Help! 93 Climate Control No Display, Heater Fan Full On (corrected)

[Cabral]

Just bought a '93 C4 that has been sitting for 6 years. The Automatic Climate Control has no display and the heater-fan is running full on. The buttons are all unresponsive. There is a backlight to the system, so I know it is getting power. I am ready to pull the fan fuse as I am loosing weight. Any ideas?

Sorry for the confusion regarding the year of my Corvette on the previous post.hnoes

 

[mhschaub]

I have a 95 and I attempted to install a daytime running light kit - all was going well until I shorted out the BCM, which caused the traction control to go out and also made the climate control system do what you are describing, including having the fan run constantly. I am afraid that you may have to replace the BCM or have it repaired........

 

[mhschaub]

It's actually the CCM or Central Control Module - it's the one sitting over the battery......

 

[Cabral]

mhschaub-
Thanks for the info. I am curious, besides the fan running full, I get no display at all on the climate control system. Only a back light. Is that what you saw?

I just got a look at a 1993 C4 repair manual (the real 2 book GM deal) Actually, the ECM (engine control module) is the one over the battery. There is one kind-of buried behind the instrument panel called the CCM (central control module). Did you get the ECM or the CCM repaired?

 

[mhschaub]

It's the one over the battery.

What I got was a dashed line in the temp screen and the fan running constantly.

Hopefully this will help. I also had the "sys" notification in the digital speedo screen as well as the traction control going out. I figure if I am going to cook something I might as well go all the way!

 

[Cabral]

Okay now. I smell a slight hint of similarity here. I am getting the same SYS notification in the speedo LCD too. Thanks for your help.

 

[Cabral]

vetteoz-
Great! Another 3 letter acronym. Seriously, I really appreciate this. The BCM should be a lot easier to get to and test.

I think I have a more serious issue. My climate control display is blank. Not like mhschaub, who had a "--" on the screen.

Thanks for you help.

 

[Cabral]

vetteoz-
Not yet. The car is in for a little body repair and paint. I should have it back before Thanksgiving. During this long weekend, I'll be able to begin doing some debugging.

Thanks for the URL to that page.

 

[Cabral]

Success! After getting the corvette back from paint and spending some quality time with her, I figured it out. Here is my process to discovery.

1. Popped out the AC control head and measured the voltage at the connector. It was less than a volt. Good, hopefully this means control head is still good.

2. Went back to the fuse, it was good. Okay...now what?

3. Then I measured the supply voltage side at the fuse and found it was low as well. The voltage to the adjacent fuses: CCM3, Valet and Utility measured low as well. The common voltage supply to these fuses comes directly from the ignition switch when it is switched in RUN. This means that either the ignition switch is faulty or there is a open in the wire coming from the switch to the fuse block.

4. I then removed the driver side knee trim plate hoping to find a loose supply wire or connector. Should be easy to find, these wires are 10GA.

5. Bingo! The connector connecting the ignition switch to the fuse block RUN voltage supply was disconnected and hanging there. Plugged the connector in, switched the ignition to RUN and the AC control head powered up displaying the temp! The blower was not running full-on anymore and all of the AC control head functions seam to work.

Take away...Even if your fuses look good. Check your supply voltages. It may be a problem farther up-steam.

Thanks for everyones support and comments on this one.