Great info here!! thanks guy's for posting this.

 

Great post! New C5 owner here and I've saved this one!

 

I'm hoping someone may have had this same issue. A couple of months ago when I turned the AC on the compressor was quite noisy, turn it off and not a sound from it. It still blew cold air. About 2 weeks ago the noise pretty much went away, maybe a tad noisier than I remember before all of this, but too close to tell. Still blew cold air. About a week ago it started blowing warm to hot air. No H or C codes in the DIC. Compressor engages when turned on. AC light on HVAC remains on and doesn't blink. When it's 85 out is seems as hot, or a little hotter, than ambient temp. When it's 103 out it seems a little cooler than ambient, but I'm only talking about a few degrees.

I'm hoping to get out of this without buying the tool to diagnose, but will if it'll save money in the long run. I have a place that can recharge it for less than I can do it myself.

What do you guys think?

 

Check for codes on your DIC first and post them up.

 

Thank you, but in that post I stated no codes.

 

I pulled my AC down to 200 microns its cold as crap!!!

 

You physically checked the codes using this procedure ? A lot of problems don't throw codes on to the DIC, you have to manually check for them.

The IPC display, the 20-character, vacuum florescent screen above the steering column that says "Corvette by Chevrolet" every time you turn on the key, is a powerful device. DIY Service Techs are going to be most interested in the IPC's ability to show diagnostic trouble codes (DTC) for all the modules that transmit them.
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
3. Press and hold "options" and
4. While holding "options", press "fuel" four times within a 10-second period.
Inititially, the on-board diagnostics go into the "automatic" mode which shows each module's DTCs in a pre-set sequence:
• 10 PCM Powertrain Control Module page 6-357 - 6-361
• 28 TCS Traction Control system ABS on page 5-86
• ?? RTD Real Time damping page 3-136 (I do not have this option)
• 40 BCM Body Control Module page 8-405 UTD Page 8-727
• 60 IPC Instrument Panel Cluster page 8-508
• 80 radio page 8-213
• 99 HVAC Heater Vent-Air Conditioning page 1-118
• A0 LDCM Left Door Control module page 8-904 to 8-951
• A1 RDCM Right Door Control Module page 8-904 to 8-951
• AC SCM Seat Control module page 8-1064 -8-1082
• B0 RFA Remote Function Actuation page 8-676
For each module, all DTCs will be displayed. If none are present in a module, you will see "no more codes" on the ICP display.
There are two kinds of DTCs, "Current" and "History," designated with a letter suffix, "C" or "H". A current code indicates that the malfunction is present in the system whose module is displaying data. A history code indicates a problem existed in that module sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it is possible it's evidence of a previous problem, now solved, that was not removed by clearing codes. More likely is that a history code indicates an intermittent malfunction. "Intermittents" are the most challenging DTCs. An intermittent may have happened only once, may have happened more than once but is inconsistent in its appearance or may be happening on a regular basis but not at the time the IPC is displaying codes. History codes can also be caused by a current malfunction in a system that is not operating at the time DTCs are displayed. An example is the rear window defogger which doesn¹t operate until the BCM detects engine rpm. For history codes set by a system 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 IPC has displayed all 11 modules, the system goes into the manual mode which allows selection of each module using combinations of DIC buttons. The manual mode can also be entered at any time during the automatic sequence by pressing any button except "E/M". Once the IPC displays "manual diagnostics," you may select a particular module by pressing the "options" button to go forward or the "trip" button to go back. Once a system is selected and a DTC is displayed, if more than one are present; press "gages" to move forward or "fuel" to go back.
To exit the diagnostic mode at any time, press "E/M". If you want to erase or "clear" codes, press "reset." Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory.
• 10 PCM Powertrain Control Module page 6-357 - 6-361 Domestic
• A=DTC set immediately and MIL is turned on
• B=MIL turned on after 2 consecutive drive trips
• C=After one failure and stored in History MIL not turned on

 

Yes I did exactly that. No H or C codes for HVAC.

 

That seems strange.

I would flip on AC and verify that fans come on and that the front clutch engages.

If these both work, I would hook up a set of gauges and check your line pressures on both the low and high side.

Might be a bad compressor or possible freon leak.

 

Both fans and clutch engage.

 

Time to check pressures with a guage.

 

I ended up having a code: pcm P0645 H, no current code just the history. Switched the AC and horn micro relay, no cold air. Google tells me it has to do with the sensor.

Static pressure was 150 both high and low. Engine at 2k RPMs, AC max and on recirc low side dropped to about 130 and high side stayed around 150.

I'm guessing it's more likely that the compressor is gone, I'd be REALLY happy if it's just the sensor on the high side. Any insight?

 

More I read the more I think it might need the orifice replaced.

Even more reading and i'm thinking compressor.

 

Saved. Thanks for posting

 

I've read thru all of the posts and really didn't see this question asked and answered. Last year my 98 Vette had just the opposite problem (cooling on passenger side, warm air on driver's side). I took the car to a pretty good shop and they told me that my system was low on freon, they charged it and the A/C worked for about 4 months. Then I had the same problem, the shop recharged the system again for me but they told me it was leaking and would probably need to be repaired. Sure enough a few weeks later I had the compressor replaced. It has been over six months now and today the reverse has happened, cold air on the driver's side and warm to hot air on the passenger side.

I'm guessing that my system is low again but would like to hear if a sensor or something else could cause this problem since this happened very quickly, there was no warm air first (it went straight to "hot air on the passenger side).

I am not good at working on the A/C but want to provide as much insight to the shop when I take it back to them. Any help or suggestions would be appreciated.

Thanks,

Roy in Phoenix

 

LOW FREON can NOT cause both symptoms.

Please read and post your DTCs!

That will tell you what is going on.

READING YOUR 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!!

 

First let me thank you for your quick reply. I wanted to make it clear that I only have one symptom now (warm air from the pass side) and that my 98 is a dual zone A/C. I did have the opposite problem last year but had my compressor replaced and all was fixed for over six months. This new condition just started today.

I will attempt to pull the codes as you have advised, but was wondering if low freon (a leak) could cause the passenger side to blow warm air while the driver's side was blowing cold air.

Thanks for any help or advice.

Regards,

Roy in Phoenix

 

Ok I just pulled the codes and they are as follows:
PCM: No codes
TCS: C1255 H
RTD: no codes
BCM: no codes
IPC: no codes
Radio: no codes
RFA: no codes
SCM: B0851 H
B2605 H
RDCM: B2283 H
B2285 H
U1064 H
LDCM: B2252 H
B2206 H
B2208 H
B2282 H
B2284 H
U1064H
HVAC: B0365 H
B0367 H
B0446 H

There were no current codes showing in any of the modules.

Let me know if you have any information or can recommend actions to take going forward. I still would like to know if low freon could cause my warm air temp on the passenger side.

Thanks again,

Roy in Phoenix

 

Here is the folowup to my cold air driver's side, warm air passenger's side problem. I disconnected the battery and left it for 30 mins then tried to clear all the HVAC codes but every time I cleared the codes and then returned to the diagnostic mode the HVAC codes were back. I then disconnected the battery again and left it overnght. When I reconnected the battery, I cleared the HVAC codes again, this time it appeared to work. I heard the actuators moving (recalculating) and the codes stayed clear. I then started the car and I now have cold air blowing from both sides of the car. I'm not sure what caused this to begin with but I suspect the battery. I have a brand new battery (less than one month old) and think I may have a drain somewhere in the car since the at rest voltage goes from 13.5 volts to 12.55 volts after a few days.

If I determine anything causal, I'll post it here.

Thank you to all of the suggestions on this thread, they really helped.

Roy in Phoenix

 

Glad you got it fixed, hopefully you don't **** off too many of the people using their heaters and hurrying home before it snows today! LOL.