Originally Posted by 8VETTE7

Electrical issues on the C5 can be very frustrating to chase down. I will state again that you need to get rid of all the NO COMM conditions being reported by the C5 built in code reader. Throwing parts at the symptoms is NOT going to fix the NO COMM conditions and will get expensive very fast...

Here are a couple of links about grounds on the C5. I suggest that you start chasing down ALL the ground locations in the forward part of the car, ie A-Pillar and forward.

http://forums.corvetteforum.com/c5-t...locations.html

http://forums.corvetteforum.com/c5-t...tion-long.html Post #1


https://www.corvetteforum.com/forums...locations.html

Originally Posted by 8VETTE7

No, the BCM is not involved at all with the HVAC system. The automatic climate control system which your car seems to have based on the codes in your first post above has its own control module that is the brain for the HVAC system.

I could post the wiring diagrams but the ones I have are for a 2004 and I am not certain if the diagrams for a 1997 are the same or not. If you want them anyway let me know and I will post them. If there is someone reading this thread and has access to a shop manual for a 97 or 98 perhaps they will post them.

If you have the owners manual for the car I would look up the fuses and relays that are involved with the system and check those fuses and relays as well as the ground points that are relative to the HVAC system from the links I provided earlier. If you do not have an owners manual for your 1997 then here is a link to a PDF of one:

http://www.corvetteactioncenter.com/...97corvette.pdf

Originally Posted by 8VETTE7

Ignition switch could be the issue. In the wiring diagrams for my 04 there are two fuses that power the control module for the HVAC. Both are in the passenger foot well fuse box. Fuse 27 has power at all times and feeds power to the HVAC Control Module on pin C12 of the connector at the HVAC Control Module. Fuse 18 is only HOT in the ON position of the ignition switch and feeds power to HVAC Control Module on pin C5 of the connector. It is a brown wire as you mention. Grounds for the HVAC control module are via pin C1 on the connector to ground splice pack SP202 and then to ground point G202. There are other fuses and relays involved but they relate to the AC compressor clutch and the refrigerant pressure sensor. If you have not already done so verify that SP202 and ground G202 are clean and tight.

You may be able to jumper 12v to the brown wire on the HVAC connector and with the key in the ON position or engine running see if the HVAC will operate. If so then the ignition switch is faulty, a very common issue on the C5. While it is possible to remove and disassemble the switch and clean all the contact surfaces of the switch, I suggest a new ignition switch is the best route if it is bad.


Here is a link to an ignition switch diagnosis procedure that you can also use:

diagnosis

http://forums.corvetteforum.com/1568186703-post64.html


Basically if the voltage at the fuses indicated in the procedure have voltage readings more than about 0.3 volts LESS than the voltage at the battery posts, then the switch is bad. Since there are multiple sensors showing NO COMM there is reason to believe that there is a single cause and the ignition switch certainly provides voltage to the sensors at start up. If that voltage is low then the diagnostics that most sensors go through at power up could fail and NO COMM could result. Lastly if you have not verified the battery do so. A good battery at full charge should have 12.7 to 12.9 volts measured across the battery posts with the NEG battery cable disconnected. A battery voltage of 12.5 or less may cause electronics on the C5 to not function correctly. If the battery is low have it fully charged and load tested.