicle Temp Sensor Open
06 = In-Vehicle Temp Sensor Short
07 = Solar Load Sensor Open
08 = Solar Load Sensor Short
09 = Low Freon Detected
10 = UART Failure


Other Parameters available:

1- Temp Setting 60F to 90F

2- In-Car Temp Sensor 10 = HOT -130 = 230 = COLD

3- Outside Temp Sensor 10 = HOT -130 = 230 = COLD

4- Sun Load Sensor Max light Max Dark
L98 38 183
LT5 115 -110 = 210

5- Ignition System Voltage 0 = 9 Volts -155 = 255 = 16 V

6- Engine Speed (RPM divided by 25)

7- Vehicle Speed

9- A/C System Mode
00 = OFF
01 = Re-Circulation
02 = A/C
03 = Bi-Level
04 = Heater
06 = Defrost
07 = Vent
10 = Manual Re-Circulation

10- Blower PWM 0 = 0 Volts 128 = 14 Volts

11- Program Number 00 = COLD -155 = 255 = HOT

12- Mix Number -155 = 255 = COLD 00 = COLD

16- Coolant Temperature In degrees C

17- Solar Correction 114 = Max light 128 = max dark

30- Stored Full Hot Value 0 to 50

31- Temp Door Travel Range 100 to 200

34- Temp Door Position Requested 00=Full HOT -153=253=Full COLD

35- Compressor On Time 0.1 second increments

36- Number Of Times Below Critical Time

37- Software Version Number

Another major problem with the Corvette A/C is the C-68 control head button's contacts getting dirty causing a failure.

A fairly easy fix:

http://forums.corvetteforum.com/c4-g...on-repair.html


Over 90% of the problems with the control head can be fixed very easily by doing what is described in the link!

This usually fixes the problem. One tip: After you remove the unit and it is on your bench (kitchen table, etc) spread a towel on the surface and place the head on it. Then start your dis-assembly. That keeps tiny screws and parts from rolling onto the floor and getting lost.

 

All good suggestions.Check Youtube.There are step by step videos there that are very easy to understand.I'm not a a/c guru.My advice is to tackle this with confident attitude & check Youtube.If you tell yourself you can't do it or don't know how you will not do it.Its not rocket science.What I think the problem is,is that you have a leak somewhere thats why its not working.Don't be surprised if many things are faulty due to age & lack of usage.A/c parts can be expense as well.Be prepared for this(money).Quick check I do is start car,turn on the a/c & see if the a/c compressor kicks on.If it does but cycles on & off(the clutch on compressor),that normally means a low charge.Feel the a/c lines to see if their cold or hot.Another thing to remember is the smaller lines are the high pressure a/c lines while the thicker lines are low pressure.Also the high pressure lines are normally a solid metal line but can be a metal line crimped onto a hose.Hope this helps.Keep us posted

 

Before you do anything, check the fusible link between the starter and the blower control module right above it.

 

thanks for all the help so far, this is some really good stuff, please keep it coming. ill post again after i do a little work on the car. at the moment, time is not really my friend. im ether at work or sleeping.
also if anyone knows someone in NC i could go to if i cant get it done.

 

Txusaf,
If you are in texas at Ft. Worth i can help you.
Steve

just noticed you are in NC

 

to everyone in Texas, thank you for offering to help me out, i would take y'all up on your offer if i were back home. but that Air Force has other ideas.