Please help with diagnosis. My 1998 C5 has been idle since April, and Air Conditioner has not been used during that time. Now when I call for cold air, the clutch does not engage. Is it possible that the refrigerant has leaked to a point where a relay is keeping the clutch from pulling in? I did check the 10 amp fuze under the hood---it was OK. A relay sits beside the fuze, but I have done no checking on it yet.

I do notice that when I push the AC button on the Automatic Temperature Coltrol Unit, the light on the button flashes several times and then goes off. This happens whether in either the ATC mode or in the Manual mode.

Everything else with the system seems to be working fine----just no cool because the AC clutch wont engage.

Thanks Jesse East

 

Pull your codes using the in dash display and this should point you in the correct direction - or at least give some ppl the info they need to help you.

The instructions to do this have been repeated in 1000s of these posts. But here is one more for good measure: (from Bill's numerous posts)

READING YOUR C5 Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.

There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.

Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.

Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!

NOTE!!! Start the car and let it idle. Then take it for a drive and cause the problem to occur. When you return home pull the codes BEFORE you shut off the engine.


Do NOT discount the codes with the H following them. They can provide an audit trail for issues going on with the car. They ARE important in diagnosing problems.

Post ALL the codes that you pull with the engine running..........

Some codes go away WITHOUT setting an H code when you shut the engine off.

 

Will pull DTC. Thanks

 

I ran the DTC and didnt find anything of interest. I ran the car with AC ON so as to cause a malfunction (lots of hot air), shut it down and checked the codes. There was no HVAC codes. There is a code (P0530) that senses refrigerant pressure----but it did not display in the readout. So I'm guessing I have a malfunctioning clutch.

Maybe I should run the codes while the engine is running and the AC is asking for cold air.......

Thanks Jesse East

 

Still working the problem. The car operator manual says the A/C button will blink if pushed when air conditioning is not allowed. This is happening, so I guess since the clutch is not working the conditions are met for A/C not allowed----and thus a blinking light which turns off when not being pushed.

So Im hoping a new clutch will fix the problem.

Thanks-----Jesse East

 

The pressure switch on the compressor discharge line will not let the compressor engage if the pressure is too low (or too high), so you need to check your freon pressures.
Sounds like freon pressure is too low to allow the compressor to engage.

 

Thanks------Now I'm hoping that a little refrigerant will fix the problem. That will cost much less to repair.

Jesse East

 

It is rare for the ac clutch to go out. That would be one of the last things to check. Check your pressure with gauges don't rely on the code being set sometimes it doesn't set for some reason. Also the outside temp displayed on the control head must be working correctly.

 

Thanks for the Outside Temp Display note.

I dont have gages, so I will have the local shop take a look at the refrigerant levels. I know this guy and trust him to do the work.

 

Thanks for all your suggestions. This is a great support site.

Now I trust my local shop even more. Owner said just get a kit from NAPA and have at it. If that dont fix it, bring it in for more diagnostics.

So, I followed his suggestion, bought the kit (which included a sealer), hooked it up and waited for the first few ozs to flow into system. The compressor clutch began working, so I put about half of the 18 oz can into the system while watching the low side pressure gage to make sure it did not go over 40 psi at the 74 degree ambient temp.

The AC is now putting out cold air. Lets hope Im finished with this little project, which included a new blower motor & fan and a remanufactured AC Digital Display Control Module.

Thanks again. Jesse East