The green "Auto light" on my climate control system flashes right after start-up, and the A/C compressor won't operate in this condition.

I originally thought this indicated low pressure (Freon), but that checks out OK per my mechanic. Went for quite awhile without any problem, but now it's back. :cry

Of course, removing and restoring electrical power returns the flashing light to a steady condition, and the A/C compressor operates normally until the condition resets to the flashing mode.

Any ideas? I'm :confused:

 

This should help you. It is directly from the dealers service manual.
Good luck.

You can read the HVAC system diagnostic codes from your climate control unit if your 1990 to 1996 Vette is equiped with RPO C68. To enter diagnostic mode, push and hold the fan up arrow and down arrow at the same time until the LCD shows -00 You are now in diagnostic mode and may select any parameter using the up and down arrows. To see the value for that parameter, press the fan "auto" button.

(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

 

That is a help (I had lost this information from the last time).

Problem is, the diagnostic I get is #09 - "LOW FREON DETECTED," but I know the Freon level is OK - had it checked.

 

Are you getting any ECM codes like 66,67,68 or 69?

 

No other Codes that I am aware of.

 

^

 

Your compressor has to be running or at least cycling in order to measure the charge level with a set of manifold gauges. Since you say your's isn't running, I don't know how anyone could tell that's it's properly charged. Remove the protective cover from the accumulator and momentarily depress the schrader valve to see if there's any freon. If so, you can try jumping the pressure switch (on the evaporator outlet - remove the connector and place a paperclip across the terminals to connect the wires) to see if it runs. You then need to measure low and high side pressures with a manifold gauge set with the system operating. If they're normal, then it may just be that the low pressure switch is bad. Suggest you take it to a good a/c shop to have this done or have your mechanic tell you how he determined the charge was adequate. Once you have your operating pressures, should be fairly easy to determine if you need gas, a switch or maybe a new controller, though I doubt the latter is your problem.

 

If the system doesn't run frequently, seals can dry up and cause small leaks in the system and lower the pressure to where the C68 code 09 will display. I was told that low side pressure in these systems is very critical, so only being just a few psi off can set the code. The system only takes about 2 1/4 lbs of R12. You should have the system purged and recharged and add a leak detector. That way, if there is a small leak, it will show up with leak detection equipment.

One trick to keeping the seals tight and everything working properly is to just let the system run in "Auto" mode. Set a desired temp and leave it. I have not really noticed a big drop in gas mileage with the Auto on. The system has much more capacity for heating/cooling than the size of the interior, so it doesn't have to work very long or hard.

 

mfranco, C4cruiser, Suncr...Thanks for all the fine input. It's just what I needed. :)

 

Had a similar if not same problem. The C68 option monitors the cycling time of the compressor. Under low system pressure, compressor cycling will increase. If compressor on time becomes too short, the programmer will signal (flashing light) and software will shut off the compressor until system is recharged/repaired OR battery reset. (for the 90, see page 1C1-20-factory service manual). Once took my 90 to a very good A/C service shop and we had trouble trying to start the compressor to service the AC system. I then remembered this "software shutdown" and we removed the battery cable, pause, and reconnected. Compressor could then be started. Another point to remember about the C68. After disconnecting the power source, it is best to wait 2 minutes before hitting the buttons. The BIT test is moving the mixing door and finding the limits. This takes about a minute and forty seconds so I usually wait 2 and allow it to store all settings before banging the buttons. Now for the really weird stuff. After having the professionals convert the system to 134a, a pressure switch developed a small leak. Enough to cause increased cycling but NOT set the code for low freon pressure, (09 maybe?). That one took some time. Hope this helps.

dlmeyers 90 coupe zf6 3 speed shocks

 

It helps a great deal.

I put up a new post about this (Neat Trick - resetting Codes http://forums.corvetteforum.com/zerothread?id=278642) regarding the need to have the engine RPMs above 1000 after reconnecting the battery cable. If I forgot to do this (by starting and idiling) the code would reset every time.

I find the code (09 - LOW FREON DETECTED) sets every winter after the car has been sitting in storage. The first year this happened i took it ti the dealer who charged me a whole hour of labor :eek: only to write-up the quick fix for resetting the codes.

Maybe I can look at the pressure switch (or elsewhere) to find out why this code set itself each winter.

BUT...the 1000 RPM is a MUST DO to finish the process. :)


[Modified by Airborne, 1:14 AM 4/14/2002]